Block

Answers

8-1 through 8-2. The answers are 8-1 c, 8-2 d. (Sadock, 7/e, p 962.) Alcohol withdrawal delirium (delirium tremens) is the most severe form of alcohol withdrawal. In this syndrome, coarse tremor of the hands, insomnia, anxiety, agitation, and autonomic hyperactivity are accompanied by severe agitation, confusion, and tactile or visual hallucinations. When alcohol use has been heavy and prolonged, withdrawal phenomena start within 8 h of cessation of drinking. Symptoms reach peak intensity between the second and the third day of abstinence and are usually markedly diminished by the fifth day. In a milder form, withdrawal symptoms may persist for weeks as part of a protracted syndrome. Wernicke's psychosis is an encephalopathy cause by severe thiamin deficiency and usually associated with prolonged and severe alcohol abuse. It is characterized by confusion, ataxia, and ophthalmoplegia. In alcohol hallucinosis, vivid auditory hallucinations start shortly after cessation or reduction of heavy alcohol use. Hallucinations may present with a clear sensorium and are accompanied by signs of autonomic instability that are less prominent than in alcohol withdrawal delirium.

Benzodiazepines are the preferred treatment for alcohol withdrawal delirium. Diazepam and chlordiazepoxide are the most commonly used. Elderly patients, or patients with severe liver damage, may better tolerate intermediate-acting benzodiazepines, such as lorazepam and oxazepam. Thiamin (100 mg) and folic acid (1 mg) are routinely administered to prevent central nervous system (CNS) damage secondary to vitamin deficiency. Thiamin should be always administered prior to glucose infusion, because glucose metabolism may rapidly deplete the patient's thiamin reserves in cases of long-term poor nutrition. When the patient has a history of alcohol withdrawal seizures, magnesium sulfate should be administered.

8-3. The answer is a. (Schwartz, 7/e, pp 688-689.) Flail chest is diagnosed in the presence of paradoxical respiratory movement in a portion of the chest wall. At least two fractures in each of three adjacent ribs or costal car tilages are required to produce this condition. Complications of flail chest include segmental pulmonary hypoventilation with subsequent infection and ultimately respiratory failure. Management of flail chest should be individualized. If adequate pain control and pulmonary toilet can be provided, patients may be managed without stabilization of the flail. Often intercostal nerve blocks and tracheostomy aid in this form of management. If stabilization is required, external methods such as sandbags or towel clips are no longer used. Surgical stabilization with wires is used if thoracotomy is to be performed for another indication. If this is not the case, "internal" stabilization is performed by placing the patient on mechanical ventilation with positive end-expiratory pressure. Tracheostomy is recommended because these patients usually require 10 to 14 days to stabilize their flail segment and postventilation pulmonary toilet is simplified by tracheostomy. Indications for mechanical ventilation include significant impedance to ventilation by the flail segment, large pulmonary contusion, an uncooperative patient (e.g., owing to head injury), general anesthesia for another indication, fractures of more than five ribs, and the development of respiratory failure.

8-4. The answer is d. (Fauci, 14/e, pp 543-546.) The lesion has characteristics of melanoma (pigmentation, asymmetry, irregular border), and a full-thickness excisional biopsy is required. Shave biopsy of a suspected melanoma is always contraindicated. Diagnosis is urgent; the lesion cannot be observed over time. Once the diagnosis of melanoma is made, the tumor must then be staged to determine prognosis and treatment.

8-5. The answer is e. (Behrman, 16/e, pp 977-981. McMillan, 3/e, pp 1107-1110. Rudolph, 20/e, pp 639-642.) To prove a diagnosis of infectious mononucleosis, a triad of findings should be present. First, physical findings can include diffuse adenopathy, tonsillar enlargement, an enlarged spleen, small hemorrhages on the soft palate, and periorbital swelling. Second, the hematologic changes should reveal a predominance of lymphocytes, with at least 10% of these cells being atypical. Third, the characteristic antibody response should be present. Traditionally, heterophil antibodies can be detected when confirming a diagnosis of infectious mononucleosis. These antibodies may not be present, however, particularly in young children. Alternatively, specific antibodies against viral antigens on the Epstein-Barr virus can be measured. Antibodies to viral capsid antigen (VCA) and to anti-D early antigen are elevated prior to the appearance of Epstein-Barr nuclear antigen (EBNA) and are, therefore, markers for acute infection. Immunoglobulin G (IgG) VCA and EBNA persist for life, whereas anti-D disappears after 6 mo.

