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A 50-year-old man comes to the physician because of a 2-week history of progressiveshortness of breath while climbing stairs to his office every morning. He reports no otherproblems, but he is concerned because his father had a major myocardial infarction at the ageof 52 years. His pulse is 110/min and regular, respirations are 16/min, and blood pressure is135/95 mm Hg. The lungs are clear to auscultation. Cardiac examination shows normal heartsounds with a physiologic split of S 2 . Stress echocardiography shows hypokinesis of theposterior left ventricle with increasing activity levels. Which of the following is the mostlikely cause of the posterior left ventricular findings in this patient?A) Disruption of the sympathetic nerves to the left ventricleB) Extravascular compression of the coronary arteriesC) Increased left ventricular end-diastolic pressureD) Increased myocardial oxygen consumption) Stenosis of the right coronary arteryA 75-year-old woman comes to the physician because of a 3-month history of an enlarging lesion on her face. Physical examination shows a 1.5-cm, brown-black, mottled, scaly lesion with irregular borders. Microscopic examination of a biopsy specimen of the lesion shows atypical melanocytes spread along thebasilar layer of the epidermis. Which of the following is the most likely causeof these findings?A) Acanthosis nigricansB) Actinic keratosisC) Compound nevusD) Lentigo malignaE) Seborrheic keratosisA 13-year-old boy is scheduled to receive chemotherapy for a leukemia thathas the histologic features of malignant lymphocytes. This neoplasm is furthertyped for cell surface and intracellular markers specific for lymphocyte subsets.The neoplastic cells do not express the following markers: CD4, CD8, surface IgM, surface IgG, cytoplasmic IgM and μ - heavy chain, cytoplasmic IgG, and γ -heavy chain. The leukemic cells express class I MHC molecules and showrearrangement of the T-ly mphocyte receptor β -chain gene D and J segments.Which of the following is the normal counterpart of these malignantlymphocytes? A) Activated cytolytic effector T lymphocytes in the circulationB) Mature IgM-secreting B lymphocytes in the lymph nodeC) Mature immunoglobulin-secreting plasma cells in the lymphnodeD) Pre-B lymphocyte progenitor of mature B lymphocytes in thebone marrowE) T-lymphocyte thymocytes localized to the thymic cortexA 70-year-old man has a 4-month history of weight loss, abdominal pain, anddiarrhea. Stool analysis shows increased excretion of neutral fat and musclefiber. A D -xylose test for carbohydrate absorption shows no abnormalities.Examination of tissue obtained on intestinal biopsy shows no abnormalities.This patient is most likely to respond favorably to administration of which of the following agents?A) AntibioticsB) AzathioprineC) Intrinsic factorD) Pancreatic enzymesE) PrednisoneA 20-year-old woman comes to the physician because her menstrual period is1 week late. Menses had occurred at regular 28-day intervals. She hadunprotected sexual intercourse with her boyfriend 20 days ago. A urinepregnancy test result is positive. Which of the following best describes thestage of development of the embryo at this time?A) The cytotrophoblast is present, but the syncytiotrophoblast hasnot yet formedB) Gastrulation is complete, but there are only two germ layersC) The neural plate is present, but the neural tube is not yetcompleteD) Placental development is complete, but the embryo is resistantto teratogensE) The sclerotome cells have begun migrating, but the somites have not yet formedA 5-year-old boy is stung on his foot by a bee. Within 30 minutes the local areais edematous. The extravascular accumulation of fluid is most directly relatedto which of the following?A) Demargination of leukocytesB) Fibrin thrombiC) Gap formation between endothelial cellsD) VasoconstrictionE) VasodilationThe vaccine against diphtheria confers protective immunity by inducing theformation of antibodies against a preparation composed of which of thefollowing?A) Killed bacterial cellsB) Live attenuated bacterial cellsC) Purified bacterial peptidoglycanD) Purified capsular polysaccharideE) Purified inactivated toxinA 2-month-old girl is brought to the physician for a follow-up examination 2days after a complete blood count was found to be abnormal. Her blood groupis A, Rh-positive. She was born at term to a healthy 23-year-old woman whoseblood group is O, Rh-positive. Birth weight was 3890 g (8 lb 9 oz). Pregnancyand delivery were uncomplicated. The patient has been active and feeding well.Her temperature is 37.6°C (99.7°F), pulse is 120/min, and respirations are30/min. Physical examination shows no abnormalities. Laboratory studies done since birth are shown. Patient Age 24 Hours 1 Week 1 Month Hemoglobin (g/dL) (N=11−15) 16.9 15.7 12.7 Hematocrit (%) (N=28−45) 51 49 39Leukocyte count (/mm 3 ) (N=5000−19,500) 17,200 15,600 12,900Segmented neutrophils 4% 3% 5%Eosinophils 4% 4% 2%Basophils 4% 2% 1%Lymphocytes 69% 73% 77%Monocytes 19% 18% 15%Platelet count (/mm 3 ) (N=150,000−400,000) 185,000 198,000 205,000Which of the following is the most likely diagnosis?A) Alloimmune hemolytic disease of the newbornB) Congenital cytomegalovirus infectionC) Congenital neutropeniaD) DiGeorge syndromeE) Severe combined immunodeficiencyA 50-year-old man comes to the emergency department because of a 2-week history of progressive shortness of breath. His pulse is 90/min, respirations are26/min, and blood pressure is 120/80 mm Hg. Physical examination shows noother abnormalities. Laboratory studies show:Arterial P CO 2 30 mm HgArterial P O 2 96 mm HgArterial O 2 content 12 vol% (N=17% – 21%)Mixed venous P O 2 36 mm HgMixed venous O 2 content8 vol% (N=10% – 16%)Which of the following is the most likely explanation for these findings?A) AnemiaB) Drug-induced alveolar hypoventilationC) Residence at a high altitudeD) Severe regional mismatching of alveolar ventilation andpulmonary capillary perfusion
