MCQs samples نماذج للاختيار من متعدد(نماذج من أسئلة الامتحانات مع الاجابات النموذجية)٠
26. A 70-year-old woman has been in long-standing poor health, with severe diabetes mellitus and rheumatoid arthritis. Her physician notes that she appears pale and orders a hematocrit, which shows a result of 35%. Examination of the blood smear reveals a microcytic anemia. The physician is considering a differential diagnosis of iron deficiency anemia versus anemia of chronic disease. Which of the following laboratory determinations would be most helpful in distinguishing these conditions?
a)Erythrocyte:granulocyte ratio in bone marrow
b) Presence or absence of polychromatophilic target cells
c)Presence or absence of stippled erythrocytes
d)Serum ferritin
e)Serum iron
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27. A 45-year-old patient on hemodialysis for one week has noted that his blood pressure is more difficult to control. He reports good compliance with his medications, which include erythropoietin, ferrous sulfate, vancomycin, and vitamin D. His blood pressure is 180/99 mm Hg. Which of the following is the most likely cause for the worsening control of his blood pressure?
a)Erythropoietin
b)Ferrous sulfate
c)Vancomycin
d)Vitamin D
e) Uremia
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28. A 40-year-old man is brought to the emergency room by his friends. Apparently, he has ingested some unknown medication in a suicide attempt. The patient is disoriented to time. His temperature is 39.3 C (103 F), blood pressure is 120/85 mm Hg, pulse is 100/min and irregular, and respirations are 22/min. The skin is flushed and dry. Dilated pupils and muscle twitching are also noted on physical examination. ECG reveals prolonged QRS complexes. Hepatic transaminases are normal, and blood gas analysis shows a normal pH. These findings are most likely due to intoxication by which of the following substances?
a)Acetaminophen
b)Alcohol
c)Benzodiazepines
d)Clonidine
e) Monoamine oxidase (MAO) inhibitors
f)Tricyclic antidepressants
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29.A 72-year-old man comes to the physician because of a 3-day history of right-sided chest pain. He denies any shortness of breath, nausea or vomiting. Physical examination shows a unilateral, erythematous, maculopapular rash extending from the anterior chest wall around to the back in a dermatomal pattern. The remainder of the examination is normal. In conversation, he states that is he is going to visit his grandchildren next week and that their mother "doesn't believe in immunizations". His grandchildren are at increased risk for which of the following rashes?
a) Discrete maculopapular lesions that become confluent as they spread from "head to toe"
b)Dome-shaped papules with central umbilication
c)Expanding annular lesion with central clearing
d) "Slapped-cheek" appearance and a lacy reticular rash
e) Vesicles at various stages of evolution
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30. A 50-year-old man consults a physician because he has been having transient periods of rapid heart beat accompanied by sweating, flushing, and a sense of impending doom. Physical examination is unrevealing, with no evidence of arrhythmia at the time of the exam. However, the man's wife is a nurse, so the physician asks that she take vital signs the next time one of the episodes occurs. She does, and demonstrates a blood pressure of 195/140 mm Hg with heart rate 160/min during the episode. She promptly takes her husband to the emergency room, but the spell is over by the time that he is seen. Urinary measurement of which of the following would most likely be diagnostic in this case?
a) Dehydroepiandrosterone (DHEA)
b)Human chorionic gonadotropin (hCG)
c)17-ketosteroids
d)Vanillylmandelic acid VMA
e) Zinc protoporphyrin
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31. A 35-year-old woman consults an ophthalmologist because of double vision and droopy eyelids. She also has complaints of generalized muscle weakness. IV injection of edrophonium dramatically, but only briefly, reverses her symptoms. This patient's probable disease has a pathophysiologic basis that is closest to that of which of the following conditions?