8-6. The answer is a. (Wallace, 14/e, p 1055. USPSTF, 2/e, p 585.) The findings are typical of cocaine use during pregnancy, which has also been associated with impaired fetal growth and increased risk of placenta abruptio. Infants exposed to opiates during pregnancy may exhibit symptoms of withdrawal. Fetal alcohol syndrome is characterized by microcephaly, stunting, flattened nasolabial facies, and narrow palpebral tissues. Human immunodeficiency virus (HIV) infection is asymptomatic at birth.

8-7. The answer is d. (Fauci, 14/e, pp 1474-1475.) The patient most likely has a spontaneous pneumothorax. This disorder affects tall, thin men and may be recurrent. It is thought to be due to the rupture of subpleural blebs in response to high negative intrapleural pressures. Physical examination often reveals unilateral chest expansion, decreased fremitus, hyperresonance, and diminished breath sounds. Patients with chronic obstructive pulmonary disease (COPD), cystic fibrosis, Pneumocystis carinii pneumonia (PCP), and tuberculosis may have blebs and are at risk for secondary pneumothorax.

8-8. The answer is a. (Speroff, 6/e, pp 392-403. Adashi, pp 990-1006.) In North America, any pubertal changes before the age of 8 years in girls and 9 years in boys are regarded as precocious. Although the most common type of precocious puberty in girls is idiopathic, it is essential to ensure close long-term follow-up of these patients to ascertain that there is not serious underlying pathology, such as tumors of the central nervous system or ovary. In only 1% to 2% of patients with precocious puberty is an estrogen-producing ovarian tumor the causative factor. McCune-Albright syndrome (polyostotic fibrous dysplasia), also relatively rare, consists of fibrous dysplasia and cystic degeneration of the long bones, sexual precocity, and café au lait spots on the skin. Hypothyroidism is a cause of precocious puberty in some children, making thyroid function tests mandatory in these cases. Tumors of the central nervous system as a cause of precocious puberty occur more commonly in boys than in girls; they are seen in about 11% of girls with precocious puberty.

8-9. The answer is a. (Tierney, 39/e, pp 1088-1090.) Acromegaly (hypersecretion of growth hormone after closure of the epiphyses) is almost always caused by a pituitary adenoma (benign 99% of the time). Patients present with tall stature, large hands and feet, prominent mandible, prognathism, coarse facial features, wide tooth spacing, deep voice, macroglossia, and carpal tunnel syndrome. Patients may have headache, visual field defects, hypertrophy of the laryngeal tissue causing obstructive sleep apnea, hypertension, cardiomegaly, multiple skin tags, premalignant colonic polyps, and diabetes mellitus. Gigantism occurs before the closure of the epiphyses. Amyloidosis is a group of disorders characterized by infiltration of various organs (kidney, heart, intestine, endocrine) by protein fibrils. Patients with amyloidosis may have macroglossia and carpal tunnel syndrome. Macro-glossia is also seen in hypothyroidism. Coarse features may run in families (familial prognathism).

8-10. The answer is a. (Schwartz, 7/e, pp 552-553.) Cystosarcoma phyl-loides is a tumor most often seen in younger women. It can grow to enormous size and at times ulcerate through the skin. Still, it is a lesion with low propensity toward metastasis. Local recurrence is common, especially if the initial resection is inadequate. Simple reexcision with adequate margins is curative. Very large lesions may necessitate simple mastectomy to achieve clear margins. Axillary lymphadenectomy, however, is seldom indicated without biopsy-positive demonstration of tumor in the nodes. The low incidence of metastatic disease suggests that adjunctive therapy is indicated only for known metastatic disease, even when the tumors are quite large and ulcerated.

