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236) A 63-year-old accountant is brought to the emergency department after suddenly collapsing at his desk at work. He is unconscious upon arrival but regains consciousness within several minutes. His medical history is significant for stable angina, hypertension, and hypercholesterolemia. He has had no surgeries. His medications include atenolol, simvastatin, aspirin, and a multivitamin. Physical examination is remarkable for paralysis of the upper and lower extremities on the right side. Vibration and position sense are absent on the right side. When the flat of the right foot is stroked with a pen, the right great toe is up going and the other toes fan out. The patient's tongue deviates to the left upon protrusion. Given these findings, a lesion in which region of the brain is most likely?

237) A 60-year-old white male is brought to the physician's office for the evaluation of worsening confusion and memory loss for the past three weeks. His other complaints are muscle twitching and gait problems. He denies any fever, headache or urinary problems. He does not drink nor smoke. His pulse is 82/min, blood pressure is 130/76 mm Hg, and temperature is 37.1°C (98.7°F). He displays poor grooming and is disoriented. The pertinent physical findings are nystagmus and positive extensor plantar response bilaterally. The laboratory studies are as follows: Hematocrit 40%, WBC 6,000/microl, Platelets 160,000/microl. A non-contrast head CT scan is normal. The EEG shows periodic sharp waves. What is the most likely diagnosis of this patient?

238) A 70-year-old retired engineer is brought to the office by his son for a routine check-up. He believes that his son is too greedy and wants all his property. He is accusing his son of "kicking him out of the house to get all of his property." He has been getting more forgetful over the past few years. His younger sibling has the same problem. He has no significant past medical history, except a history of smoking for 6 years when he was young. His blood pressure is 138/78 mm Hg, pulse is 86/min, respirations are 14/min and temperature is 37.0°C (98.6°F). He cannot remember current events, such as the name of the current American president; however, he can still remember past political history. He is unable to concentrate, but is oriented to time, place and person. The neurological examination is nonfocal. CT scan reveals mild generalized atrophy. His HIV and RPR tests are negative. The serum electrolytes and thyroid function tests are normal. What is the most likely diagnosis of this patient?

239) A 54-year-old man comes to your office complaining of recurrent headaches. While observing his gait as part of your neurologic examination, you notice that he very prominently flexes his right hip and knee and his right foot slaps to the floor with each step. Which of the following is the most likely cause of this gait abnormality?

240) A 33-year-old female presents to the office for the evaluation of a one-week history of lightning-like pain on the left side of her face. The pain is very sharp and feels like a burn. An episode lasts for 10 seconds, occurs 10-20 times a day, and keeps her from sleeping, eating, or working. She denies any history of trauma; medication use or recent surgery Vital signs are within normal limits. What is the most likely diagnosis?

241) A 72-year-old woman complains of difficulty "finding the right word" when she is speaking. Her daughter notes that she also frequently complains that her neighbor is stealing her newspapers when this is not the case in actuality. Recently, the patient has been having difficulty balancing her check book as well. On physical examination, her blood pressure is 160/100 mmHg and her heart rate is 90/min. The exam is otherwise unremarkable. Over the course of the next three years, the patient develops a severe memory deficit, and suffers from poor sleep, slowness of movement, shuffling gait and urinary incontinence. Which of the following is the most likely diagnosis?

242) A 32-year-old man presents to your office with blurred vision in his right eye. He denies any pain, ocular discharge, or gritting sensation. Physical examination findings include anisocoria, right-sided ciliary injection, mild ptosis, and impaired right eye adduction. Fluorescein examination reveals a large geographic corneal staining defect. Dysfunction of which of the following nerves is most likely responsible for this patient's impaired corneal sensation?

1) A 40-year-old man is brought to the emergency room because of altered mental status and gait instability. He has had two falls in the last two days. He drinks one pint of vodka daily and smokes one pack of cigarettes daily. His temperature is 35.0°C (95.0°F), blood pressure is 100/70 mm Hg, pulse is 90/min, and respirations are 14/min. He is disoriented, but not in acute distress. You note prominent horizontal nystagmus and conjugate gaze palsy in both eyes and absent ankle reflexes in both legs. His chest is clear to auscultation. Which of the following is the most likely cause of his symptoms?

2) A 16-year-old boy is recommended for admission to the neurology department for rapidly deteriorating clinical symptoms. He is a college student, living in a dormitory. During past week, he was sick. He did not recover fully and during last 3 days, his condition deteriorated. He started to have high fever, terrible headaches. His roommate said he talked about "some foolish happenings" during his high fever, and did not remember what he said later. This morning, he vomited repeatedly and his condition deteriorated rapidly. You examined him and found: febrile man in acute distress with cyanotic pallor, petechiae on his trunk and legs, purpura on his back bilaterally, with cold extremities. He is still alert, but has clammy skin, rapid pulse and labored respiration. His meningeal signs are positive. You diagnose this patient with meningococcal meningitis with systemic progression and you fear that he can develop the Waterhouse-Friderichsen syndrome. What characterizes this syndrome?

3) A 67-year-old Caucasian female presents to your office three weeks after having an ischemic stroke. She complains of transient pain in the right upper and lower limbs that can be induced even by light touch. Her past medical history is significant for hypertension and diabetes mellitus, type 2. Her current medications include enalapril, amlodipine, aspirin, and glyburide. She has right hemianesthesia due to the stroke and mild athetosis of the right hand. The strength is preserved in all four extremities. Hypersensitivity to all kinds of stimuli that induce severe pain reaction is present over the right extremities. Which of the following is the most probable location of the stroke experienced by this patient three weeks ago?

4) A 43-year-old man presents to your office complaining of periodic involuntary head turning and head fixation to the right side. Physical examination reveals a hypertrophied right sternocleidomastoid muscle. What is the most likely diagnosis?

5) A 57-year-old man presents to the emergency department complaining of right arm weakness. He says that he first noticed the weakness two hours ago when he was unable to grip a pen. He is now unable to shake hands and walks with a mild limp. His past medical history is significant for hypertension, diabetes mellitus, and mild headaches over the past several days. He does not smoke or consume alcohol. His blood pressure is 180/100 mmHg, heart rate is 80/min and regular. There is mild asymmetry of the lower face, decreased muscle strength in the right arm, and an extensor plantar reflex on the right side. Sensory examination is normal. Blood glucose level is 210mg/dL. ECG shows sinus rhythm with occasional ventricular premature beats. His urine is negative for ketones and protein. Non-contrast CT scan of the head does not reveal any abnormalities. Which of the following is the most likely cause of this patient's symptoms?

