1. A study is conducted to assess whether there is a relationship between daily fish oil intake and renal disease progression in patients with IgA nephropathy. A total of 250 patients with biopsy-proven IgA nephropathy are enrolled: 125 patients are assigned to receive 4 g offish oil concentrate daily, and 125 patients are assigned to receive a placebo. The treating physicians are blinded to which patients are receiving fish oil and which are receiving placebo. Renal function in these patients is assessed on a semiannual basis for the next 10 years, and the number of patients who develop end-stage renal disease in each group is noted. Which of the following is the strongest rationale for randomization?

O A) Decreases the risk of bias O B) Decreases the risk of a Type II error O C) Decreases the sample size required to obtain significant results O D) Ensures that all patients have valid disease O E) Increases the power of the study

2. A 23-year-old man in the emergency department has apnea and pinpoint pupils. Needle tracks are present on his arms. Activation of which of the following opioid receptors in the central nervous system is most likely to be responsible for the apnea?

O A ) 5 O B) K O C ) P O D ) a

3. A 60-year-old man with metastatic prostate cancer has difficulty speaking and swallowing. He has weakness of elevation of the right side of the palate and weakness and atrophy of the right sternocleidomastoid and trapezius muscles. These findings are most likely to be caused by a lesion in which of the following structures?

O A) Foramen ovale O B) Foramen rotundum O C) Hypoglossal canal O D) Jugular foramen O E) Stylomastoid foramen

4. A 65-year-old woman is hospitalized for treatment of lobar pneumonia. Parenteral cephalosporins produce initial improvement in symptoms. However, on the seventh hospital day, she develops hypotension and her temperature increases to 39.4°C (103°F). Blood cultures are obtained, and Klebsiella pneumoniae is isolated from multiple specimens. Results of in vitro susceptibility studies for several antimicrobials using the agar disk diffusion (Kirby-Bauer) technique are shown:

Which of the following is the most likely mechanism of the antimicrobial resistance observed for this isolate?

O A) Active efflux of antibiotic from bacterial cells O B) Alteration in penicillin-binding proteins in peptidoglycanO C) Changes in outer membrane proteins preventing entry of antibiotic into the bacterial cell O D) Methylation of bacterial ribosomes O E) Production of extended-spectrum (3-lactamase

AntimicrobialAmpicillinCefotetan

CeftriaxoneCeftazidimeCefpodoximePiperacillin

resistantsusceptibleresistantresistantresistantresistant

susceptiblesusceptiblesusceptible

Piperacillin-tazobactamTicarcillin-clavulanate

Imipenem

5. A normal woman is a carrier of an X-linked recessive disorder that is lethal in utero (spontaneously aborted). Which of the following' the expected ratio of her viable female to male children?

Lab Values F

O A ) 1:1 O B) 1:2 O C) 2:1 O D) 2:3 O E) 3:2

O A) Inferior mesenteric O B) Inferior phrenic O C) Left gastroepiploic O D) Splenic O E) Superior mesenteric

7. A 25-year-old man is brought to the emergency department because of a 2-week history of fever, chills, and productive cough; he has had a 4.5-kg (10-lb) weight loss during this period. He has a 3-year history of multiple episodes of sinusitis, bronchitis, and pneumonia, for which he has received treatment with various antibiotics. He is married and has one adopted child; his wife has been unable to conceive. He is 173 cm (5 ft 8 in) tall and weighs 50 kg (110 lb); BMI is 17 kg/m2. His temperature is38.9°C (102°F), pulse is 110/min, respirations are 30/min, and blood pressure is 120/70 mm Hg. Crackles are heard over the right hemithorax, and there is dullness to percussion at the right base. Cardiac examination shows heart sounds that are loudest on the right. A 12-cm mass is palpable in the left upper quadrant of the abdomen. Which of the following is the most likely underlying cause of this patient's condition?