a) Bullous pemphigoid
b)Diabetes mellitus type 1 (some cases)
c)Idiopathic Addison disease
d)Insulin resistance
e)Systemic lupus erythematosus
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32.A 34-year-old woman who is healthy without underlying medical problems presents to clinic with complaints of temperature up to 101 F and cough with greenish sputum production for 2 days without any dyspnea. Her heart rate is 88/min, and her respiratory rate is 18/min. There is no accessory muscle use or conversational dyspnea, nor are there wheezes, bronchial breath sounds, rales, or egophony over the right lower lung fields. Chest x-ray film reveals a right lower lobe consolidation. A CBC shows a leukocyte count of 13,000/mm3. Which of the following is the most appropriate pharmacotherapy?
a) Amoxicillin
b)Ampicillin-sulbactam
c)Ceftriaxone
d)Erythromycin
e) Erythromycin plus ceftriaxone
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33. A 23-year-old type 1 diabetic is brought to the emergency department after being found in a coma. The scent of acetone is present on the patient's breath. Urinary catheterization with subsequent dipstick analysis demonstrates marked positivity for glucose and ketones. Stat blood chemistries would most likely show which of the following values for the anion gap?
a) 6 mEq/L
b)11 mEq/L
c)13 mEq/L
d)15 mEq/L
e) 20 mEq/L
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34. A 70-year-old man presents to the emergency department with a 3-day history of right temporal headache, fever, and profound malaise. He appears acutely ill. His temperature is 39.5 C (103.1 F), blood pressure is 130/80 mm Hg, pulse is 98/min, and respirations are 24/min. Tenderness over the right temporal region is appreciated on palpation. The right temporal artery is tender and slightly nodular. Neurologic examination is normal, including funduscopic examination. However, visual acuity is reduced. Laboratory studies show:
Hematocrit 39.0%
Hemoglobin 10.9 g/dL
Leukocytes 8800/µL (neutrophils 68%)
Erythrocyte sedimentation rate 80 mm/hr
Which of the following is the most appropriate next step in management?
a)Measurement of intraocular pressure
b)Visual field assessment
c)Low-dose (10 mg/day) prednisone treatment
d)High-dose (60 mg/day) prednisone treatment
e) Temporal artery biopsy
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35.A 74-year-old woman presents to her physician for a postoperative medical visit. Three days ago, she underwent a left total knee replacement for severe osteoarthritis. She has a past medical history significant for type 1 diabetes mellitus and glaucoma. Her hospital course was uneventful. She continues to take daily NPH insulin and has good control of her blood glucose. She also takes oxycodone, which was given to her in the hospital for pain. She is involved in a physical therapy rehabilitation program at the local hospital. On review of her medications, which of the following is most acutely indicated at this time?
a) An ACE inhibitor
b)A nonsteroidal anti-inflammatory agent
c)Oral aspirin
d)Oral Coumadin
e) Subcutaneous unfractionated heparin
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36. A 37-year-old woman presents with complaints of severe heartburn with or without meals. She has a history of hypertension, which has been treated with captopril. She also has a history of Raynaud disease, multiple facial telangiectasias, and very taut skin on the dorsum of both hands. She has failed to obtain relief for her heartburn with large doses of antacids, ranitidine, or omeprazole. Esophageal manometry is ordered. Which of the following would be the most likely results of this test?
a) Decreased esophageal peristalsis and decreased LES pressure
b)Decreased esophageal peristalsis and increased LES pressure
c)Increased esophageal peristalsis and decreased LES pressure
d)Increased esophageal peristalsis and increased LES pressure
e) Normal esophageal peristalsis and normal LES pressure
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37. A 60-year-old woman consults a physician because of weakness, headaches, dizziness, and tingling in her hands and feet. Physical examination demonstrates multiple areas of bruising on the back of her forearms and shins. On specific questioning, she reports having had five nosebleeds in the past two months, which she had attributed to "dry air". Blood studies are drawn which show a platelet count of 1.2 × 106/µL, a red cell count of 5.1 ×106/µL, and a white count of 10,500/µL with a normal differential count. Review of the peripheral smear demonstrates many abnormally large platelets, platelet aggregates, and megakaryocyte fragments. No abnormal red or white blood cells are seen. Philadelphia chromosome studies are negative. Which of the following is the most likely diagnosis?