6) A 30-year-old, HIV-positive male, presents with left-sided paralysis of recent onset. His temperature is 37.1°C (98.9°F), pulse is 78/min, blood pressure is 130/80, and respirations are 16/min. The neurological examination reveals loss of recent memory, expressive aphasia, hyperreflexia, hypertonia, and up going plantars on the left side. His current medications include zidovudine, didanosine, indinavir and trimethoprim-sulfamethoxazole. His CD4 count is 70/dl and viral load is 90,000 copies/ml by PCR. The serology is positive for Toxoplasma. CT scan shows multiple, hypodense, non-enhancing lesions with no mass effect in the cerebral white matter. What is the most likely diagnosis?

7) A 64-year-old Caucasian male presents to your office because he has had two falls within the last month. He states that he loses his balance when he tries to turn or stop suddenly while walking. Recently, he says, it has been taking him quite a while to get himself out of bed. He also complains of hand tremors that started last year in his left hand, but that now have been affecting both hands. Which of the following is the best tool to confirm his diagnosis?

8) A 60-year-old male presents to the office and complains of muscle weakness in his extremities. Other accompanying symptoms include progressive difficulty in performing weight-carrying tasks, and a 7 kg (15 lb) weight loss during the last three months. His past medical history is insignificant. He smokes 2 packs of cigarettes daily, and consumes alcohol occasionally. His muscle strength is 3/5 in the proximal muscle groups symmetrically. His reflexes are normal. No sensory abnormality is present. Chest x-ray reveals a right lower lobe ill-defined mass. Which of the following is the most likely localization of the pathologic process in this patient?

9) A 47-year-old obese female comes to the office for the evaluation of recent episodes of mood instability. Her mood varies between sad and irritable. She denies any other symptoms, except for some mild forgetfulness. She tearfully shares that she is convinced that she is going to die, as her father also developed similar symptoms around the same age and died subsequently. On physical examination, writhing movements of the extremities are prominent. This patient's clinical presentation is most consistent with:

10) A 70-year-old Caucasian male is brought to the emergency department due to a sudden onset of right-sided weakness and urinary incontinence about ten hours ago. His past medical history is significant for type 2 diabetes for the last 20 years and hypertension for the last 28 years. On examination, there is 3/5 power in the right upper extremity and 1/5 power in the right lower extremity. Babinski's sign is positive on the right side. The sensations are decreased on the right side of the body, more so in the right lower limb than the right upper limb. Which of the following is the most likely diagnosis?

11) A 32-year-old woman describes five episodes of intractable vomiting over the last year. The episodes last several hours and are associated with a sensation that the room is spinning or tilting. At these times, it is difficult for her to walk because she loses her balance. She cannot relate the timing of the episodes to any particular inciting event. Physical examination reveals stability in the Romberg position and during tandem walk. Proprioception is intact. Dysfunction of which of the following structures best explains this patient's symptoms?

13) A 35-year-old Caucasian man comes to the emergency department at 2 am because of severe pain 'behind the left eye' which woke him up in the middle of the night. The pain is intense and has a stabbing quality. He took ibuprofen at home but didn't get any relief. He denies fever, chills, decreased or blurred vision, cough, nausea or vomiting. He has no other medical problems. He drinks 3-4 bottles of beer daily. He has no known drug allergies. His temperature is 36.7°C (98°F), blood pressure is 120/80 mm Hg, pulse is 88/min and respirations are 14/min. The examination is unremarkable, except for left-sided ptosis and miosis. Which of the following is the most likely diagnosis?

14) A 63-year-old Asian-American woman presents to the ER with a severe right-sided headache that started one hour ago. The pain is located "all around my eye." She has vomited once since the pain began. She also says that bright light aggravates the pain and she complains of seeing "halos" around light. She has never had a headache like this before. Her only medication is trimethoprim-sulfamethoxazole, which she has been taking for the last two days for a urinary tract infection. Her mother has a history of migraine headaches. She does not use tobacco, alcohol, or illicit drugs. On exam, she is afebrile with a pulse of 90/min. Physical exam reveals a non-reactive, dilated right pupil and erythematous right eye. There is lacrimation present. The remainder of examination is unremarkable. Laboratory studies reveal an ESR of 40 mm/hr. Which of the following is the most likely diagnosis?

15) A previously healthy 8-year-old boy is brought to the office by his mother because he has multiple staring episodes. During these episodes, he is unresponsive to verbal or tactile stimuli, and produces lip-smacking movements. Each episode lasts for a few minutes, after which he remains confused for some time. He has no family history of any seizure disorder. His neurological examination is unremarkable. EEG performed before and after hyperventilation is normal. Which of the following is the most likely diagnosis?

16) A 1-year-old female infant is brought to the clinic by his 30-year-old mother due to feeding problems since birth. She still cannot walk nor speak. She began to sit when she was 8 months old. Her weight is in the 15th percentile, height is in the 20th percentile, and head circumference is in the 100th percentile for her age. She has multiple freckles in her armpit and groin area. She has cafe-au-lait spots on her skin, and the diameter of at least 20 of these spots is greater than 1 5mm. What is the most likely diagnosis?

17) A 33-year-old Caucasian female comes to the office and complains of occasional diplopia and ptosis. These symptoms become especially prominent when she looks above her head for some time. She also complains of fatigue in her hands and leg muscles after exercising, such as swimming. Her muscle strength and double vision returns to normal after resting for some time. On examination, lid lag is observed after she is asked to look above her head for some time. No pupillary involvement is seen. The rest of the examination is normal. What is the level of the lesion in the disease that is being described?

18) A 25-year-old, HIV-positive male presents to the office with an altered mental status. He is disoriented, lethargic, and has loss of recent memory. These symptoms have been present for the last month. His current medications include zidovudine, didanosine, indinavir, trimethoprim-sulfamethoxazole and azithromycin. His temperature is 37.7°C (99.8°F), pulse is 78/min, blood pressure is 130/80mm Hg, and respirations are 16/min. The neurological examination is non-focal. His CD4 count is 40/microl and viral load is 25,000 copies/ml by PCR. MRI scan reveals a solitary, irregular, weakly ring-enhancing mass in the periventricular area. The serology for Toxoplasma is positive. PCR of CSF shows EBV DNA. What is the most likely diagnosis?