O A) Cell death of the ciliated cellsO B) Cell death of the pulmonary alveolar macrophagesO C) Decreased serum IgM concentrationO D) Dysfunction of the pulmonary alveolar macrophagesO E) Dyskinesia of the ciliaO F) Increased serum IgE concentration

O A) Cholecystokinin O B) Gastrin O C) GlucagonO D) Glucose-dependent insulinotropic peptide O E) Motilin O F) SecretinO G) Vasoactive intestinal polypeptide

9. A 21-year-old woman is brought to the emergency department 2 hours after the onset of fever, chills, severe headache, and confusion. Her temperature is 39°C (102.2°F), respirations are 16/min, and blood pressure is 100/60 mm Hg. Physical examination shows numerous petechial lesions over the upper and lower extremities. There is resistance to neck flexion. Analysis of cerebrospinal fluid shows numerous leukocytes and gram-negative diplococci. She had a similar episode 3 years ago caused by infection with the same organism. This patient most likely has a deficiency of which of the following?

O A ) C1 O B) C3 O C ) C4 O D ) C8O E) Mannose-binding lectin O F) Properdin

A 59-year-old woman dies of breast cancer. At autopsy, examination shows an outpouching from the apex of the urinary bladder. This pouch is continuous with a fibrous cord running in the direction of the umbilicus in the anterior abdominal wall. The pouch represents a remnant of which of the following embryonic structures?

11. A 52-year-old woman has had slowly progressive weakness and weight loss of 9 kg (20 lb) for 4 months. She has never traveled outside of the USA. Her blood pressure is 82/50 mm Hg. Her skin shows diffuse hyperpigmentation. Plasma concentration of ACTH is markedly increased, and the serum concentration of cortisol is decreased. CT scans of the chest and abdomen disclose no mass lesions. Which of the following is the most likely etiology of this patient's disease?

O A) Autoimmune O B) Congenital O C) Infectious O D) Metabolic O E) Neoplastic

12. During a study of intravenous urinary catheters, an investigator sterilizes a plastic catheter by incubation in alcohol. This compound acts by disrupting which of the following structures?

O A) Cell wall O B) DNA O C) Membrane O D) Protein O E) RNA

13. A 25-year-old woman is evaluated for infertility. She has a history of pelvic inflammatory disease due to Neisseria gonorrhoeae infections. Based on history alone, the most likely cause of this patient's infertility is the effect of her infection on which of the following structures?

O A) Cervical glands O B) Endometrium O C) Fallopian tube O D) Myometrium O E) Ovary

14. A 60-year-old woman develops a painful unilateral vesicular skin eruption along the T-2 and T-3 dermatome distribution after; vacation at the beach. Which of the following is most likely associated with the rash?

O A) Allergic reaction to p-aminobenzoic acid O B) A childhood illness O C) Coxsackie A1 virus infection O D) Photosensitivity drug reaction

15. A61-year-old man is brought to the emergency department because of a 1-hour history of severe chest and abdominal pain. He first noticed a sharp pain in his back 3 hours ago while stacking firewood in his backyard. Since that time, the pain has increased in intensity and generalized in distribution. He appears weak and diaphoretic. His temperature is 37°C (98.6°F), pulse is 100/min, respirations are 40/min, and blood pressure is 198/110 mm Hg. Breath sounds are mildly decreased in the left lung base. A faint

15. A61-year-old man is brought to the emergency department because of a 1-hour history of severe chest and abdominal pain. He first noticed a sharp pain in his back 3 hours ago while stacking firewood in his backyard. Since that time, the pain has increased in intensity and generalized in distribution. He appears weak and diaphoretic. His temperature is 37°C (98.6°F), pulse is 100/min, respirations are 40/min, and blood pressure is 198/110 mm Hg. Breath sounds are mildly decreased in the left lung base. A faint diastolic murmur is heard in the third left intercostal space. Abdominal examination shows guarding but no masses or organomegaly. CT scans of the chest and abdomen with contrast are shown; a Stanford type A aortic dissection is indicated by the arrows. This patient is at greatest risk for which of the following?

O A) Aortic stenosis O B) Cardiac tamponade O C) Mitral insufficiency O D) Pulmonary embolism O E) Pulmonary hypertension

16. A 31-year-old man receives medication to reverse the effects of a neuromuscular-blocking drug. Two minutes later, he has decrease in heart rate to 28/min. Which of the following drugs or combination of drugs was most likely used to reverse the neuromuscular blockade in this patient?

