P 465 to 494*Q 100...174*

.104) An obese 18-year-old woman is brought to the emergency department by her mother, who noted that she had been lethargic all day, and suffered a brief, seizure-like episode. One month earlier, the patient had been started on medication for type 2 DM. Lactic acid levels are normal. Which of the following medications most likely played a role in the patient’s current presentation?

.107) A 60-year-old woman recently diagnosed with type 2 DM complains of daily headaches and double vision that have gradually worsened over the previous month. An MRI shows a large pituitary adenoma. Which of the following is most likely being secreted by this tumor?

.110) A 62-year-old male comes to your office for a routine follow-up appointment. He has smoked one pack of cigarettes per day for the past 30 years and adamantly refuses to quit. He also drinks six to ten beers each weekend. His past medical history is significant for type 2 diabetes mellitus and hypertension. His last hemoglobinA1c was 8.3%. He is overweight with a current BMI of 27.5 kg/m2. While examining him, you notice a whitish patch over the anterior floor of his mouth. The lesion appears to have a granular texture and is not removed by scraping with a tongue depressor. Which of the following is most likely cause of his oral lesion?

.111) A 51 -year-old obese male presents to your office complaining of difficulty swallowing solids but not liquids. His medical history is significant for GERD. Six months ago he was diagnosed with Barrett's esophagus. He reports that three months after the diagnosis of Barrett's esophagus, his heartburn resolved. Barium swallow now reveals an area of symmetric, circumferential narrowing affecting the distal esophagus. Which of the following best explains this finding?

.112) A 23-year-old man comes to the physician because of a two-month history of loose stools, decreased appetite, and weight loss. He has no history of medical problems. He takes no medications. His temperature is 36.7°C (98°F), blood pressure is 120/76 mmHg, pulse is 90/min, and respirations are 16/min. Laboratory studies show: Hemoglobin 11.2 g/dL, MCV 80 fl, Leukocyte count 9,500/cmm, Segmented Neutrophils 65%, Bands 3%, Eosinophils 1%, Basophils 0%, Lymphocytes 25%, Monocytes 6%, Platelets 550,000/cmm, ESR 50 mm/hr, Serum sodium 145 mEq/L, Serum potassium 4.0 mEq/L. Test of the stool for occult blood is positive. Which of the following is the most likely type of diarrhea in this patient?

113) A 66-year-old man presents with a four week history of increasing back pain and severe constipation. He has no weakness or sensory symptoms in his legs. He takes acetaminophen for back pain, metoprolol for high blood pressure, and an over-the-counter fiber supplement for constipation. A screening colonoscopy 5-year ago was unremarkable. Rectal examination shows no abnormalities. Examination of the stool for occult blood is negative. His blood pressure is 135/80 mmHg and heart rate is 80/min. Abdominal examination shows no abnormalities. Laboratory studies show: Hb 9.5 g/dl, WBC 7,000/cmm, Platelets 300,000/cmm, BUN 28 mg/dl, Serum Creatinine 1.9 mg/dl, ESR 80/hr. Which of the following is the best explanation for this patient's constipation?

.114) A 12-year-old girl comes to the physician for chronic weight loss and fatigue. She has a history of bulky, floating, foul-smelling stools, flatulence and meteorism. She also has bone pain and easy bruising. Laboratory studies show anemia with serum iron: 25 mg/dl , ferritin: 25 mg/dl and serum total iron binding capacity 600 mg/dl (normal 300-360 mg/dL); PT is 16 sec. Physical examination shows loss of subcutaneous fat, pallor, hyperkeratosis and abdominal distention; bowel sounds are increased. Which of the following is most likely associated with this patient's condition?

.115) A 44-year-old male who has had an extensive small bowel resection for Crohn's disease has been on total parenteral nutrition for two years. He presented to the hospital with epigastric and right upper quadrant pain. He has been taking azathioprine. His vital signs are within normal limits. Physical examination shows mild right upper quadrant tenderness. An ultrasonogram shows several gallstones; an ultrasonogram performed two years ago did not demonstrate gall stones. Which of the following is the most likely cause of his gallstones?