19) A 33-year-old Canadian female presents to the office with severe, bilateral, lightning-like pain on her face. The pain is burning and sharp in nature, occurs 20-30 times a day, and each episode lasts a few seconds. She is completely incapacitated by this pain. Prior to this event, she had weakness in her left arm, which gradually improved. She denies any history of trauma or drug use. She has no other medical problems. She does not use tobacco, alcohol or drugs. Her blood pressure is 120/80 mmHg, pulse is 72/min, temperature is 36.7°C (98°F) and respirations are 14/min. Complete neurologic examination shows no focal deficits. This type of disorder is most commonly seen in which of the following?

20) A 33-year-old white man with a 9-year-history of progressive-relapsing multiple sclerosis is brought to the emergency department (ED) due to a severe flare-up. He has had several attacks before, and has recovered every time with some residual damage. The last physical examination in his medical records revealed cerebellar symptomatology, a visual defect, and central hemiparesis on the right side. MRI showed multiple, bright, signal abnormalities in the white matter supratentorially on the left side, in the cerebellum, and the left optic nerve. CSF examination revealed an increased synthesis of oligoclonal bands. In the ED, the physical examination reveals paraplegia, bladder and fecal incontinency, and absent sensation from the nipples down. What is the most likely location of this patient's new plaque?

21) A 37-year-old homeless man complains of weakness in his right arm. He says that he was smoking a cigarette when the weakness developed, causing the cigarette to fall from his hand. He also reports having mild headaches, fatigue, and chills over the last week. He admits to regular intravenous heroin use and binge drinking. On physical examination, his blood pressure is 120/70 mmHg and his heart rate is 80/min. There is asymmetry of the lower face, decreased muscle strength in the right arm, and an extensor plantar reflex on the right side. He has multiple needle tracks on his arms. ECG shows sinus rhythm with occasional ventricular premature beats. Urinalysis shows 2+ proteins. Which of the following is the most likely cause of this patient's symptoms?

22) A 45-year-old man comes to the office for the evaluation of excessive wasting of his extremity muscles, which is more apparent on the extensor side. The weakness began distally and asymmetrically. He recently started to have difficulties with swallowing, chewing, and speaking. He feels some movements in his face and tongue. He also has muscle stiffness. His bowel, bladder, cognitive, and sensory functions are intact. The physical examination reveals excessive wasting of his muscles, which is more prominent in the lower extremities. Fasciculation and hyperreflexia of all extremities are noted. His bulbar reflexes are decreased. What neural pathway is most likely damaged?

24) A 67-year-old Asian male comes to the clinic for the first time. He walks very slowly as he enters the room. His chief complaint is "extreme forgetfulness" for the past 6 months. He tearfully shares that he has been "losing sleep." He used to be a very "bright and sharp" person, but is now unable to focus on his daily activities and feels "really extremely low and useless." His past medical history is significant for hypertension, hypercholesterolemia, diabetes, benign prostatic hyperplasia, and TIA. His family history is insignificant, except for Alzheimer's dementia in his father. He does not smoke, and drinks wine only occasionally. He has been living alone for the last 6 months, after his son moved out. His physical exam is normal, except for markedly slow movements. A CT scan of the head is normal. Which of the following is the most likely diagnosis?

25) A 54-year-old construction worker presents to your office complaining of a "funny sensation" in his right arm. He has no significant past medical history. His diet consists of mainly fast food and he drinks one to two litters of soda per day. He does not exercise regularly. He smokes 1½ pack of cigarettes per day. His BMI is 28.5 kg/m2. You ask the patient to stretch out his arms with the palms facing up and close his eyes. Five seconds later you observe the right palm turning inward and downward. Which of the following best explains the observed findings in this patient?

26) A 53-year-old man complains of "shaking" of his right hand. He first noticed this shaking while resting in an armchair and watching TV. He reports that the shaking stopped when he reached for the remote to change the channel. On physical examination, his vital signs are within normal limits and all other organ systems appear normal. Which of the following is most likely responsible?

27) A 60-year-old Hispanic female is brought to the emergency department due to a sudden onset of worsening, left-sided hemiplegia, which was followed by a headache and altered mental status. She was taking her regular morning walk when she developed these symptoms. Her past medical history is remarkable for uncontrolled essential hypertension. She has been a chronic smoker for the last 30 years. The neurological examination shows flaccid paralysis on the left side, and deviation of eyes towards the right side. The CT scan is consistent with a hemorrhagic stroke. Which of the following is the most likely diagnosis?

28) A 70-year-old Caucasian male comes to your office four weeks after experiencing an ischemic stroke. His past medical history is significant for a long history of hypertension, diabetes, coronary artery disease, congestive heart failure, and atrial fibrillation. You noticed that the patient has shaved only the right side of his face. When you ask him to raise his left arm, he raises his right arm. You ask him to fill in the numbers of a clock, and he puts numbers only on the right side. Which of the following areas is most likely affected by the stroke in this patient?

29) A 10-year-old boy is brought to the office by his mother after having a seizure this morning. All he can recall before the episode is "seeing funny little lights." According to his mother, his body went stiff; he lost consciousness, and then had jerky movements of the entire body. He bit his tongue, and started to drool. The seizure lasted for about one minute. After the seizure, he appeared confused for several minutes, and passed urine. He has been complaining of a headache for the past two hours. The neurological examination is normal. What type of seizure did this patient experience?

30) A 56-year-old Hispanic male presents with right-sided arm weakness and speech difficulty. He expresses words slowly and with difficulty. His speech is agrammatic and the melody of speech is abnormal. He is able to comprehend words spoken to him. Which of the following is the most likely site of lesion in the above patient?

31) A 69-year-old man presents to the emergency department with a severe occipital headache, nausea and vomiting for several hours. His medical history is significant for poorly controlled essential hypertension for the last 7 years. The neurologic examination shows ataxia, right-sided facial weakness and deviation of the eyes to the left side. His CT scan is consistent with a hemorrhagic stroke. Which of the following is the most likely diagnosis?

32) A 76-year-old woman presents for a routine medical check-up. Her medical history is significant for hypertension, type 2 diabetes mellitus, and hypothyroidism that are controlled with oral agents. She had a stroke one year ago and has mild residual right arm weakness. Otherwise she has no physical complaints. She is widowed and lives alone. Regarding her memory, she sometimes forgets to return phone calls and take her blood pressure pills. Occasionally during conversations, she has difficulties finding the right word. She drives herself to the grocery market weekly to do her shopping, and has no difficulty managing her finances. She describes her mood as good. She visits her close friends on occasion and often has difficulty falling asleep. Her blood pressure is 135/76 mmHg and her heart rate is 65/min. Finger stick glucose and TSH levels are normal. Which of the following is the most likely diagnosis in this patient?