a)Chronic myelogenous leukemia
b)Myelofibrosis
c)Polycythemia vera
d)Primary thrombocythemia
e) Secondary thrombocythemia
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38. A 23-year old-dancer presents with a chief complaint of weakness. She denies any other symptoms, including nausea or vomiting. She denies diarrhea. Her blood pressure is 80/40 mm Hg. There is no edema and the lungs are clear. Laboratory analysis of serum shows:
Sodium 126 mEq/L
Potassium 2.2 mEq/L
Bicarbonate 29 mEq/L
Magnesium 2.0 mg/dL
Calcium 9.0 mg/dL
The most likely cause of the patient's weakness is an abnormality in which of the following?
a) Bicarbonate
b)Calcium
c)Magnesium
d) Potassium
e) Sodium
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39. A 43-year-old woman is admitted for new-onset of seizures in the setting of hyponatremia. At baseline, she is well educated and works as a computer marketer. Her medical history is remarkable for a long history of depression and alcoholism, with multiple visits to the Emergency Department for trauma. She was initially found in her hot apartment by paramedics. At that time, she was postictal, incontinent of urine, and oriented only to name. She was last seen at work 3 days ago. In the Emergency Department her systolic blood pressure is 70 mm Hg and her pulse is 130/min. Upon physical examination, she has dry mucous membranes, a jugular venous pressure of less than 5 cm, and diffuse ecchymoses on her face, body, and breasts. She proceeds to have two addition seizures in the Emergency Department that are controlled with intravenous lorazepam. Laboratory studies reveal a serum sodium of 115 mEq/L, potassium of 2.8 mEq/L, and bicarbonate of 32 mEq/L. Which of the following is the most appropriate next test to obtain?
a)Electroencephalogram (EEG)
b)Magnetic resonance imaging (MRI) of the head
c) Non-contrast computed tomography (CT) of the head
d)X-ray films of the skull
e)Lumbar puncture (LP)
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40.A 65-year-old West Texas farmer of Swedish ancestry has an indolent, pale, raised, waxy, 1.2-cm skin mass over the bridge of the nose. The mass has been slowly growing over the past 3 years. There are no enlarged lymph nodes in the neck. Other than a "weather-beaten" appearance for the rest of his exposed skin, the remainder of the physical examination is unremarkable. Which of the following is the most likely diagnosis?
a)Basal cell carcinoma
b)Invasive melanoma
c)Keratoacanthoma
d)Pyogenic granuloma
e)Squamous cell carcinoma
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41.A 22-year-old woman goes to the emergency department because she feels very weak and is having muscle cramping and fasciculations. Blood chemistry studies demonstrate a plasma potassium of 1.5 mEq/L. On questioning, she admits to chronic use of laxatives and diuretics to control her weight. Which of the following ECG changes would be most characteristic of changes related to her K+ level?
a)Increased U wave amplitude
b)Prolongation of the P wave
c)Shortening of the QT interval
d)Tall, symmetric, peaked T waves
e)Widening of the QRS complex
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42. A 34-year-old man presents with a swollen left knee of 2 days' duration. He denies any known trauma to that region and has no prior history of any musculoskeletal complaints. He is in otherwise excellent health. He is homosexual and practices safe sex with a single partner. On physical examination, his knee is swollen, tender to palpation, and erythematous and has a limited range of motion. An arthrocentesis is performed. Which of the following is most suggestive of a septic arthritis in this patient?