8-11. The answer is e. (Holmes, 3/e, ch 80, pp 1117-1120, Eur. Mod. Deliv. Collab., Lancet, 1999.) The landmark randomized placebo controlled trial ACTG 076 demonstrated that zidovudine (ZDV) given at the beginning of the second trimester, during labor and delivery, and to the newborn for 6 wk significantly reduced the transmission of HIV to the newborn from 25.5% in the control group to 8.3% in the treatment group. Thus, ZDV can be highly effective for primary prevention in the newborn. Other promising treatment schedules with ZDV and other antiretrovirals are under study. Recent data demonstrates that a cesarean section can reduce vertical transmission, but it should not supersede antiretroviral therapy. Currently, it appears that it is not a routinely recommended procedure for HIV-infected pregnant women, but this may change in the future. HIV can be transmitted by breast feeding, and in some studies the risk is increased by 14%. However, breast feeding has no impact on the highest risk of transmission, which occurs during gestation, labor, and delivery. Early identification of newborns at risk of HIV infection will guide the medical management and improve outcomes. It has no impact on the primary prevention of the infection to the newborn. Finally, all HIV-infected women should be made aware of the benefit of ZDV so they can make informed choices.

8-12. The answer is b. (Stobo, 23/e, pp 245-251.) The symptoms of Raynaud's phenomenon, arthralgia, and dysphagia point toward the diagnosis of sclerodema. Antinucleolar antibody occurs in only 20% of patients with the disease, but a positive test is highly specific. Cardiac involvement may occur, and an electrocardiogram (ECG) could show heart block or pericardial involvement. Renal failure can develop insidiously. Rheumatoid factor is nonspecific and present in about 20% of patients with sclerodema.

8-13. The answer is d. (Tierney, 39/e, pp 501-505.) The differential diagnosis for microcytic hypochromic anemia is TICS (Thalassemia, Iron deficiency, Chronic disease, and Sideroblastic). This patient of Mediterranean descent most likely has thalassemia trait. Thalassemia generally produces a greater degree of microcytosis for any given level of anemia than does iron deficiency. Target cells are seen in this disorder, but are also seen in lead poisoning, liver disease, hyposplenism, and hemoglobin C disease. The most common cause of a microcytic anemia is iron deficiency but it is unlikely in this asymptomatic patient with a negative fecal occult blood test (FOBT). The mean corpuscular volume (MCV) in anemia of chronic disease is usually normal or slightly reduced; patients typically have a history of chronic infection or inflammation, cancer, or liver disease. Alcoholics, patients taking antituberculosis medication or chloramphenicol, or those with lead poisoning may develop sideroblastic anemia (a failure to incorporate heme into protoporphyrin). Bone marrow staining will demonstrate iron deposits (ringed sideroblasts) encircling the nucleus in siderocytes. Coarse basophilic stippling of the red blood cells on peripheral smear is characteristic of lead poisoning.

8-14. The answer is b. (Goldman, 21/e, pp 211-213.) Systolic dysfunction is an inability of the ventricle to contract normally (hypodynamic).

Patients (especially older patients) with hypertension and diabetes mellitus are predisposed to diastolic dysfunction (inability of the ventricle to relax for filling); typically, these patients have an S4 gallop, elevated filling pressures, and a hyperdynamic (ejection fraction >50%) ventricle. Patients with left heart failure present with pulmonary congestion (i.e., crackles). Patients with right heart failure present with jugular venous distension (JVD), S3 gallop, hepatomegaly, ascites, and peripheral edema.

8-15. The answer is c. (Mishell, 3/e, pp 330-339.) Although there is an increased risk of spontaneous abortion, and a small risk of infection, an intrauterine pregnancy can occur and continue successfully to term with an intrauterine device (IUD) in place. However, if the patient wishes to keep the pregnancy and if the strings are visible, the IUD should be removed in an attempt to reduce the risk of infection, abortion, or both. Although the percentage of ectopic pregnancies may be increased, the majority of pregnancies occurring with an IUD are intrauterine. Therefore, in the absence of signs and symptoms suggestive of an ectopic pregnancy, especially after ultrasound documentation of an intrauterine pregnancy, laparoscopy is not indicated.