33) A 59-year-old man is brought to the office by his family due to attitude problems over the last year. He has a history of memory loss and word-finding problems. He has lost interest in golf, which used to be one of his favorite sports. Recently, he has become promiscuous and has started using "dirty language," which he has never used before. He is a non-smoker. He has no significant past medical or surgical history. His uncle had similar features, for which he was admitted into a nursing home, but died soon after admission. The physical examination reveals intact visuospatial functions, intact cranial nerves, and prominent snout and grasp reflexes. What is the most likely diagnosis?

34) A 65-year-old man comes to the physician's office because of frequent falls. For the past 2 months, he has been having increasing difficulty in maintaining balance when walking or standing. He tends to lose his balance on the left side, and feels that his "left body has become weak." He also complains of occasional headaches and nausea for the past 3 months. His other medical problems include hypertension, diabetes mellitus-type 2 and a myocardial infarction 10 years ago. He denies the use of tobacco, alcohol, or drugs. His medications include glyburide, aspirin and enalapril. His vital signs are within normal limits. When asked to get up from the chair and stand with his feet together, he tends to sway to the left, even with his eyes open. When asked to walk a few steps, he walks cautiously and lurches to the left. There is decreased resistance to passive flexion. Which of the following is the most likely diagnosis?

35) A 26-year-old previously healthy white female is brought to the emergency department after having an episode of seizures one hour ago. She has a two-day history of fever and headaches, for which she has been taking acetaminophen and ibuprofen without much relief. She has no family history of seizures. Her temperature is 38.9°C (102°F), blood pressure is 120/70 mmHg, pulse is 110/min, and respirations are 18/min. Complete blood count and CT scan of the head are unremarkable. Her cerebral spinal fluid study shows: Opening pressure 220 mm H2O, Protein 200 mg/dl, Glucose 55 mg/dl, WBC 150/mm3, Lymphocytes 90%, Polymorphs 10%, RBC 200/cmm. What is the most likely diagnosis of this patient?

36) A 64-year-old man presents to the ER with back pain and frequent falls. He also describes difficulty initiating urination. The symptoms started one week ago and have progressed gradually. He was diagnosed with prostate cancer one year ago and treated with radiation therapy. Physical examination reveals weakness of knee and hip extension that is more pronounced on the right. Knee and ankle reflexes are absent bilaterally. Babinski sign is negative. Perianal skin is insensitive to touch but sensation in the anterolateral thigh is preserved. Which of the following is the most likely lesion location in this patient?

37) A 62-year-old Caucasian woman complains of difficulty remembering important dates and appointments. She also describes poor concentration, daytime sleepiness and easy fatigability. She is concerned about her forgetfulness because her mother suffered from recurrent strokes and had severe memory loss. Her father died of chronic leukemia. Her daughter's recent job loss has caused her a lot of stress. She does not smoke or consume alcohol. Her appetite is decreased but she has gained 4 pounds over the last three months. She visited an otolaryngologist for hoarseness of recent onset. She takes over- the-counter laxatives for constipation and occasional aspirin for knee pain. She denies any other medication use. Which of the following is the most likely diagnosis in this patient?

38) A 46-year-old homeless man is being evaluated for frequent falls and a broad-based gait. A single tap on his patellar tendon elicits several to-and-fro leg movements. There is also nystagmus on physical examination. Which of the following additional findings would you expect most in this patient?

39) A 66-year-old female is brought to the office by her concerned son due to increasing confusion, loss of mobility and stiff limbs. She tends to cry out for no reason. She often screams and sees, "a lion roaring in the backyard." She often sees cats in her room, even though her son does not see any. She has significant memory loss. She never had "joint problems" before. She was previously treated with haloperidol, but this only aggravated her rigidity. She is a non-smoker. She has no significant past psychiatric history. In the office, she appears alert, but disoriented and quite agitated. Her blood pressure is 136/72 mm Hg, pulse is 98/min, and respirations are 16/min. Physical examination reveals impaired visuospatial abilities, increased tone, normal reflexes, and coarse resting tremors in the extremities. Her CBC, electrolytes, creatinine, glucose, LFTs, TSH and B 12 levels are within normal range. The serology for syphilis is negative. What is the most likely diagnosis?

40) A 59-year-old obese man comes to the office "to make sure everything is okay." Yesterday after lunch, he experienced weakness in his right upper arm and right lower extremity. He was limping, and his right hand was not strong enough to hold some heavy things. His speech was "somewhat faulty”, and he had a light diffuse headache. By dinnertime, his symptoms were resolving, and when he woke up this morning, his weakness was gone. His past medical history is significant for hypertension, for which he takes atenolol. He has been smoking 1 pack of cigarettes a day for the past 40 yrs. His blood pressure is 150/95 mm of Hg and heart rate is 78/min. The neurological examination is normal. There is a mild carotid bruit on his left side. What is the most likely diagnosis?

41) A 68-year-old woman comes to the office due to the inability to move the right half of her face for the past 24 hours. Her blood pressure is 135/90 mm Hg and heart rate is 76/min. The physical examination is performed. Which of the following signs will exclude the diagnosis of central facial paresis?

42) A 32-year-old construction worker is brought to the emergency room after his co-workers found him confused, disoriented, and bleeding from the nose. His past medical history is unknown. According to his friends, he had been in his normal state of health this morning when he came to work. He then spent the morning moving heavy packages under direct sunlight for several hours. Presently, his blood pressure is 130/90 mmHg, heart rate is 120/min and regular, and temperature is 42°C (108°F). His skin is warm and dry and his neck is supple with no stiffness. His pupils are symmetric, mid-size and reactive to light. Deep tendon reflexes are symmetric and Babinski reflexes are downgoing bilaterally. He moves all four extremities but is unable to speak or follow simple commands. There is active bleeding from the right nostril. Which of the following is the most likely diagnosis?

43) A 65-year-old Caucasian male presents to the emergency department with sudden onset of weakness in his right arm and right leg. He has had episodes of transitory weakness and numbness in his right extremities over the last month, but those episodes used to resolve quickly. He denies headache, nausea, vomiting and loss of consciousness. His past medical history is significant for hypertension, diabetes mellitus, type 2 and myocardial infarction experienced 2 years ago. His current medications are aspirin, metoprolol, enalapril, simvastatin, and glyburide. He does not smoke or consume alcohol. His blood pressure is 160/80 mmHg, pulse is 65/min, temperature is 36.7°C (98°F) and respirations are 14/min. The physical examination reveals right-sided hemiplegia and facial paresis. His speech and praxis do not seem to be impaired. He correctly names his left and right arms. Bedside visual field testing is normal. Head CT without contrast shows no intracranial bleeding Where is the most likely location of the lesion responsible for this patient's condition?