a)A complete blood cell count with 14,300 white blood cells per mL
b)A joint fluid aspirate with a white blood cell count of 28,000 per mL
c)A joint fluid aspirate with a white blood cell count of 36,000 per mL
d)A joint fluid aspirate with a white blood cell count of 48,000 per mL
e) A joint fluid aspirate with a white blood cell count of 93,000 per mL
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43. A 59-year-old man presents to the hospital complaining of cough. The patient describes a cough that has progressively worsened over the past 3 days, becoming more productive of yellowish sputum. He also reports one episode of shaking chills 2 days ago. His past medical history is remarkable for rheumatoid arthritis, for which he takes a nonsteroidal agent for pain control. On examination, his blood pressure is 140/90 mm Hg, and his pulse is 100/min. He has coarse breath sounds over his right base and a normal cardiac examination. Which of the following is the most appropriate diagnostic test for this patient?
a)High-resolution chest CT
b)Positron emission tomography (PET) scan of the lungs
c)MRI of the chest
d)Ventilation-perfusion scan
e)X-ray films of the chest, posterior-anterior (PA) and lateral views
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ANSWERs
26)
Explanation:
The correct answer is
D. This is a common clinical scenario in real life. Serum ferritin is markedly decreased in iron deficiency anemia and is normal to modestly elevated in anemia of chronic disease. This difference makes this test very useful in this setting. You should be aware that serum ferritin may behave like an acute phase reactant. Therefore, in an acute inflammatory situation, erythrocyte ferritin may be more reliable if serum ferritin is equivocal. Also, do not forget that iron deficiency anemia can complicate the anemia of chronic disease (e.g., gastrointestinal bleeding can complicate gastrointestinal cancers); in this situation, most physicians treat the apparent iron deficiency anemia and see to what degree the anemia corrects.
The erythrocyte:granulocyte ratio in bone marrow (choice A) is slightly decreased in both iron deficiency anemia and anemia of chronic disease, but may be markedly increased in sideroblastic anemias.
Polychromatophilic target cells (choice B) and stippled erythrocytes (choice C) are absent in both iron deficiency anemia and anemia of chronic disease, but may be present in sideroblastic anemias and other iron-utilization anemias.
Serum iron (choice E) is decreased in both iron deficiency anemia and anemia of chronic disease, but may be markedly increased in sideroblastic anemia.
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27)
Explanation:
The correct answer is
A. The patient most likely has a worsening of his blood pressure due to erythropoietin. This is seen in about 33% of dialysis patients.
Vitamin D (choice D), iron (choice B) and vancomycin (choice C) generally do not raise blood pressure.
The patient is now on dialysis and should not be uremic (choice E).
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28)
Explanation:
The correct answer is
F. This patient's clinical picture is consistent with intoxication with tricyclic antidepressants such as amitriptyline and imipramine. Toxic effects are mediated by peripheral anticholinergic activity and "quinidine-like" action. The anticholinergic effects include mydriasis, tachycardia, impaired sweating with flushed skin, dry mouth, constipation, and muscle twitching. Quinidine-like effects (due to block of sodium channels in the heart) result in cardiac arrhythmias, especially ventricular tachyarrhythmias. In this setting, prolongation of the QRS complex is particularly important in the diagnosis. QRS width is, in fact, an even more faithful parameter of drug toxicity than serum drug levels. In severe intoxication, patients will develop seizures, severe hypotension, and coma.
Acetaminophen (choice A) results in liver toxicity. Liver enzymes would be elevated.
Alcohol intoxication (choice B) manifests with respiratory depression, hypothermia, and coma.
The manifestations of benzodiazepine intoxication (choice C) are similar to alcohol inasmuch as central nervous system depression is common to both drugs. Thus, acute benzodiazepine intoxication produces stupor, coma, and respiratory depression.
The sympatholytic properties of clonidine (choice D) explain the clinical symptoms of intoxication. Clonidine overdose causes bradycardia, hypotension, miosis, and respiratory depression.
Monoamine oxidase (MAO) inhibitors (choice E) represent a second-line treatment for major depression. Overdose induces ataxia, excitement, hypertension, and tachycardia. Such reactions can be precipitated by concomitant ingestion of tyramine-containing foods (aged cheese and red wine, for example).