.116) A 35-year-old Caucasian male presents to the emergency department with two episodes of bloody vomiting which occurred one-half hour ago. He has a history of migraines. For the past two days, he has been having severe headaches and has taken 20 tablets of aspirin without relief. He then resorted to heavy drinking and forgot about the pain. He drinks alcohol "occasionally" and has been smoking 1 pack of cigarettes daily for the past 18 years. Which of the following is the most likely explanation for this patient's hematemesis?

.117) A 29-year-old male with a 6-year history of HIV infection presents with chronic, severe diarrhea associated with malaise, nausea, anorexia and abdominal cramps. His last CD4 count was 80cells/mm3. A modified acid-fast stain of a stool specimen shows 4-6 mm oocysts. Which of the following is the most likely microorganism responsible for this condition?

.118) A 45-year-old Caucasian male presents with a 2-year history of progressive heartburn which is most severe while supine. Over-the-counter antacids have not relieved his symptoms. Endoscopy shows a hiatal hernia. The patient is reluctant to accept any treatment. Which of the following is he at risk for if his condition is left untreated?

.119) A 45-year-old male comes to the physician with a 6-month history of periodic abdominal pain. He tried several over-the-counter medications including H2 blockers and proton pump inhibitors with moderate success. Workup, including an upper GI series and endoscopy, showed multiple duodenal ulcers and a single jejunal ulcer. Test of the stool for occult blood is positive. Test of the stool for fat is positive. Which of the following is the best explanation for this patient's impaired fat absorption?

.120) A 58-year-old man presents with a one-year history of diarrhea. The stools are watery and accompanied by abdominal cramps. He denies any fever, blood per rectum, or foul-smelling stools. He has also experienced frequent episodes of dizziness, flushing, wheezing, and a feeling of warmth. He has taken herbal medicines, which failed to relieve his symptoms. He is depressed about his illness, and feels hopeless about diagnosis and treatment. He appears ill. Auscultation of the chest shows a 2/6 systolic murmur over the left lower sternal border. Abdominal examination shows hepatomegaly 3cm below the right costal margin, mild shifting dullness, and no abdominal tenderness. Laboratory studies show: Hb 13.0gm/dl, MCV 90fl, WBC 6,100/cmm, Platelets 210,000/cmm, AST101 U/L, ALT 99 U/L, Alkaline phosphatase 400 mg/dl. This patient is at risk of developing a deficiency of which vitamin or mineral?

.121) A 65-year-old Caucasian male presents to your office with a several month history of difficulty swallowing. He has noticed a right-sided neck mass which increases in size while drinking fluids. His past medical history is significant for hypertension, gastroesophageal reflux disease, and osteoarthritis of his right knee. His current medications include hydrochlorothiazide, ranitidine, and occasional naproxene. You order a barium examination of the esophagus to visualize the abnormality. Which of the following is the most important pathogenetic factor in the development of this patient's problem?

.122) A 20-year-old male university student presents with a one-month history of 4 to 6 loose watery bowel movements per day with occasional tenesmus, urgency, and abdominal cramps. He also describes a two-week history of intermittent bright red blood per rectum. His appetite and energy levels are excellent and his weight is stable. He is otherwise healthy and takes no medications. His family history is unremarkable. He has not recently used antibiotics nor has he traveled outside the country. He does not use tobacco, alcohol or drugs. Sigmoidoscopy demonstrates mild erythema and rectal biopsy confirms acute mucosal inflammation. Which of the following is a potential complication of this condition requiring regular surveillance?

.123) A 46-year -old alcoholic man comes to the emergency department because of several episodes of vomiting. The last episode of emesis contained blood. Five hours ago, he had a fatty meal and several alcoholic drinks. Two days ago, he had an upper GI tract endoscopy and abdominal ultrasound for the evaluation of dyspepsia. The endoscopy was unremarkable, and the ultrasound showed a hyperechogenic enlarged liver and stones in the gallbladder. His temperature is 36.6°C (97.9°F), blood pressure is 120/70 mm Hg, pulse is 95/min, and respirations are 15/min. Laboratory studies show: Hb 12.8 g/dl, WBC 5,400/cmm, BUN 26 mg/dl, Creatinine 1.1 mg/dl, AST 100 U/L, ALT 45 U/L, Bilirubin 0.7 mg/dl. Nasogastric suction shows normal stomach contents mixed with bright red blood. The rectal examination shows no melena. Which of the following is the most likely explanation for this patient's bloody vomiting?