8-16. The answer is c. (Schatzberg, 2/e, p 812.) Common side effects of methylphenidate include loss of appetite and weight, irritability, oversensi-tivity and crying spells, headaches, and abdominal pain. Insomnia may occur, particularly when this agent is dispensed late in the day. Tics, while a less frequent complication of stimulant treatment, can cause significant impairment. Choreiform movements and night terrors are side effects of another stimulant, pemoline. Leukopenia and cardiac arrhythmias are not associated with stimulant treatment.

8-17. The answer is e. (Patten, 2/e, p 375.) This woman probably has trigeminal neuralgia (tic douloureux). The treatment options for this facial pain disorder include carbamazepine (Tegretol). Although carbamazepine is a potent antiepileptic medication, other antiepileptic medications such as phenobarbital and divalproex sodium (Depakote) are usually ineffective in blunting the pain. Phenytoin (Dilantin) is another antiepileptic useful in the management of trigeminal neuralgia, and recently gabapentin (Neurontin) has had some success as well. Analgesics and antiinflammatory drugs such as indomethacin (Indocin) are notably ineffective in managing this disorder.

8-18. The answer is b. (Fauci, 14/e, pp 1469-1472.) The clinical situation described is characteristic of pulmonary embolic disease. In greater than 80% of cases, pulmonary emboli arise from deep venous thromboses (DVTs) of the lower extremities. DVTs often begin in the calf, where they rarely if ever cause clinically significant pulmonary embolic disease. However, thromboses that begin below the knee frequently grow, or propagate, above the knee; clots that dislodge from above the knee cause clinically significant pulmonary emboli, which, if untreated, cause mortality exceeding 80%. Interestingly, only about 50% of patients with DVT of the lower extremities have clinical findings of swelling, warmth, erythema, pain, or "cords." As long as the superficial venous system, which has connections with the deep venous system, remains patent, none of the classic clinical findings of DVT will occur because blood will drain from the unobstructed superficial system. When a clot does dislodge from the deep venous system and travels into the pulmonary vasculature, the most common clinical findings are tachypnea and tachycardia; chest pain is less likely and is more indicative of concomitant pulmonary infarction. Arterial blood gas (ABG) is usually abnormal, and a high percentage of patients exhibit hypoxia, hypocapnia, alkalosis, and a widening of the alveolar-arterial gradient (P). ECG is frequently abnormal in pulmonary embolic disease. The most common finding is sinus tachycardia, but atrial fibrillation, pseudoinfarction in the inferior leads, and right and left axis deviation are also occasionally seen. Initial treatment for suspected pulmonary embolic disease includes prompt hospitalization and institution of intravenous heparin provided there are no contraindications to anticoagulation.

8-19. The answer is b. (Fauci, 14/e, pp 1470-1471.) Lung scanning is the principal imaging test for the diagnosis of pulmonary embolus. The diagnosis is very unlikely in patients with normal or near normal scans. The diagnosis is highly likely in patient with high probability scans. In patients with a high clinical index of suspicion for pulmonary embolus but low probability scan, the diagnosis becomes more difficult, and pulmonary angiography may be indicated. About two-thirds of patients with pulmonary embolus have evidence of deep venous disease on venous ultrasound. Therefore, pulmonary embolus cannot be excluded by a normal study. The quantitative D-dimer enzyme-linked immunoabsorbent assay is positive in 90% of patients with pulmonary embolus in some studies. It has been used to rule out pulmonary embolus in a patient with a low or intermediate probability scan.

8-20. The answer is e. (Behrman, 16/e, pp 1418-1421. McMillan, 3/e, pp 290-291, 1431-1432. Rudolph, 20/e, pp 1452-1453.) Congestive heart failure from any cause can result in mild cyanosis, even in the absence of a right-to-left shunt, and in poor peripheral pulses when cardiac output is low. Congestive heart failure from many causes can be associated with a rapid pulse rate (up to 200 beats/min). A pulse rate greater than 250 beats/min, however, should suggest the presence of a tachyarrhythmia. Common causes for supraventricular tachycardia include Wolff-Parkinson-White syndrome (WPW), congenital heart disease, and sympathomimetic drugs. In this patient, evaluation for WPW and cardiac abnormalities must be accomplished after the congestive heart failure from the increased heart rate is under control.