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29)
Explanation:
The correct answer is
E. This patient has herpes zoster, which is a reactivation of the varicella-zoster virus (VZV) that was dormant in the dorsal root ganglion. Zoster (shingles) affects individuals in the 6th to 8th decades. It is characterized by pain, fever, and a dermatomal erythematous → vesicular rash. Treatment includes antiviral therapy. Individuals with herpes zoster are contagious and can spread the VZV virus. Chickenpox (varicella) is characterized by a vesicular rash at various stages of evolution. The varicella vaccination is recommended at 12 months, however if the grandchildren have not been immunized, they may develop chickenpox.
Discrete maculopapular lesions that become confluent as they spread from "head to toe" (choice A) is the typical presentation of measles, which is caused by a paramyxovirus. It is associated with cough, conjunctivitis, coryza, and Koplik's spots.
Dome-shaped papules with central umbilication (choice B) is the description of molluscum contagiosum, caused by a poxvirus.
An expanding annular lesion with central clearing (choice C), also known as erythema chronicum migrans, is the rash of Lyme disease, caused by Borrelia burgdorferi (after a tick bite). The rash begins as an erythematous macule that expands with central clearing, leading to the typical "bull's eye" lesion
A" slapped-cheek" appearance and a lacy reticular rash (choice E) is the description of the rash of erythema infectiosum (Fifth disease), which is caused by parvovirus B16.
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30)
Explanation:
The correct answer is
D. This patient's history suggests pheochromocytoma. This rare (but often considered diagnostically) tumor is most often found in the adrenal medulla, although it can also be found in other tissues derived from neural crest cells. The tumor cells secrete catecholamine hormones or their precursors, which can cause either paroxysmal (as in this case) or persistent hypertension. Urinary metabolites of epinephrine and norepinephrine are vanillylmandelic acid (VMA) and homovanillic acid, so screening 24 hour urine collections for these substances can be helpful in establishing or excluding these diagnoses even in cases in which a physician does not observe one of the paroxysms and thus blood cannot be drawn for serum catecholamine levels at that time.
DHEA (choice A) is the adrenal androgen dehydroepiandrosterone (made by the adrenal cortex rather than the adrenal medulla), and is measured in serum in cases where adrenal virilism is suspected.
hCG (choice B) is human chorionic gonadotropin, and both serum and urine levels can increase in pregnancy or trophoblastic disease.
17-ketosteroids (choice C) are measured in urine during evaluation of congenital adrenal hyperplasia (a disorder of the adrenal cortex rather than medulla).
Zinc protoporphyrin (choice E) is measured in blood when evaluating possible porphyria.
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31)
Explanation:
The correct answer is D. This patient has myasthenia gravis, which was suspected based on the woman's clinical presentation and confirmed with the response to the short-acting anticholinesterase drug edrophonium. Myasthenia gravis is an autoimmune disease in which antibodies directed against the acetylcholine receptor of the muscle side of the neuromuscular junction block the ability of the receptor to bind to acetylcholine. Of the diseases listed above, only insulin resistance is produced by a similar mechanism, i.e. antibodies to insulin receptors block the receptors' ability to bind to insulin.
Bullous pemphigoid (choice A) is caused by antibodies directed against the basement membrane of the skin, which damage the basement membrane and cause blister formation.
Some cases of diabetes mellitus type 1 (choice B) and idiopathic Addison disease (choice C) are characterized by humoral, and probably cell-mediated, reactions against the cells in the endocrine tissue.
Systemic lupus erythematosus (choice E) has circulating and locally generated immune complexes mediating the pathophysiology.
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32)
Explanation:
The correct answer is
D. The first step in the approach to this patient with a community-acquired pneumonia is to categorize her condition according to the American Thoracic Society guidelines (1993), which are based on severity of illness, age, comorbidities, and the need for hospitalization. This patient does not meet the criteria for hospitalization (one of the following is needed: respiratory rate > 30 breaths/min, room air PaO2< 60 mm Hg, O2 saturation less than 90% on room air, or bilateral or multiple lobes involved), and she is younger than 60 years without any comorbidities. The most common organisms are Streptococcus pneumoniae, Mycoplasma pneumoniae, Chlamydia pneumoniae, Haemophilus influenzae, Legionella, and respiratory viruses. Recommended treatment is with erythromycin or a related macrolide, such as azithromycin or clarithromycin.