O A) Anticholinesterase drug onlyO B) Anticholinesterase and cholinesterase reactivator drugs in combination O C) Anticholinesterase and muscarinic antagonist drugs in combination O D) Cholinesterase reactivator drug only O E) Direct muscarinic agonist drug only

Lab Values F

17. An investigator is conducting a study of immune responses to inoculation with tumor cells in two groups of mice. Group 1 is inoculated with tumor cells with increased expression of interleukin-2 (IL-2) due to transfection with the IL-2 gene. Group 2 is inoculated with nontransfected tumor cells. It is observed that the immune response in Group 1 is enhanced compared to the immune response in Group 2. This difference in immune response is best explained by enhanced proliferation of which of the following cell types in Group

O A) Dendritic cells O B) Macrophages O C) Neutrophils O D) Plasma cells O E) T lymphocytes

18. A 65-year-old man comes to the physician because of increasingly severe pain in his right leg during the past month. The pain occurs after walking two blocks and resolves with rest. He has had no numbness, tingling, weakness, or swelling. He has type 2 diabetes mellitus, hypertension, and hypercholesterolemia. Current medications include metformin, hydrochlorothiazide, and pravastatin. He has smoked 1 'A packs of cigarettes daily for 40 years. His pulse is 80/min, and blood pressure is 140/90 mm Hg. Physical examination shows no tenderness or edema of the lower extremities. The dorsal pedal and posterior tibial pulses are 1+ on the right and 2+ on the left. Patellar and Achilles deep tendon reflexes are 1 + bilaterally. Which of the following is the most likely cause of this patient's condition?

O A) Deep venous thrombosis O B) Diabetic neuropathy O C) Osteoarthritis O D) Peripheral vascular disease O E) Spinal stenosis

19. A 55-year-old man is brought to the emergency department 1 hour after he collapsed at home. On arrival, his pulse is 120/min, respirations are 16/min, and blood pressure is 80/45 mm Hg. Physical examination shows pale conjunctivae. His hemoglobin concentration is 8 g/dL, hematocrit is 24%, and platelet count is 240,000/mm3. Endoscopy shows a bleeding duodenal ulcer, which!_ surgically repaired. He receives 4 units of packed red blood cells. Two days later, laboratory studies show:

Hemoglobin 10 g/dLHematocrit 30%Serum

Urea nitrogen 70 mg/dLCreatinine 3 mg/dL

Volume Total protein Sodium OsmolalityFractional excretion of sodium Sediment

100 mL/24 h 100 mg/24 h 50 mEq/L300 mOsmol/kg H20 2.5%granular casts

Histologic examination of a renal biopsy specimen is most likely to show which of the following findings?

O A) Lymphocytic infiltrate in interstitium and tubules O B) Necrosis of epithelial cells in proximal convoluted tubules O C) Papillary necrosis with neutrophilic infiltrates O D) Renal infarction with a wedge-shaped zone of coagulation necrosis O E) No significant pathology

20. A 32-year-old man comes to the physician because of a chronic skin lesion that developed shortly before he was discharged from active military duty in Iraq 6 weeks ago. The lesion began as a painless red papule on his right arm that gradually became nodular: it now is growing larger. Physical examination shows a 4 x 5-cm crusting lesion with an irregular but sharp border on the right upper extremity. A Giemsa stain of a biopsy specimen shows multiple 1.3-to 3-viM inclusions within histiocytes. Which of the following is the most likely causal organism?

O A) Histoplasma capsulatum O B) Leishmania major O C) Plasmodium vivax O D) Strongyloides stercoralis O E) Toxoplasma gondii

21. A 14-year-old girl is admitted to the hospital after sustaining injuries in a house fire. Her temperature is 37.2°C (99°F), pulse ism Hg. Physical examination shows second-degree burns ove

138 mEq/L 4 mEq/L 90 mg/dL 3.5 mg/dL

A decrease in which of the following is the most likely explanation for this patient's laboratory findings?