8-21. The answer is d. (Berson, pp 30-35,121-122.) Ischemic optic neuropathy usually occurs in patients with a history of diabetes or hypertension (underlying vascular disease). The disc is pale and swollen with splinter hemorrhages. This disorder is due to occlusion of the posterior ciliary arteries with subsequent production of edema. Central artery occlusion is sudden and painless. It is usually due to infarction from a thrombus or embolus and causes the retina to become pale. The thin tissue of the macula area appears as a cherry red spot. Occlusion of the retinal vein occurs due to slow venous blood flow and thrombosis. Patients complain of a slowly progressing loss of vision. The funduscopic image of retinal vein occlusion is so dramatic that it is often described as "blood and thunder." In retinal detachment, the fundus appears elevated and often has folds. Patients complain of acute vision loss after noticing flashing lights, floaters, and then a shade over the eye. Diabetic retinopathy may be proliferative or nonproliferative. In nonproliferative (background) disease, retinal findings include microaneurysms, dot-and-blot hemorrhages, hard exudates, and macular edema. Proliferative diabetic retinopathy (neovascularization with the formation of fragile vessels) is a response to continuous retinal ischemia and is responsible for most blindness in diabetes mellitus. Hypertensive retinopathy is classified by the Keith-Wagener-Barker classification:

Grade 1: arteriolar narrowing and copper wiring Grade 2: grade 1 changes plus arteriovenous nicking Grade 3: grade 2 changes plus hemorrhages and exudates Grade 4: grade 3 changes with the addition of papilledema

8-22. The answer is a. (Scott, p 753. Rock, 8/e, pp 1088-1089.) When patients present with urinary incontinence, a urinalysis and culture should be performed. In patients diagnosed with a urinary tract infection, treatment should be initiated and the patient should then be reevaluated. It is not uncommon for symptoms of urinary leakage to resolve after appropriate therapy. Initial evaluation of the incontinent patient includes a history and physical examination, UA/CS, simple cystometrogram, check for residual urine, stress test, and urinary diary.

8-23. The answer is c. (Stobo, 23/e, pp 288-290.) The patient has diastolic hypertension with associated hypokalemia. She is not taking diuretics. There is no edema on physical exam. Excessive inappropriate aldosterone production will produce a hypertension with hypokalemia syndrome. Hypersecretion of aldosterone increases distal tubular exchange of sodium for potassium with progressive depletion of body potassium. The hypertension is due to increased sodium absorption. Very low plasma renin that fails to increase with appropriate stimulus (such as volume depletion) with hypersecretion of aldosterone suggests the diagnosis of primary hyperaldos-teronism. Suppressed resin activity occurs in about 25% of hypertensive patients with essential hypertension. Lack of suppression of aldosterone is also necessary to diagnose primary aldosteronism. High aldosterone levels that are not suppressed by saline loading prove that there is a primary inappropriate secretion of aldosterone.

8-24. The answer is b. (Chin, 17/e, p 442. Fauci, 14/e companion hbk., pp 402-403.) Persons with sickle-cell disease have functional asplenism due to infarction. This results in impaired immune response to polysaccharide antigens, such as Streptococcus pneumoniae, Haemophilus influenzae, and Neisseria meningitidis. They are more susceptible to invasive Salmonella infection, which is often not preceded by enteric symptoms. Localization of a systemic infection often results in osteomyelitis. Persons with sickle cell disease are also more susceptible to malaria.

8-25. The answer is a. (Behrman, 16/e, pp 1191-1193. McMillan, 3/e, pp 1711-1712. Rudolph, 20/e, pp 1120-1121.) The causes of pancreatitis in children are varied, with about one-fourth of cases without predisposing etiology and about one-third as a feature of another systemic disease. Traumatic cases are usually due to blunt trauma to the abdomen. Acute pancre atitis is difficult to diagnose; a high index of suspicion is necessary. Common clinical features include severe pain with nausea and vomiting. Tenderness, guarding, rebound pain, abdominal distension, or paralytic ileus are signs and symptoms often seen. No diagnostic test is completely accurate. An elevated total serum amylase with the correct clinical history and signs and symptoms is the best diagnostic tool. Plain films of the abdomen exclude other diagnoses; ultrasonography of the pancreas can reveal enlargement of the pancreas, gallstones, cysts, and pseudocysts. Supportive care is indicated until the condition resolves.