44) A 20-year-old Caucasian male is on mechanical ventilation after sustaining a severe head trauma in a car accident. He is unresponsive to various stimuli. His blood pressure is 100/60mmHg and heart rate is 110/min. After monitoring the patient for six hours, the physician decides to do a bedside assessment of brain death. Which of the following can be observed in a patient with brain death?

45) A 74-year-old woman comes to your office with her husband for a routine check-up. Her husband complains that she often forgets to take her blood pressure pills. He feels that her speech has changed because she occasionally struggles to find appropriate words. Two days ago, she drove to the nearby grocery store and did not find her way back. She has difficulty falling asleep and she always wakes up early in the morning. Her appetite is good. Which of the following is the best indicator of dementia in this patient?

46) A 1-year-old boy is brought to the clinic by his 28-year-old Caucasian mother for the evaluation of his eyes. For the past several months, he has been bumping into objects. His perinatal history is unremarkable. Physical examination of the eyes reveals a bilateral white reflex. The retina cannot be visualized properly. Fundal reflection is absent, and the pupil is white. What is the most likely diagnosis?

47) A 65-year-old white man is complaining of a sudden loss of vision in his left eye which resolved after 15 minutes. "It seemed like a curtain was falling down in my eye!" said the patient. He recalls having a similar episode 3 months ago. His past medical history is significant for hypertension, for which he takes lisinopril (20mg) and hydrochlorothiazide (25mg) daily. His pulse is 82/min, blood pressure is 140/90 mm Hg, respirations are 14/min, and temperature is normal. Fundoscopy reveals zones of whitened, edematous retina following the distribution of the retinal arterioles. What is the most likely diagnosis?

48) A 3-day-old female infant is noticed to have copious, purulent discharge from both eyes. Lid edema and chemosis are also noted. She was born by normal vaginal delivery. Her mother is a 20-year-old primigravida who had no prenatal care. Which of the following is the most likely diagnosis?

49) A 22-year-old Caucasian female presents to the office with several months history of decreased visual acuity and decreased brightness sensation in the right eye. Slight exophthalmos of the right eye is present on physical examination, and ophthalmoscopy shows pallor of the right optic disk. Several cafe-au-lait spots and intensive axillary freckling are present. Which of the following is the most likely cause of this patient's visual problems?

50) A 65-year-old African American man comes to the emergency department due to a sudden loss of vision in his right eye. He has had diabetes, and has been treated with metformin and glyburide for the past 10 years. Visual acuity is reduced to light perception in his right eye, and normal in his left. His vital signs are normal. Ophthalmoscopy reveals loss of fundus details, floating debris and a dark red glow. What is the most likely diagnosis?

51) A 60-year-old woman complains of decreasing vision and a dull ache over her left eye for the past 12 hours. She had a successful surgical cataract extraction in her left eye five days ago. Her blood pressure is 140/90 mmHg, pulse is 92/min, respirations are 14/min, and temperature is 38.1°C (101.7°F). Examination of the left eye reveals a swollen eyelid, edematous conjunctiva, and exudates in the anterior chamber. Testing with Snellen's chart demonstrates decreased visual acuity in her left eye. What is the most likely diagnosis?

52) A 26-year-old male complains of itching and excessive watering of both eyes since this morning. He denies blurring of vision. He uses albuterol inhaler regularly for his bronchial asthma. His vital signs are normal. On examination, both eyes are noted to have conjunctival edema, hyperemia, swollen eyelids, and profuse watery discharge. What is the most likely diagnosis?

53) A 4-year-old boy is brought by his mother to a Medical Camp for the Uninsured for the evaluation of his inflamed right eye. He has had a nasal discharge for the past 10 days. His brother has similar symptoms. His vital signs are stable. There are follicles and inflammatory changes in the conjunctiva of his right eye. The cornea shows neovascularization. What is the most likely diagnosis?

54) A 60-year-old woman comes to the emergency department due to a sudden onset of severe pain in her left eye with blurred vision, nausea, and vomiting. The symptoms began a few minutes ago, while she was watching a movie in a nearby theatre. Her blood pressure is 140/90 mm Hg, pulse is 82/min, respirations are 14/min, and temperature is 98.4°F. Examination reveals decreased visual acuity. Her left eye appears red, with a hazy cornea, shallow anterior chamber, and dilated, fixed pupil. Her left eye is stony hard to touch. What is the most likely diagnosis?

55) A 32-year-old male construction worker presents with complaints of pain, watering, and redness in his left eye for the past 2 days. He reports having similar symptoms in the same eye a few months ago. Examination of his left eye reveals vesicles and dendritic ulcers in the cornea. His vital signs are stable. What is the most likely diagnosis?

56) A 38-year-old man with AIDS (Acquired Immune Deficiency Syndrome) is complaining of diminished vision in both eyes. His CD4 count last month was 50 cells/uL. He has been on highly active antiretroviral therapy for the past several months. He is afebrile, and his vital signs are stable. Ophthalmoscopic examination reveals yellow-white patches of retinal opacification and retinal hemorrhages. What is the most likely diagnosis?

57) A 65-year-old man presents with complaints of decreased vision in both eyes. His visual impairment has been progressively worsening over the past five months. He was diagnosed with diabetes ten years ago. His current medications are metformin and glyburide. His blood pressure is 140/90 mm Hg, pulse is 82/min, respirations are 14/min, and temperature is 98.4°F (36.88°C). Examination shows decreased visual acuity in both eyes. Ophthalmoscopy reveals microaneurysms, dot and blot hemorrhages, hard exudates, and macular edema. Which of the following is the most likely diagnosis?

58) A 69-year-old white male presents to your office complaining of progressive bilateral loss of vision over the past several months. He only has problems with his central vision. His peripheral field and navigational vision are not affected. He denies smoking and alcohol intake. He does not have any history of diabetes or hypertension Two years ago, he had cataracts removed from both eyes. What is the most likely diagnosis?58) A 69-year-old white male presents to your office complaining of progressive bilateral loss of vision over the past several months. He only has problems with his central vision. His peripheral field and navigational vision are not affected. He denies smoking and alcohol intake. He does not have any history of diabetes or hypertension Two years ago, he had cataracts removed from both eyes. What is the most likely diagnosis?