O A) Collecting duct free water reabsorption O B) Distal tubule potassium secretion O C) Distal tubule sodium reabsorption O D) Glomerular filtration O E) Proximal tubule sodium reabsorption

Lab Values F

22. A 60-year-old man is brought to the emergency department because of a 2-day history of progressively uncontrollable, involuntary flinging movements of his right arm and leg. He has a 20-year history of hypertension treated with enalapril. Neurologic examination shows continuous circular and flapping motions of the right lower extremity and jerky movements of the right upper extremity. He has a tendency to fall to the right. The most likely cause of his condition is a lacunar infarction in which of the following locations?

O A) Anterior limb of the left internal capsule O B) Left subthalamic nucleus O C) Posterior limb of the left internal capsule O D) Posterior limb of the right internal capsule O E) Right subthalamic nucleus

23. A 23-year-old woman with schizophrenia is brought to the emergency department from an inpatient psychiatric facility 30 minutes after she accidentally burned her leg with boiling water while cooking. Physical examination shows an 8-cm area of erythema and blistering on the anterior section of the right thigh. The patient refuses treatment. She says, "I know I have a thought problem I take medication for, but I never know who to trust. I want to wait until my parents get here. I know that my leg could get infected if I wait too long, but I don't think it is going to kill me if I wait a few hours." Which of the following initial actions by the physician is most appropriate at this time?

O A) Do not proceed with treatment and determine if her parents are on their way O B) Do not proceed with treatment until a court order can be obtained ordering therapy O C) Do not proceed with treatment until a psychiatric evaluation is completed O D) Proceed with treatment because she admits that she has a psychiatric disorder O E) Proceed with treatment because she has been placed in a psychiatric facility O F) Proceed with treatment because she is showing signs of paranoia, which proves her to be incompetent

24. A 42-year-old man with hypertension, gout, and type 1 diabetes mellitus undergoes renal transplantation. His immunosuppressive regimen includes azathioprine, prednisone, and cyclosporine. The dose of azathioprine would have to be adjusted if he is taking which of the following drugs?

O A) Allopurinol O B) Atenolol O C) Diltiazem O D) Glyburide O E) Urecholine

25. A 6-year-old boy is brought to the physician because of a 2-week history of increasingly severe pain in his left shoulder. The onset c pain was sudden. His temperature is 38.9°C (102°F). Physical examination shows erythema, tenderness, and warmth over the left shoulder and decreased range of motion of the left upper extremity. Laboratory studies show:

An x-ray of the left shoulder shows a lytic lesion of the proximal humerus adjacent to the metaphysis. Which of the following is the i likely causal organism?

O A) Enterococcus faecalis O B) Escherichia coli O C) Mycobacterium tuberculosis O D) Staphylococcus aureus O E) Streptococcus pneumoniae O F) Treponema pallidum

Leukocyte count Segmented neutrophils Lymphocytes Monocytes

Erythrocyte sedimentation rate

15,000/mm370%20%10%63 mm/h

26. A 26-year-old woman comes to the physician to be fitted for a new diaphragm. She had an elective abortion for an unplanned and unwanted pregnancy 2 months ago. She and her husband have been using a diaphragm and contraceptive jelly as their only means of contraception. They have a pattern of drinking heavily on weekends and having unprotected intercourse. Which of the following is the most appropriate next step?

O A) Evaluate her for a sexually transmitted disease O B) Fit her with a diaphragm as requested O C) Help her to deal with her feelings about the abortion O D) Refer her to Alcoholics Anonymous O E) Talk to her about a nonbarrier method of contraception

28. A 15-year-old boy with sickle cell disease is brought to the physician because of pain of the arms and legs that has previously occurred several times at similar sites. Which of the following is the most likely cause of the pain?

O A) Bone infarct O B) Callus formation O C) Fracture O D) Muscle hemorrhage O E) Peripheral neuropathy

29. A 50-year-old man with schizophrenia develops fever, catatonia, and muscle rigidity 48 hours after starting treatment withchlorpromazine. His temperature is 39.2°C (102.5°F). Laboratory studies showmyoglobinemia and an increased serum creatine kinase activity. Which of the following is the most likely diagnosis?