Amoxicillin (choice A) does not have broad enough coverage to include the organisms listed above.
Ceftriaxone (choice C) and ampicillin-sulbactam (choice B) are used for hospitalized patients with community-acquired pneumonia.
Erythromycin plus ceftriaxone (choice E) is reserved for patients who are severely ill and hospitalized.
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33)
Explanation:
The correct answer is
E. The patient is in diabetic ketoacidosis, as indicated by the acetone scent to the breath and the glucose and ketones in the urine. Diabetic ketoacidosis produces an increased anion gap, since the anion for the acid that is produced (acetoacetate) is not one of the usually measured ions. The anion gap is usually estimated by subtracting the sum of the Cl- and HCO3- concentrations from the plasma Na+ concentration; the normal value for the anion gap is 12 ± 4 mEq/L. Causes of increased anion gap include conditions that produce ketoacidosis (diabetes mellitus, alcoholism, starvation), renal failure with retained sulfate and phosphate, drugs or metabolites (salicylate or ethylene glycol poisoning), alkalosis with increased negative charge of protein anions, and dehydration (hemoconcentration).
6 mEq/L (choice A) is below the lower limit of normal. The anion gap may be decreased because of a decrease of negatively charged serum proteins (eg, in hypoalbuminemia), an increase in proteins carrying few negative charges (eg, hypergammaglobulinemia), or an increase in unmeasured cations (e.g., magnesium, calcium, or lithium).
The other values (choice B, C, and D) are within normal limits.
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34)
Explanation:
The correct answer is
D. The patient needs urgent treatment with high-dose prednisone for giant cell arteritis (i.e., temporal arteritis). This systemic disease overlaps with polymyalgia rheumatica in approximately 40% of cases. It affects elderly persons who present with fever, malaise, temporal headache, and scalp tenderness. Giant cell arteritis is a frequent cause of fever of unknown origin in the elderly. The leukocyte count may be entirely normal, while the erythrocyte sedimentation rate (ESR) is markedly elevated. This condition may involve arteries other than the superficial temporal artery, including the aortic branches. The most important reason to start prednisone therapy is to prevent blindness secondary to extension of the process to the ophthalmic artery. Prednisone should be administered in high doses (usually 60 mg/day).
Measurement of intraocular pressure (choice A) is appropriate to confirm a diagnosis of acute (narrow-angle) glaucoma. This gives rise to a characteristic acute symptomatology of painful, red eyes, blurred vision, and halos around lights.
Visual field assessment (choice B) is not indicated in this case.
High-dose prednisone may be slowly tapered to low-dose (10 mg/day) prednisone treatment (choice C) over a period of 2 months, once the acute phase has resolved. Low-dose prednisone is used for polymyalgia rheumatica.
Temporal artery biopsy (choice E) is performed routinely in any patient with clinical signs and symptoms of giant cell arteritis. It is positive in up to 80% of cases. It shows the characteristic giant cell-rich granulomatous reaction in the media, with destruction of the elastic lamina. The biopsy should be performed after starting corticosteroid treatment.
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35)
Explanation:
The correct answer is
D. This patient is post a total knee replacement and is currently not on any anticoagulation therapy. The risk of deep venous thrombosis (DVT) and subsequent pulmonary embolism is very high in this population, and it is the standard of care to initiate Coumadin or low-molecular-weight heparin postoperatively for a period of 6 weeks to 6 months.
An ACE inhibitor (choice A) is, in the long term, an excellent drug for this patient given her diabetes. In the post-surgical period, however, the greatest consideration should be given to the most pressing issue.