.124) A 53-year-old woman presents to your office with right-sided abdominal pain that started two days ago. She describes the pain as constant and burning in nature. There is no associated nausea, vomiting or diarrhea. The patient reports taking over-the-counter antacids and ibuprofen, which brought no relief. Her medical history is significant for breast cancer diagnosed one year ago, for which she underwent a modified radical mastectomy and is receiving chemotherapy, the last course of which was completed two months ago. On physical examination, her temperature is 36.7°C (98°F), blood pressure is 120/70 mm Hg, pulse is 80/min, and respirations are 16/min. Her lung fields are clear to auscultation and her abdomen is soft and non-distended. The liver span is 10 cm and the spleen is not palpable. Lightly touching the skin to the right of the umbilicus elicits intense pain. In one week the patient is most likely to develop:

.125) A 20-year-old Caucasian male presents with lower abdominal pain for the past few hours. The pain first started around the umbilicus, but then shifted to the right lower abdominal area. He has had one episode of vomiting. Physical examination shows tenderness at McBurney's point. CT scan of the abdomen confirms the diagnosis of acute appendicitis. Which of the following explains the pathophysiology of the shifting of pain from the peri-umbilical area to the right lower quadrant in acute appendicitis?

.126) A husband and wife present to the ED with 1 day of subjective fever, vomiting, watery diarrhea, and abdominal cramps. They were at a restaurant a day before for dinner and both ate the seafood special, which consisted of raw shellfish. In the ED, they are both tachycardic with temperatures of 99.8°F and 99.6°F for him and her, respectively. Which of the following is responsible for the majority of acute episodes of diarrhea?

.127) A 21-year-old woman presents to the ED complaining of diarrhea, abdominal cramps, fever, anorexia, and weight loss for 3 days. Her BP is 127/75 mm Hg, HR is 91 beats per minute, and temperature is 100.8°F. Her abdomen is soft and nontender without rebound or guarding. WBC is 9200/μL, β-hCG is negative, urinalysis is unremarkable, and stool is guaiac positive. She tells you that she has had this similar presentation four times over the past 2 months. Which of the following extraintestinal manifestations is associated with Crohn disease but not ulcerative colitis?

.128) A 67-year-old woman is currently postoperative day 8 after an emergent laparoscopic cholecystectomy for acute cholecystitis. On postoperative day 2 she spiked a temperature of 40°C (101.4°F) and began to complain of some shortness of breath. X-ray of the chest revealed right lower lobe pneumonia, and the patient was started on clindamycin. Today she is experiencing multiple episodes of foul-smelling, watery diarrhea that is green tinged but non-bloody. She also complains of lower abdominal cramping. Her temperature is 37.8°C (100°F), pulse is 90/min, respiratory rate is 15/min, and blood pressure is 110/70 mm Hg. Which of the following is the most likely explanation for these findings?

.129) A 73-year-old woman presents to the emergency room with black tarry stools and symptoms of presyncope when standing up. Digital rectal examination confirms the presence of melena. She recently started using ibuprofen for hip discomfort. Upper endoscopy confirms the diagnosis of a gastric ulcer. Which of the following is the most likely explanation for the gastric ulcer?

.132) A 78-year-old man with a history of atherosclerotic heart disease and congestive heart failure presents with increasing abdominal pain. The pain began suddenly a day ago and has progressively worsened since then. He denies nausea, vomiting, and diarrhea, but states that he had black tarry stool this morning. He denies any history of prior episodes of similar pain. Vitals are BP 120/65 mm Hg, HR 105 beats per minute, and temperature 99°F. The patient is at high risk for which of the following conditions?

.134) A 72-year-old woman notices progressive dysphagia to solids and liquids. There is no history of alcohol or tobacco use, and the patient takes no medications. She denies heartburn, but occasionally notices the regurgitation of undigested food from meals eaten several hours before. Her barium swallow is shown. Which of the following is the cause of this condition?