O A) Acute dystonia O B) AkathisiaO C) Neuroleptic malignant syndrome O D) Parkinsonian syndrome O E) Tardive dyskinesia

30. A 21-year-old woman has received numerous transfusions of packed erythrocytes for treatment of homozygous p-thalassemia. Laboratory monitoring of her iron stores is necessary to avoid secondary iron overload. Which of the following laboratory measurements is most sensitive in assessing her iron stores?

O A) Ferritin O B) Haptoglobin O C) Iron saturation O D) Prealbumin O E) Transferrin

Lab Values F

31. A 16-month-old girl is brought to the physician for a routine examination. Physical examination shows hypertension, rapid eye movements, and a firm, nodular midline abdominal mass. Laboratory studies show increased urine concentrations of homovanillic and vanillylmandelic acids. Which of the following is the most likely cause of the findings in this patient?

O A) Aldosterone-secreting adenoma O B) Hepatoblastoma O C) Medulloblastoma O D) Nephroblastoma (Wilms tumor)O E) Neuroblastoma

32. A 55-year-old man comes to the physician because of maroon-colored stool for 3 weeks. Physical examination shows no abnormalities. Test of the stool for occult blood is positive. Colonoscopy shows a 4-cm mass at the splenic flexure. A biopsy specimen of the mass shows adenocarcinoma. This patient's cancer is most likely to next spread to which of the following organs?

O A) Bone O B) Brain O C) Liver O D ) Lung O E) Spleen

33. A 28-year-old man who is a construction worker is brought to the emergency department after his left arm was injured. An x-ray of the left upper extremity shows a comminuted spiral fracture of the humerus. Which of the following additional deficits is most likely in this patient?

O A) Ischemia of the forearmO B) Loss of function of muscles inneivated by the radial nerve O C) Rupture of the biceps muscle O D) Sensory loss on the palmar surface of the index finger O E) Sensory loss on the palmar surface of the small finger

34. A 40-year-old primigravid woman at 8 weeks' gestation comes to the physician for a routine prenatal visit. Her blood pressure is 150/90 mm Hg. Ultrasonography of the abdomen shows echogenic tissue without the presence of a fetus. A dilatation and curettage is performed, and the tissue removed is shown. This patient is at greatest risk for which of the following complications?

O A) Choriocarcinoma O B) Eclampsia O C) Ectopic pregnancy O D) Placenta accreta O E) Placenta extrachorialis O F) Placenta previa O G) Placental site trophoblastic tumor O H) Villitis of unknown cause

M ETR IC I I

35. An 83-year-old woman is seen by the physician at home because of increased confusion for the past 24 hours. She has a 7-year history of dementia, Alzheimer type, that has reached an advanced stage. Her temperature is 37.8°C (100°F), pulse is 116/min, respirations are 36/min, and blood pressure is 85/60 mm Hg. Physical examination shows decreased alertness and clouding of the lenses bilaterally but is otherwise unremarkable. Laboratory studies show:

Despite treatment, her blood pressure continues to decrease and she dies 24 hours later. Renal tissue obtained at autopsy is shown. Which of the following is the most likely diagnosis?

O A) Goodpasture syndrome O B) Hemolytic-uremic syndrome G C) Hepatorenal syndrome O D) PyelonephritisO E) Rapidly progressive glomerulonephritis O F) Renal tuberculosis

Leukocyte count 20,500/mm3Urinalysis

WBCRBCProtein

50/hpf 30/hpf 100 mg/dL

!6. A 57-year-old man dies 7 days after the sudden onset ofincoordination, ataxia, and a loss of sensation on the right half of his face and the left side of his trunk and extremities. At autopsy, there is softening of the areas of the brain indicated by the arrow in the photograph. The lesion that accounts for these clinical findings is in the distribution of which of the following arteries?

O A) Anterior inferior cerebellar O B) Basilar O C) PontineO D) Posterior inferior cerebellar O E) Superior cerebellar

37. A 67-year-old man with small cell carcinoma of the lung develops antibodies directed against the P/Q-type calcium channel. He is ; increased risk for developing a neurologic syndrome that most closely resembles that produced by which of the following toxins?