A nonsteroidal anti-inflammatory agent (choice B) does not appear to be indicated at this time, as the patient appears to have reasonable pain control with her opiate.
Oral aspirin (choice C) is an anti-platelet agent that has no role in the prevention of DVT.
Subcutaneous unfractionated heparin (choice E) is used for prevention of DVT in immobile patients or in hospitalized patients unable to ambulate. However, after orthopedic surgery, especially after joint procedures, its efficacy is very poor, given the increased venous stasis.
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36)
Explanation:
The correct answer is
A. This patient has the classic presentation of gastroesophageal reflux disease (GERD) in association with scleroderma. These patients have the deposition of collagen in the body of the esophagus, as well as the lower esophageal sphincter (LES). This results in the typical pattern of decreased esophageal peristalsis and the reduced ability of the LES to maintain its high pressures between swallowing. These patients are therefore at risk for severe GERD and subsequent complications of peptic stricture and Barrett's esophagus. Although there is no corrective therapy to improve esophageal motility or increase LES pressure, aggressive treatment is generally aimed at reducing acid production with the use of high doses of proton pump inhibitors. Nevertheless, many of these patients develop the long-term consequences of GER
D.
Choice B suggests achalasia, in which impaired esophageal peristalsis is often accompanied by a lack of lower esophageal sphincter relaxation.
Choice C doesn't describe any of the more common esophageal motor disorders.
Choice D suggests symptomatic diffuse esophageal spasm, particularly if the peristaltic waves were poorly organized.
Choice E would be seen in patients without esophageal motor disease.
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37)
Explanation:
The correct answer is
D. The most likely diagnosis is primary (essential) thrombocythemia. The condition is due to a clonal abnormality of a multipotent hematopoietic cell that produces megakaryocytic hyperplasia with resultant increased platelet count. Since the platelets are often abnormal, either a thrombotic or a hemorrhagic tendency may be seen. The platelet count may be as low as 500,000/µL or greater than 1,000,000/µL. The clinical presentation and laboratory findings illustrated in the question stem are typical. The other choices listed commonly must be excluded before a diagnosis of primary thrombocythemia is confirmed.
Chronic myelogenous leukemia (choice A) can be a cause of increased platelet count, but the absence of either a Philadelphia chromosome or a markedly increased white count argues against this possibility.
Myelofibrosis (choice B) can also cause thrombocythemia, but would likely show some abnormally shaped (often tear drops) red cells.
Polycythemia vera (choice C) can also cause thrombocythemia, but would be associated with an increased red cell mass.
Secondary thrombocythemia (choice E) is a reactive process that may occur in a variety of settings including chronic inflammatory disorders, acute infection, hemorrhage or hemolysis, tumors, iron deficiency, or splenectomy. Abnormal platelet forms are not usually seen on smears from these patients and platelet function tests are usually normal.
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38)
Explanation:
The correct answer is
D. The low potassium is the most likely cause of the weakness. The patient may be a diuretic abuser or may vomit as part of an eating disorder.
The high bicarbonate (choice A) may reflect an alkalosis, but should not cause symptoms like this.
The magnesium (choice C) and calcium (choice B) values are close to the normal range.
The low sodium (choice E) is not likely to cause weakness.
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39)
Explanation:
The correct answer is
C. The test of choice to rule out acute intracerebral hemorrhage (ICH) is the head CT without contrast, as it is widely available, relatively inexpensive, and has high levels of sensitivity and specificity for acute bleeding.
While EEG (choice A), may help localize a seizure focus, it has relatively poor specificity in establishing the etiologic basis of the seizure and may be difficult to obtain on an urgent basis.
Head MRI (choice B), is more expensive, less widely available, and more time-consuming than head CT. It also has less sensitivity for ICH within the first 48 hours.
X-ray films of the skull (choice D), while important in diagnosing skull fractures and such conditions as Paget's disease, have no role in the diagnosis of ICH.