59) An 80-year-old white male comes to the emergency department due to a sudden loss of vision in his left eye that occurred this morning upon waking up. He has had hypertension for the past several years. Current medications include ramipril and atenolol. His blood pressure is 140/90 mm Hg, pulse is 86/min, respirations are 14/min, and temperature is 36.8°C (98.4°F). Examination of the left eye reveals no abnormalities. Funduscopic examination shows swelling of the optic disk, retinal hemorrhages, dilated and tortuous veins, and cotton wool spots. Which of the following is the most likely diagnosis?

60) A 32-year-old woman comes to the office distraught because "the colors look washed out I" She has had this vision impairment since yesterday. She also complains of pain on eye movements. Her vital signs are stable, and she is afebrile. Examination reveals decreased visual acuity, sluggish afferent pupillary response to light, and changes in color perception. Fundoscopy reveals a swollen disc. What is the most likely diagnosis?

61) An 85-year-old man presents with a rash over his forehead, tip of nose and left eye. He also complains of pain and decreased vision. He has had fever, malaise, and a burning sensation around his left eye for the past 5 days. His blood pressure is 140/90 mm Hg, pulse is 92/min, respirations are 14/min, and temperature is 38.1°C (101°F). Physical examination reveals a vesicular rash on the periorbital region and lid margins. The left eye is red, with chemosis of the conjunctiva. Dendriform ulcers are seen on the cornea. What is the most likely diagnosis?

62) A 75-year-old African American man comes to your office for his annual check-up. He is a known diabetic and hypertensive. His medications include lisinopril and atenolol. His vital signs are normal. Examination of his fundus reveals cupping of the optic disc. Visual field examination reveals constricted peripheral vision. What is the most likely diagnosis?

63) A 65-year-old female is complaining of seeing a sudden burst of flashing lights and blurred vision in her left eye. These symptoms started this morning. She now sees small spots in her field of vision. She felt "like a curtain came down" over her eye. She had a successful cataract extraction in her left eye 4 months ago. Her vital signs are stable. Examination shows a sluggish left pupil. Ophthalmoscopy reveals retinal tears and a grayish-appearing retina. What is the most probable diagnosis?

64) A 65-year-old woman presents with complaints of pain and swelling over the inner aspect of her right eye for the past two days. Examination of the eye reveals tenderness, edema, and redness over the medial canthus. Slight pressure over the area causes expression of purulent material. Visual acuity is normal. What is the most likely diagnosis?

65) A 65-year-old man complains of gradual onset blurred vision for the past two months. He also has difficulty driving at night and reading fine print. He has diabetes and hypertension. His medications include ramipril and metoprolol. His vital signs are stable. His best corrected vision is OD (right eye) 20/80, OS (left eye) 20/100, with full fields. Ophthalmoscopic examination with good pupillary dilatation reveals a loss of transparency of lens in both eyes. The red fundal reflex is normal, but retinal details are difficult to visualize. What is the most likely diagnosis?

67) A 35-year-old woman presents with a right-sided red eye for 3 days. She denies pain and notes that she has watery discharge from the eye. She has been coughing and congested for the past 5 days. On examination, the patient has a temperature of 98.4°F, HR of 72 beats per minute, BP of 110/70 mm Hg, and RR of 14 breaths per minute. Her visual acuity is 20/20. On inspection, the conjunctiva is erythematous with minimal chemosis and clear discharge. The slit-lamp, fluorescein, and funduscopic examinations are otherwise unremarkable. The patient has a nontender, preauricular lymph node and enlarged tonsils, without exudates. What is the most likely diagnosis?

68) The local sorority house recently installed a sun-tanning station. Two days later three sorority girls present to the ED with bilateral eye pain, tearing, and photophobia. After ophthalmic anesthesia instillation, a complete eye examination is performed. Visual acuity is normal. Extraocular eye movements are intact and pupils are equal, round, and reactive to light. IOP is normal. Slit-lamp examination is normal, but fluorescein examination under cobalt blue light illuminates small dots throughout the cornea. What is the most likely diagnosis?

69) A 22-year-old man presents to the ED for left eye pain. He was in an altercation yesterday and was punched in the left eye. On examination, his left eye is ecchymotic and the eyelids are swollen shut. He has tenderness over the infraorbital rim but no step-offs. You use an eyelid speculum to examine his eye. His pupils are equal and reactive to light. His visual acuity is normal. On testing extraocular movements, you find he is unable to look upward with his left eye. He also complains of diplopia when looking upward. Funduscopic examination is normal. What is the most likely diagnosis?

70) You are examining the pupils of a patient. On inspection, the pupils are 3 mm and equal bilaterally. You shine a flashlight into the right pupil and both pupils constrict to 1 mm. You then shine the flashlight into the left pupil and both pupils slightly dilate. What is this condition called?

75) A 66-year-old male presents to the emergency department with acute onset of severe chest pain and dyspnea. He localizes the pain to the right upper chest, and says that it is aggravated by deep breathing and coughing. On physical examination, his pulse is 116/min and regular, blood pressure is 110/70 mmHg, and respirations are 22/min. His lungs are clear to auscultation. Chest x-ray is unremarkable. EKG shows sinus tachycardia. CT angiogram of the chest shows a thrombus in the right pulmonary artery. Which of the following is the most likely source of his pulmonary thrombus?

76) A 35-year-old male presents to the emergency room complaining of increasing shortness of breath, fever and malaise for several days. His past medical history is significant for two years of recurrent sinusitis. He is a former smoker and has an occasional glass of wine. His temperature today is 38.4°C (101.1°F), blood pressure is 110/65 mm Hg, pulse is 110/min, and respirations are 22/min. Examination reveals an illappearing male in mild respiratory distress. Patchy rales are appreciated on lung auscultation. Chest x-ray reveals multiple nodular densities bilaterally. His serum creatinine is 2.7 mg/dl and urinalysis shows red blood cell casts. Which of the following would be most helpful in diagnosing his condition?

77) A 64-year-old male presents to the ER with a one-week history of progressive exertional dyspnea. Each of the past two nights he has awakened with a choking sensation and has had to sit up to catch his breath. His past medical history is significant for hypertension and a myocardial infarction two years ago. He takes a baby aspirin and lisinopril daily. His blood pressure is 140/90 mmHg, and his heart rate is 110/min, irregularly irregular. His temperature is 98°F (36.7°C) and his respiratory rate is 24/min. His oxygen saturation is 91% on room air. There is moderate jugular venous distention. Markedly reduced breath sounds are heard over the right lung base. Which of the following most likely underlies this patient's physical findings?