.135) A 33-year-old woman develops mild epigastric abdominal pain with nausea and vomiting of 2 days duration. Her abdomen is tender on palpation in the epigastric region, and the remaining examination is normal. Her white count is 13,000/mL, and amylase is 300 U/L (25–125 U/L). Which of the following is the most common predisposing factor for this disorder?

.136) A 54-year-old man complains of burning epigastric pain that usually improves after a meal, and is occasionally relieved with antacids. On examination, he appears well and besides some epigastric tenderness on palpation, the rest of the examination is normal. Upper endoscopy confirms a duodenal ulcer. Which of the following statements concerning PUD is most likely correct?

.137) A 60-year-old man with no past medical history undergoes upper endoscopy and biopsy for an upset stomach that is worsened by eating. He is found to have inflammation predominantly in the antrum of the stomach. Which of the following is the most likely etiology of this condition?

.138) A 23-year-old woman presents to the ED complaining of pain with urination. She has no other complaints. Her symptoms started 3 week ago. During this time, she has been to the clinic twice, with negative urine cultures each time. Her condition has not improved with antibiotic therapy with sulfonamides or quinolones. Physical examination is normal. Wet mount showed epithelial cells. Which of the following organisms is most likely responsible for the patient’s symptoms?

.141) A term boy with Apgar scores of 9 and 9 at 1 and 5 minutes has failed to pass meconium at 72 hours. He has had no episodes of emesis, and his abdomen is only mildly distended to palpation. The patient’s mother reports that her older son had the same problem at birth. A plain radiograph of the abdomen shows a small bowel obstruction with numerous air-filled loops of bowel. The patient is treated with a diatrizoate meglumine (Gastrografin) enema, with good results. Which of the following is the most likely mechanism for this infant’s acute intestinal problem?

.143) A 43-year-old man feels vaguely unwell. Physical examination is unremarkable except for evidence of scleral icterus. The skin appears normal. Which of the following is the most likely explanation for why early jaundice is visible in the eyes but not the skin?

.144) A 56-year-old woman becomes the chief financial officer of a large company and, several months thereafter, develops upper abdominal pain that she ascribes to stress. She takes an over-the-counter antacid with temporary benefit. She uses no other medications. One night she awakens with nausea and vomits a large volume of coffee grounds-like material; she becomes weak and diaphoretic. Upon hospitalization, she is found to have an actively bleeding duodenal ulcer. Which of the following statements is true?

.145) A 50-year-old man wants to talk to you about something, "absolutely confidential". After you assure him, he admits, "He is unable to get an erection and just can't have sex." He wants to figure it out quickly because "he simply can't live like this." He has never been diagnosed with diabetes and denies other complaints. He has a 2 pack/day history of smoking for 30 years. On examination, his BP: 158/90mm of Hg; Temperature: 37.1°C (98.8°F); RR 14/min; PR 82/min. There is upper body obesity, rounded face, increased fat around the neck, and thinning of arms and legs. You find his skin to be bruised, fragile and thin. Laboratory reveals the following results. Serum: Glucose 186 mg/dl, Sodium 142 mEq/L, Potassium 2.5 mEq/L, Bicarbonate 38 mEq/L. Chest X ray shows a large mass in left bronchus. What is the most likely cause of patient's condition?

.146) A 66-year old female has been your patient for the last 8 years. She was diagnosed with colorectal carcinoma 2 years ago, and eventually underwent an endoscopic resection. Since then, she has been healthy, and has been coming to the office regularly for follow-up visits. She is very grateful, and has stated many times that she owes her life to you. You are currently a co-investigator of a retrospective observational study of patients with colon cancer, and you believe that including her medical information will be extremely beneficial. What course of action must you take so that you can include this patient's data in your study?

.147) A 65-year-old woman comes to the office for a health maintenance visit. She has been your patient for the last 15 years. When you ask how she has been, she replies with, "Well, I'm very health-conscious now. I read all the health magazines regularly, and exercise for 30 minutes daily. I eat a lot of garlic to control my cholesterol, and drink cranberry juice to keep my kidneys strong. I don't smoke, but I drink alcohol during social events. I've been compliant with regular screening colonoscopies, mammograms, and pap smears. Doc, since my mother died from ovarian cancer, do you think I can have an abdominal ultrasound every 6 months, plus any additional necessary tests, so that any cancer can be detected early?" What is the best response to this patient's concerns?