O A) Botulinum O B) Diphtheria O C) Organophosphate O D) Strychnine O E) Tetanus

Lab Values F

38. A 3-month-old boy is brought to the physician because of a 2-month history of frequent crying and tremulousness that usually occur 3 to 4 hours after feeding. He has been breast-fed since birth. Physical examination shows fat cheeks, massive hepatomegaly, and thin extremities. After a 4-hour fast, serum studies show metabolic acidosis, a decreased glucose concentration, and increased concentrations of lactic acid, uric acid, triglycerides, and cholesterol. Deficiency of which of the following hepatic enzymes is the most likely cause of the disorder in this patient?

O A) Fructose-1-phosphate aldolase O B) Galactose-1-phosphate uridyltransferase O C) Glucose-6-phosphatase O D) Hepatic lipaseO E) Medium-chain acyl-CoA dehydrogenase

39. A 56-year-old man comes to the physician for a follow-up examination. He has type 2 diabetes mellitus that is well controlled with metformin. Physical examination shows no abnormalities. Laboratory studies show a hemoglobin Alc of 6% and positive urine albumin. Treatment with enalapril is initiated. Which of the following structures will most likely be affected by this treatment and result in decreased urine protein excretion?

O A) Efferent glomerular arterioles O B) Macula densa O C) Renal collecting ducts O D) Renal juxtaglomerular cells

40. A 35-year-old man comes to the physician because of a painful perianal mass for 2 weeks. His vital signs are within normal limits. Physical examination shows a 2-cm erythematous, warm, swollen mass superior to the anal verge. Lancing of the mass releases a sanguineous exudate. The wound is irrigated and bandaged, and antibiotics are administered. Which of the following inflammatory mediators is most likely released from the aggregated platelets in this patient?

O A) lnterleukin-1 (IL-1)O B) Nitric oxide O C) Prostacyclin (PGy O D) Thrombin O E) Thromboxane A2

41. A 54-year-old woman comes to the physician because of a 2-week history of severe heartburn and regurgitation of gastric contents at bedtime. Use of an over-the-counter antacid decreased her symptoms but caused moderately severe diarrhea in the morning. Which of the following ingredients in the antacid is the most likely cause of the diarrhea in this patient?

O A) Aluminum hydroxide O B) Calcium carbonate O C) Magnesium trisilicate O D) Simethicone O E) Sodium bicarbonate

42. A 21 -year-old man is admitted to the hospital after being hit by a hockey stick. He has fractures of the nasal bones and cerebrospinal fluid rhinorrhea. On the third hospital day, he develops a fever, lethargy, and a stiff neck. Analysis of cerebrospinal fluid shows:

Leukocyte count 2010/mm3Neutrophils 92%Lymphocytes 8%

Erythrocytes 20/mm3Protein 190 mg/dLGlucose 12 mg/dL

A Gram stain of the cerebrospinal fluid is shown. Which of the following bacterial products promotes virulence of the infecting organism?

O A) Capsular polysaccharide O B) Endotoxin O C) M protein O D) Shiga-like toxin O E) Urease

Lab Values F

43. A previously healthy 32-year-old man is unconscious after an overdose of a sedative drug. His pulse is 90/min, respirations are 6/min, and blood pressure is 80/40 mm Hg. Arterial blood gas analysis on room air shows:

pH 6.8Pco2 80 mm HgPo2 40 mm HgHC03- 12 mEq/L

Which of the following best describes this patient's acid-base status?

O A) Metabolic acidosis with respiratory compensation O B) Respiratory acidosis and metabolic acidosis O C) Respiratory acidosis with metabolic compensation O D) Uncompensated metabolic acidosis O E) Uncompensated respiratory acidosis

44. A healthy 40-year-old woman inhales to total lung capacity and then exhales forcefully. The rate of expiratory airflow is highest at total lung capacity and decreases linearly as exhalation continues. Which of the following is the most likely cause of the observed decrease in expiratory airflow?