78) A 62-year-old male is brought to the ER after passing out at work. He reports having had difficulty walking over the past couple of days due to an infected wound on his right foot. His past medical history is significant for diabetes mellitus. On physical examination, his blood pressure is 80/40 mm Hg and his heart rate is 120/min, regular. His skin is cold and clammy. Right heart catheterization is performed, and the following readings are obtained: Right atrial pressure 18 mmHg, Pulmonary artery pressure 40/20 mmHg, Pulmonary capillary wedge pressure 9 mmHg. Which of the following is the most likely diagnosis?

79) You are asked to evaluate four different patients, all who have presented with cough and progressive dyspnea. Each has a chest x-ray showing diffuse pulmonary infiltrates. In which of the following patients would bronchoscopy with bronchoalveolar lavage be most likely to yield a diagnosis?

81) A 54-year-old man is being evaluated for shortness of breath. Examination shows dullness to percussion and increased breath sounds, particularly during expiration, in the right lower lobe. Cardiac examination reveals regular rate and rhythm with normal S1 and S2. There is no murmur. Moderate peripheral edema is present. Which of the following is the most likely cause of his shortness of breath?

82) A 15-year-old male comes to your office with a one-week history of fever, non-productive cough, sore throat and headaches. Today he noticed a skin rash. His temperature is 38.5°C (101.3°F), pulse is 90/min, blood pressure is 115/78 mm Hg and respirations are 16/min. His throat is hyperemic, but there is no cervical lymphadenopathy. Chest auscultation and percussion reveal no abnormalities. You note dusky red, target shaped skin lesions over all four extremities. Chest x-ray reveals interstitial infiltrates in the left lower lobe. Sputum gram stain reveals polymorphonuclear cells but no organisms. Which of the following organisms is most likely responsible for this presentation?

83) A 53-year-old man presents with two episodes of hemoptysis over the last week. He describes a preceding two-year history of morning cough productive of approximately one tablespoon of yellowish sputum. During the last week his morning cough was accompanied by a small amount of blood on two occasions. He denies any dyspnea, fever, chest pain, or weight loss. He has been smoking for 30 years but has tried to cut down recently. He works in construction. His only medication is ranitidine for occasional heartburn. Which of the following is the most likely cause of his hemoptysis?

84) A 60-year-old Caucasian man comes to the physician because of a productive cough and dyspnea on exertion. He denies hemoptysis, chest pain, and leg swelling. He has smoked one-and-a-half packs of cigarettes daily for 40 years and drinks 2-ounces of alcohol daily. He has worked in a shipyard for 10 years. His temperature is 37.2°C (99°F), blood pressure is 140/80 mmHg, pulse is 80/min, and respirations are 20/min. His chest x-ray shows prominent bronchovascular markings and mild diaphragmatic flattening. His pulmonary function testing shows decreased FEV1/FVC ratio and normal DLCO. Which of the following is the most likely diagnosis?

85) A 47-year-old smoker presents to the emergency room with a three-day history of shortness of breath and cough. His past medical history is significant for tuberculosis ten years ago, treated with six months of a multidrug regimen. On exam today, his blood pressure is 140/90 mmHg and his heart rate is 110/min. Breath sounds are decreased over the right lung base. Over the same area there is dullness to percussion and increased fremitus. The patient also has trace ankle edema. Which of the following most likely accounts for these findings?

86) A 51-year-old man develops acute respiratory distress syndrome (ARDS) while hospitalized for acute pancreatitis. On his third day in the intensive care unit, he is sedated, intubated, and ventilated with a PEEP (positive end-expiratory pressure) of 15 cm water and Fi0 2 of 0.6 (60%). Suddenly his pulse increases from 100 to 140/min, systolic blood pressure drops from 120 to 90 mm Hg, and central venous pressure increases from 10 to 15 cm water. On chest auscultation, breath sounds are absent on the left side. Which of the following is the most likely explanation for this sudden deterioration?

87) A 27-year-old male presents to you with complaints of cough, chest discomfort and dyspnea on exertion. He says that he has lost 10 pounds over the past 2 months. He has been smoking 1 pack per day for the past 10 years. He drinks 2 beers every weekend. He denies illegal drug use and has not had multiple sexual partners. Physical examination is unremarkable. Chest x-ray reveals a large anterior mediastinal mass. Blood work reveals that he has elevated levels of HCG and alpha-fetoprotein (AFP). What is the most likely diagnosis?

89) A 42-year-old man presents to his primary care physician complaining of daytime sleepiness. He says that he often falls asleep during meetings, watching TV, and even while driving his car. He does not feel refreshed after his daytime naps, and has not experienced vivid hallucinations when falling asleep or upon awakening. He has occasional morning headaches and his wife complains that he sometimes keeps her up at night. Physical exam reveals a body mass index (BMI) of 31.3 kg/m2. An arterial blood gas is normal. What is this patient's most likely diagnosis?

90) A 34-year-old male is rushed to the emergency room with severe respiratory distress. He is agitated and gasping for breath. He has been seen in the ER several times before for difficulty breathing, food intolerances and skin allergies. Physical examination is notable for excessive accessory respiratory muscle use, retraction of the subclavicular fossae during inspiration, and scattered urticaria over the upper body. What is the most likely diagnosis?

91) A healthy 36-year-old Caucasian woman comes to the physician because of dyspnea on exertion. She has no other medical problems. She does not use tobacco, alcohol, or drugs. Her father has prostate cancer and her mother had a stroke. She takes no medication and has no known drug allergies. Her temperature is 36.7°C (98°F), blood pressure is 140/90 mmHg, pulse is 84/min, and respirations are 22/min. Examination shows clear lung fields. Her chest x-ray shows prominent pulmonary arteries and an enlarged right heart border. EKG shows right axis deviation. Which of the following is the most likely diagnosis?

92) A 65-year-old male comes to the physician because of fever, chills, and productive cough. The symptoms started four days ago. He also complains of chest pain, which increases with inspiration. He has smoked one pack of cigarettes daily for 45 years. He drinks 3-4 ounces of alcohol daily. His chest x-ray showed an infiltrate in the right upper lobe. The sputum examination of the patient reveals capsulated gram-negative bacilli. Sputum culture is growing mucoid colonies. Which of the following is the most likely causative organism in this patient?