.148) A 22-year-old African-American man presents to the ER with fever, jaundice, abdominal pain, and 482 dark urine. His heart rate is 100/min and blood pressure is 100/60 mmHg. Peripheral blood smear reveals bite cells and red blood cell inclusions seen after crystal violet staining. The patient most likely suffers from which of the following conditions?

.150) A 43-year-old man presents to your office with low energy and increased fatigability. He also complains of daytime sleepiness and occasional headaches. He drinks two to three glasses of wine daily but does not smoke. He sleeps in a separate room from his wife because she finds his constant snoring annoying. On physical examination, his blood pressure is 160/100 mmHg and his heart rate is 80/min. His BMI is 31.5 kg/m2. His abdomen is soft and non-tender. The liver span is 10 cm and the spleen is not palpable. Laboratory findings are: Hematocrit 60%, WBC count 9,000/mm3, Platelets 190,000/mm3. Which of the following is most likely responsible for this patient's increased hematocrit?

.151) A 6-year-old African-American child is brought in by his father for complaints of easy fatigability and pallor. These symptoms occurred after the son was treated with "some medication" for a recent diarrhea. Physical examination is normal except for pallor and multiple petechiae. Laboratory values are as follows: Hb 8.0 g/dL, WBC 12,000/cmm, Platelets 50,000/cmm, Blood glucose 118 mg/dL, Serum Na 135 mEq/L, Serum K 5.3 mEq/L, Chloride 110 mEq/L, Bicarbonate 18 mEq/L, BUN 38 mg/dL, Serum creatinine 2.5 mg/dL, Total bilirubin 3 mg/dL, Direct bilirubin 0.5 mg/dL, PT 12 seconds, APTT 30 seconds, LDH 900 IU/L, Reticulocyte count 6%. A peripheral blood smear reveals giant platelets and multiple schistocytes. What is the most likely underlying pathophysiology for this boy's pallor?

.153) A 79-year-old woman presents to your office complaining of an intermittent skin rash over the last several months. She denies fever, headache, and recent weight loss. Her past medical history is significant for diet-controlled diabetes and right knee osteoarthritis treated with acetaminophen. Physical examination reveals several dark purple ecchymotic areas over the dorsum of both arms. Her abdomen is soft and non-tender. The liver span is 8 cm and the spleen is not palpable. Laboratory studies reveal: Hematocrit 47%, WBC count 5,800/mm3, Platelet count 220,000/mm3, Serum creatinine 0.8 mg/dL\, Fibrinogen 350 mg/dL, Prothrombin time 10 sec, INR 1.0, Partial thromboplastin time 25 sec. Which of the following is the most likely cause of this patient's complaint?

.154) A 42-year-old woman is evaluated for chronic abdominal pain and fatigue. Her pain is epigastric, crampy, and sometimes awakens her from sleep. She denies any recent weight loss, nausea, or vomiting. Her diet consists mainly of fruits and vegetables. She also complains of a "strange appetite" for paper and ice that she has never had before. Upper gastrointestinal endoscopy reveals an ulcer located on the anterior wall of the duodenal bulb. Her unusual appetite is most directly related to:

.155) A 22-year-old female presents to the emergency room with a nosebleed. A quick review of her records reveals that she presented with the same problem yesterday, at which time the bleeding was stopped with prolonged local pressure. On review of systems, the patient also reports easy bruising for the past several months. On physical examination, her heart and lungs appear normal. The liver span is 8 cm and the spleen is not palpable. There are scattered ecchymoses over her arms and legs. Laboratory findings include the following: Hematocrit 45%, Platelet count 9,000/mm3, Leukocyte count 5,500/mm3, Neutrophils 56%, Eosinophils 1%, Lymphocytes 33%, Monocytes 10%, Fibrinogen 250 mg/dL, Prothrombin time 13 sec. Which of the following is the most likely cause of this patient's condition?