O A) Airway compression O B) Decreased expiratory effort O C) Decreased intrapleural pressure O D) Doming of the diaphragm O E) Increased elastic recoil

45. A 65-year-old man has exertional dyspnea and a mild, nonproductive cough. He is using his accessory muscles for respiration. X- rays of the chest show a flattened diaphragm, bronchovascular patterns that do not extend to the periphery of the lung, and a cardiac silhouette that is lengthened and narrowed. Which of the following changes in the respiratory airway is most likely in this patient?

O A) Adenocarcinoma in tracheal wall O B) Distention of air spaces distal to terminal bronchi O C) Increased alveolar secretions O D) Purulent secretions in the mainstem bronchi O E) Tracheal stenosis

46. A 6-month-old boy is brought to the physician by his mother because of a 3-day history of fever and cough. His mother says that he has been sickly since birth. He was admitted to the hospital on two previous occasions because of severe diarrhea and pneumonia. He is below the 5th percentile for length and weight. His temperature is 39°C (102.2°F). Physical examination shows diffuse erythroderma with pustules in the diaper area. Coarse bilateral breath sounds are heard on auscultation of the chest. A chest x-ray shows diffuse bilateral pulmonary infiltrates. Despite appropriate treatment with antibiotics, the patient dies 3 days later. At autopsy, Pneumocystis jiroveci (formerly P. carinii) pneumonia is identified as the cause of death. His thymus is markedly decreased in size. Karyotype is normal. He has decreased circulating serum immunoglobulin concentrations. A photomicrograph of a biopsy specimen of the thymus is shown. Which of the following is the most likely cause of this patient's condition?

O A) Congenital HIV infection O B) Cystic fibrosis O C) DiGeorge syndrome O D) Severe combined immunodeficiency O E) Wiskott-Aldrich syndrome

47. A 24-year-old woman with asthma comes to the physician for a follow-up examination. At her last visit, the physician prescribed an inhaled corticosteroid to be used twice daily along with an inhaled p2-adrenergic agonist as needed for acute episodes. The patient has had continued wheezing and shortness of breath twice weekly during the day and two to three times monthly at night. The patient says she stopped using the inhaled corticosteroid because it did not relieve her symptoms. The lungs are clear to auscultation of the chest. In addition to counseling the patient about appropriate inhaler usage technique, it is most appropriate for the physician to encourage inhaled corticosteroid usage by stating which of the following?

O A) "I understand completely if you want to see another physician for a second opinion about your treatment options."O B) "If you don't follow your medication regimen as I have directed, you may have to find another physician."O C) "It's not a good idea to stop taking any medications without talking to a physician first."O D) "Let's discuss the potential consequences that will likely occur if you don't follow your medication regimen."O E) "Let's review how the inhaled corticosteroid will help in the control of your symptoms."

48. An investigator is conducting a study of a possible link between the development of breast cancer and an environmental toxin in a particular community. Over a 1-year period, all of the women with established breast cancer in a certain zip code are identified. Which of the following best describes this measurement?

O A) Attack rate O B) Cumulative incidence O C) Incidence O D) Period prevalence O E) Point prevalence

49. During an experiment on an isolated nerve-muscle preparation, calcium concentrations are measured in various compartments. Following stimulation of the nerve, a contraction is elicited. Which of the following in the muscle is most likely to have an increased calcium concentration as a result of the elicited contraction?

O A) Cytoplasm O B) Extracellular fluid O C) Mitochondria O D) Sarcoplasmic reticulum O E) T-tubules

50. A 3-year-old boy is brought to the physician by his parents because of fever, sore throat, malaise, and lethargy for 2 days. He and his family recently immigrated to the USA, and he has not received any routine childhood immunizations. His temperature is 39.4°C (103°F). Physical examination shows an erythematous pharynx with patches of a tough, gray, membrane-like material that bleeds if it is removed. There is cervical lymphadenopathy. A throat culture grows Corynebacterium diphtheriae. Immunization with which of the following would most likely have prevented this illness?

O A) Capsular polysaccharide O B ) Mprotein O C) Outer membrane protein O D) Protease