94) A 59-year-old male is brought to the emergency department with severe dyspnea and left-sided chest discomfort. He says that he was driving to work when he began to feel suddenly weak and short of breath. He has a long history of chronic obstructive pulmonary disease, esophageal reflux and chronic pyelonephritis. He smokes one pack of cigarettes per day. His current medications include ranitidine and inhaled ipratropium and albuterol as needed. Physical examination reveals trace ankle edema, decreased breath sounds over the left chest and scattered wheezes over the right chest. ECG shows sinus tachycardia. Arterial blood gas analysis is given below: pH 7.42, pO2 59 mmHg, pCO2 41 mmHg. Which of the following most likely underlies this patient's current condition?

95) A 32-year-old man with a known history of recreational drug abuse is found by a friend on the floor of his apartment. There is a pool of urine around him. He is confused, not oriented to time or place, and does not recall recent events. His blood pressure is 110/70 mmHg and his heart rate is 120/min. He talks and moves all his extremities. His laboratory findings are the following: Hemoglobin 15.2 mg/dl, WBC 12,500/mm3, Platelets 160,000/mm3, Sodium 136 mEq/L, Potassium 5.1 mEq/L, Creatinine 1.1 mg/dl, AST 35 units/L, AL T 40 units/L, Alkaline phosphatase 70 units/L, CPK 26,000 units/L. His urine toxicology screen is positive for cocaine and cannabinoids. The patient is at the greatest risk of which of the following?

96) A 52-year-old nursing home worker presents with a four-week history of non-productive cough and night-time sweating. She also reports having unintentionally lost five pounds over the last month. Her medical history is significant for a mastectomy for left-sided breast cancer five years ago and hepatitis C for which she does not take treatment. She says she was last tested for HIV 6 months ago and the test was negative. She takes no medications currently. She emigrated from Mexico two years ago. She smokes one pack of cigarettes daily and consumes two bottles of beer every weekend. Chest x-ray shows a right upper lobe cavity with surrounding infiltration. Which of the following is the most important epidemiologic clue to the etiology of this patient's disease?

97) A 44-year-old obese Asian immigrant presents to the ER complaining of a persistent cough for about 3 months. He denies any fever, chills, runny nose or sputum production. He does complain of dyspnea on exertion, which also has been of a short duration. He says that over the last year, he has become progressively short of breath and is unable to sleep lying down. He denies any chest pain or diaphoresis, but has had palpitations in the past. He does not smoke or drink alcohol. On examination, he is alert and in mild distress. He has a BP of 110/70 mmHg, pulse 100/min and is afebrile. Auscultation is difficult. The chest-x ray reveals an enlarged cardiac silhouette. It appears that the left main stem bronchus is elevated. There is no other lung pathology visible. The ECG shows irregularly irregular rhythm. The pathophysiology of this condition is related to which of the following?

98) A 72-year-old white male with a past medical history of hypertension, hypothyroidism, and coronary artery disease presented to the physician's office because of fever, malaise, nonproductive cough, and shortness of breath. His temperature was 38.3°C (101°F). His chest x-ray showed a patchy right lower lobe infiltrate. He was sent home on oral amoxicillin. Four days later, the patient was brought to the emergency room because he was having continuous fevers, headache, pleuritic chest pain, and abdominal pain. He appears confused. His blood pressure is 120/70 mmHg, pulse rate is 100 per minute, respiratory rate is 24 per minute, and temperature is 38.9°C (102°F). His chest x-ray showed consolidation of the right lower lobe. Which of the following is the most likely cause of this patient's pneumonia?

100) A 56-year-old woman is brought to the emergency room with shortness of breath, which she says began suddenly two hours ago while she was enjoying her favorite television show. She also reports the simultaneous onset of sharp, left-sided chest pain. Her previous medical history includes diabetes mellitus for the past 10 years and hypertension for the past 6 years. Her family history is significant for heart disease in her father, who died at age 40. Her medications include enteric-coated aspirin, captopril and glipizide. She has a 30 pack-year smoking history, but does not smoke currently. On physical examination, she is in acute distress and is sweating profusely. Her temperature is 38.0°C (100.5°F), pulse is 140/min and irregular, respiratory rate is 30/min, and blood pressure is 110/60 mm Hg. Her oxygen saturation is 84% on room air by pulse oximetry. Jugular venous pressure is within normal limits and her lungs are clear to auscultation. Serum analysis reveals the following: Hematocrit 40%, WBC count 11,600/mm3, Platelet count 190,000/mm3. Chest x-ray is unremarkable. ECG reveals irregular RR intervals, with no definite P waves and narrow QRS complexes. Which of the following is the most likely cause of her current symptoms?

101) A 42-year-old white male presents to your office complaining of periodic breathing difficulty and wheezing. He visited an otolaryngologist for persistent nasal blockage recently. His past medical history is significant for unstable angina experienced five months ago. His current treatment includes aspirin, diltiazem, and pravastatin. He does not use tobacco, alcohol, or drugs. His vital signs are within limits. What is the most probable cause of this patient's respiratory complaints?

103) A 43-year-old moderately overweight woman presents to the emergency department complaining of two days of shortness of breath. Today, while climbing stairs, she had an episode of severe lightheadedness and near syncope. Her medical history is significant for a right calf deep venous thrombosis one year ago. She takes no medications currently. On physical examination, her blood pressure is 90/50 mmHg and her heart rate is 120/min and regular Imaging studies are most likely to reveal which of the following?

104) A healthy 33-year-old man comes for a pre-employment examination. He has no complaints and has no medical problems. He does not use tobacco, alcohol, or drugs and takes no medications. He has no occupational exposures and has lived his entire life in suburban Mississippi. His temperature is 36.7°C (98.0°F), blood pressure is 120/80 mmHg, pulse is 78/min, and respirations are 16/min. Examination shows no abnormalities. His chest x-ray shows a 1 .5 cm nodule in his right mid-lung field. Other labs are unremarkable. Which of the following is the most likely diagnosis?

105) A 30-year-old African American female presents with a two month history of shortness of breath and nonproductive cough. She has never had symptoms like these before. Her past medical history is significant for an episode of uveitis six months ago. She does not take any medications. She works as a secretary in a local office building. She does not use tobacco and drinks alcohol only on special occasions. She has no pets and has been monogamous with a single partner for the last three years. On physical examination, her temperature is 37.2°C (98.9°F), blood pressure is 126/76 mm Hg, pulse is 76/min and respirations are 16/min. Lung auscultation reveals patchy rales. The remainder of her examination is unremarkable. Chest x-ray shows diffuse interstitial infiltrates. Which of the following is the most likely cause of her shortness of breath?