.156) A 66-year-old female comes for removal of a lipoma from her elbow. She wants the swelling out because it looks ugly when she wears sleeveless tops. Her only complaints are general malaise and fatigue for the past 8 months, which she attributes to her "being alone all the time." Her vital signs are within normal limits. Physical examination reveals mild pallor and both cervical and supraclavicular lymphadenopathy. Her preoperative blood count reveals the following: Hemoglobin 10.0 g/dL, Hematocrit 32%, Platelets 126,000/cmm, WBC 31,600/cmm. Leukocyte distribution: Segmented neutrophils 18%, Lymphocytes 77%, Bands 4%, Monocytes 1%. The pathologist reports the presence of "leukocytes that have undergone partial breakdown during preparation of a stained smear or tissue section, because of their greater fragility." Lymph node biopsy confirms the diagnosis. What is the correct statement about the above patient?

.157) A 17-year-old male presents to clinic for routine check-up. He is a long distance runner and has beenachieving outstanding results recently. He is very proud of his athletic achievements, remarking that his effort "pays off." He does not smoke or consume alcohol. His family history is significant for diabetes mellitus in his mother and skin cancer in his father. Chest examination is normal. His liver span is 8 cm and his spleen is not palpable. His current laboratory findings include: Hematocrit 59%, WBC count 7,500/mm3, Platelet count 170,000/mm3, ESR 15 mm/hr. Which of the following is the most likely explanation for the high hematocrit in this patient?

.158) A 65-year-old Caucasian male had undergone cardiac catheterization followed by aortic valve replacement for severe aortic stenosis and coronary artery bypass grafting for three-vessel disease. His postoperative course was complicated by atrial fibrillation and a urinary tract infection. His other medical problems include hypertension, diabetes, and hypercholesterolemia. He is also receiving heparin, ciprofloxacin, and amiodarone. On postoperative day five, he developed prolonged bleeding from the venipuncture site. His labs show: Hb 11.5 g/dL, MCV88 fl, Platelet count 50,000/cmm, Leukocyte count 7,500/cmm, Segmented neutrophils 68%, Bands 1%, Eosinophils 1%, Lymphocytes 24%, Monocytes 6%, Prothrombin time 12 sec (INR=1.0), Partial thromboplastin time 65 sec. His preoperative labs were unremarkable. What is the most likely cause of these findings in this patient?

.159) A 62-year-old woman presents complaining of recurrent cough productive of yellow sputum. She was seen several weeks ago for similar complaints and was effectively treated with a course of azithromycin. Today she expresses frustration that she seems to keep getting sick with the same infection. On review of systems, the patient also reports recent-onset back pain for which she has been taking acetaminophen. Her past medical history is otherwise insignificant. She has never smoked cigarettes, and drinks alcohol only on rare social occasions. Physical examination reveals conjunctival pallor, a few scattered rales in the lungs bilaterally, and tenderness over the lumbar vertebrae. Laboratory analyses reveal: Hemoglobin 8.4 g/dL, Leukocyte count 5,500/mm3, Blood urea nitrogen 34 mg/dL, Creatinine 2.0 mg/dL, Calcium 10.9 mg/dL, Albumin 3.8 g/dL, Total protein 9.5 g/dL. This patient is at increased risk for recurrent infections because of which of the following abnormalities?

.160) A 47-year-old man presents to your office complaining of occasional daytime headaches, dizziness and nausea. He has no significant past medical history. He works as a traffic controller in an underground parking lot. He does not smoke cigarettes, and consumes alcohol only on weekends. He is sexually active in a monogamous relationship with his wife and uses condoms for contraception. His cardiac exam is unremarkable. His abdomen is soft and non-tender. The liver span is 8 cm and the spleen is not palpable. Laboratory findings are: Hematocrit 59%, WBC count 7,000/mm3, Platelets 200,000/mm3. Which of the following is most likely responsible for this patient's increased hematocrit?

.162) A 25-year-old African American woman presents with a photo distributed skin rash and arthralgias. She is found to have low-range proteinuria and abnormal urinary sediment. Renal biopsy findings are consistent with focal proliferative glomerulonephritis. Her complete blood count shows: Erythrocyte count 3.2 mln/mm3, Platelets 60,000/mm3, Leukocyte count 2,500/mm3. Which of the following is the most likely cause of these hematologic findings?