Lumbar puncture (choice E), is one of the modalities used to diagnose subarachnoid hemorrhage (SAH). It is relatively contraindicated in ICH because it may precipitate a herniation syndrome in patients with large hematomas, and has less sensitivity for intracerebral bleeding than CT.
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40)
Explanation:
The correct answer is
A. Basal cell carcinoma affects sun-exposed areas, particularly the mid and upper face, in patients lacking protective pigmentation. One of its morphologic forms is that of a raised, waxy, pale lesion that grows very slowly and doesn't metastasize to lymph nodes.
Melanoma (choice B) would have presented as a pigmented lesion, with asymmetry, irregular borders, different colors, and a diameter of more than 0.6 cm. It would not appear as a raised, waxy, pale nodule.
Keratoacanthoma (choice C) grows very rapidly in a matter of weeks and has a scaly, rough appearance, with a core of keratin. If untreated, it eventually sloughs off.
Pyogenic granuloma (choice D) also grows very rapidly. It has the appearance of wet granulation tissue, with visible yellowish pus.
Squamous cell carcinoma (choice E) is usually an ulcer, rather than a nodule. In the face, it favors the lower lip. If present for several years, lymph node metastasis can sometimes occur.
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41)
Explanation:
The correct answer is
A. Both chronic laxative use and chronic diuretic use can produce hypokalemia. Severe hypokalemia, with plasma potassium <3 mEq/L, can markedly affect skeletal, smooth, and cardiac muscles. Skeletal muscle effects can include weakness, cramping, fasciculations, paralysis (with risk of respiratory failure), tetany, and rhabdomyolysis. Smooth muscle effects include hypotension and paralytic ileus. Cardiac muscle effects include premature ventricular and atrial contractions, tachyarrhythmias, and AV block. Additional ECG changes can include ST segment depression, increased U wave amplitude, and T wave amplitude less than U wave.
The changes illustrated in choices B, C, D, and E are characteristic of hyperkalemia.
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42)
Explanation:
The correct answer is
E. Septic arthritis will produce the highest joint fluid white blood cell counts, typically with counts of greater than 75,000 per cc. Non-inflammatory arthritis, such as osteoarthritis, will typically produce joint aspirate counts of less than 10,000. If septic arthritis is suspected based upon the aspirate white blood cell count, then appropriate antibiotics should be started, while awaiting cultures. Failure to initiate appropriate antibiotic therapy until final identification of the organism would potentially lead to irreversible joint destruction.
An elevated peripheral white blood cell count of 14,300 (choice A) may be seen in either a crystalline or septic arthritis and will not distinguish between the two.
Inflammatory arthritis, i.e. crystalline arthritis, will typically produce a joint fluid aspirate with a white blood cell count of approximately 25-50,000 (choices B, C, and D). Since the aspirated fluid is also routinely examined for crystals, differentiation of any cases of septic versus crystalline arthritis with borderline values for white blood cell count can usually be made on that basis.
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43)
Explanation:
The correct answer is
E. Although there has been considerable progress in imaging modalities available to the clinician for examination of the lung, the posterior-anterior (PA) and lateral chest x-ray films remain the screening test of choice, based on its wide availability, low cost, safety, and clinical usefulness.
The chest CT (choice A) has assumed an important role in imaging of the lungs, as it is able to better define the interstitium and airspaces of the lungs. As such, this patient may ultimately require a chest CT, but it should not be the initial imaging study performed here, as it is more costly, less widely available and exposes the patient to significantly more radiation than the plain x-ray film.
Positron emission tomography (PET) scanning (choice B) currently has limited clinical utility in the evaluation at hand. Its use in other areas of medicine and research is expanding, however, and it may play a larger role in pulmonary medicine in the future.
MRI (choice C) has played a revolutionary role in the evaluation of the brain and connective tissues, but its clinical role in imaging the chest is limited, especially in light of its cost.
A ventilation-perfusion scan (choice D) is the imaging test of choice for the screening of suspected pulmonary embolism.
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