.163) A 45-year-old Asian man presents to your office complaining of easy fatigability. He denies abdominal pain, distention, nausea, vomiting, or significant weight loss. His past medical history includes a gastrectomy for a non-healing gastric ulcer. He is not currently taking any medications. He quit smoking several years ago and does not use alcohol or illicit drugs. His vital signs are within normal limits. Physical examination reveals a shiny tongue and pale palmar creases. No lymphadenopathy, hepatomegaly, or splenomegaly is present. His blood hemoglobin level is 7.5 mg/dL and W8C count is 3,800/mm3. Stool tests for occult blood are repeatedly negative. This patient's condition involves which of the following pathophysiologic mechanisms?

.164) A 23-year-old African American man is treated with an antibiotic for an uncomplicated urinary tract infection. Several days later, he presents to your office saying that his initial symptoms have improved but his urine now appears dark. He has no significant past medical history and does not use tobacco, alcohol, or illicit drugs. His temperature is 36.8°C (98.2°F), pulse is 88/min, respirations are 14/min, and blood pressure is 130/76 mmHg. Physical examination is within normal limits. The urine sample stains positive with Prussian blue and the sediment microscopy is unrevealing. What is the mechanism behind the cell damage responsible for this patient's current complaint?

.165) A 6-year-old Caucasian boy is hospitalized for acute sinusitis that was accompanied with intensive nasal bleeding. Past medical history is significant for recurrent pulmonary infections and several hospitalizations for parenteral antibiotic therapy. The sweat chloride test is positive. The blood tests reveal a prothrombin time (PT) of 20 seconds. Which of the following coagulation factors is most likely to be deficient in this patient?

.166) A 27-year-old man presents to the emergency department with unremitting nose bleeding. He reports having a similar bleeding episode one year ago that was stopped in the ER. He works as a computer programmer and has a sedentary lifestyle. He drinks alcohol on social occasions but does not smoke or use illicit substances. On physical examination, there are several ruby-colored papules on his lips that blanch partially with pressure. Digital clubbing is also present. His abdomen is soft and non-tender. The liver span is 8 cm and the spleen is not palpable. Laboratory findings are: Hematocrit 60%, WBC count 8,000/mm3, Platelets 180,000/mm3. Which of the following is most likely responsible for this patient's increased hematocrit?

.167) A 14-year-old boy is brought by his mother because she noticed a change in his voice. He has been having frequent nosebleeds for the last month, and feels that his "left nose" is always congested. There is no history of trauma. He admits to using marijuana, in the absence of his mother. He is otherwise well, and does not take any medications. He actively participates in the school basketball tournaments. Physical examination reveals an intact nasal septum with a visible mass at the back of the left nostril. CT scan reveals an erosion of the adjacent bone. What is the most likely reason of this patient's nosebleeds?

.168) A 34-year-old male who recently emigrated from Asia comes to the clinic and complains of a two-month history of exertional shortness of breath and easy fatigability. He has been taking isoniazid and rifampin for his tuberculosis, which was diagnosed four months ago. Due to his religious beliefs, he completely turned into a vegetarian for the last year. Physical examination reveals severe pallor. Peripheral smear shows macrocytosis with hypersegmented polymorphonuclear neutrophils. His WBC and platelet counts are within normal limits. This patient's most likely problem is due to which of the following?

.169) A 72-year-old woman complains of fatigue, dyspepsia, and shortness of breath. Her daughter tells you that her mother also has some slight memory loss and occasionally complains of numbness in her legs. The laboratory tests you ordered show a hemoglobin of 10.2 g/dL and an MCV of 110. The most likely cause is:

.171) A 55-year-old Asian man with mitral stenosis secondary to rheumatic heart disease undergoes dental surgery for caries. Postoperatively, he does well and is discharged home. Two weeks later, he presents with fever, chills, fatigue, and feels "sick." Four out of four blood culture bottles are positive for gram-positive cocci. An echocardiogram is performed and shows mitral valve vegetations. Which of the following is the most likely causative organism of this patient's condition?

.172) A 16-year-old Asian boy presents with a two-day history of fever, malaise, and painful enlargement of his parotid glands. He has no significant past medical history. He was born in India, and has not received any childhood vaccinations. He recently returned from a one-week vacation in India. His vital signs are stable, except for a mild fever. Examination shows bilateral parotid enlargement. The rest of the examination is unremarkable. Which of the following organs is most likely to be affected by this patient's illness?