8-26. The answer is c. (Schwartz, 7/e, pp 494-496.) Because of the ease with which carbon dioxide diffuses across the alveolar membranes, PaC02 is a highly reliable indicator of alveolar ventilation. In this postoperative patient with respiratory acidosis and hypoxemia, the hypercarbia is diagnostic of alveolar hypoventilation. Acute hypoxemia can occur with pulmonary embolism, pulmonary edema, and significant atelectasis, but in all those situations the C02 partial pressures should be normal or reduced as the patient hyperventilates to improve oxygenation. The absorption of gas from the peritoneal cavity may transiently affect the PaC02, but should have no effect on oxygenation.

8-27. The answer is b. (Fauci, 14/e, p 2102.) The patient is presenting with symptoms of normal menopause, which may include hot flashes, urinary frequency, dysuria, urinary incontinence, vaginal dryness, vaginal itchiness, and dyspareunia. Patients also have amenorrhea. Patients may become anxious or depressed during this time, but there is no evidence that personality or mood changes are due to menopause.

8-28. The answer is c. (Fauci, 14/e, p 1705. Tierney 39/e, p 675.) Patients with cirrhosis may have erythema of the palms, spider angiomas, decreased body hair, gynecomastia, testicular atrophy or menstrual irregularities, and parotid and lacrimal gland enlargement. Many of these changes are due to hormonal disturbances (the production of estrogen). Patients with cirrhosis may also have clubbing of the fingers. Portal hypertension may cause caput Medusae (prominent abdominal vasculature), splenomegaly, and ascites. Patients may have jaundice and signs of hepatic encephalopathy (asterixis). The Child classification is a factor that determines survival in patients with end-stage liver disease; the patient described most likely has Child class C cirrhosis (6-mo survival of 50%).

Child Class A

Child Class B

Child Class C

Bilirubin

<2.0

2.0-3.0

>3.0

Albumin

>3.5

3.0-3.5

<3.0

Ascites

None

Easily controlled

Not controlled

Neurologic

None

Minimal

Advanced (coma)

Nutrition

Excellent

Good

Wasting

8-29. The answer is c. (Mishell, 3/e, pp 198-202.) Although all the procedures mentioned in the question can be helpful in establishing a case of rape in most situations, the expected lack of sperm and the matching blood types in the situation presented would limit their value in this case. Only the finding of 50 U/mL or more of acid phosphatase in this woman's vagina could be taken as evidence of ejaculation. Her introitus probably would not be injured because of her parity. Foreign pubic hair might only indicate close contact.

8-30. The answer is a. (Lewis, 2/e, pp 676-678.) Separation anxiety disorder is characterized by manifestations of distress when the child has to be separated from loved ones. The distress often leads to school refusal, refusal to sleep alone, multiple somatic symptoms, and complaints when the child is separated from loved ones, and at times may be associated with full-blown panic attacks. The child is typically afraid that harm will come either to loved ones or to him- or herself during the time of separation.

8-31. The answer is d. (Tierney, 39/e, pp 1104-1106.) Symptoms of hypothyroidism include constipation, depression, edema, tongue thickening, cold intolerance, Queen Anne sign (missing lateral one-third of eyebrows), muscle cramps, weight gain, goiter, amenorrhea, galactorrhea, pleural effusion, pericardial effusion, cardiomegaly, bradycardia, hypothermia, hyponatremia, anemia, and hypertension. Patients are said to have hung-up reflexes (a prolonged relaxation phase). Amiodarone has a high iodine content and causes hypothyroidism in 8% of patients. Myxedema is a rare complication of hypothyroidism; patients present with coma, severe hypotension, hypothermia, hypoventilation, and hypoxemia. Cretinism is congenital (infantile) hypothyroidism.

8-32. The answer is d. (Ransom, pp 53-54.) Condyloma acuminatum is a sexually transmitted disease caused by the human papillomavirus (HPV). For many years, application of podophyllum was the treatment of choice for vulvar warts. Because podophyllum can produce peripheral neuropathy, bone marrow depression, and occasionally death, most physicians recommend the application of trichloroacetic acid to the vulva; however, because of systemic absorption, neither medication should be applied to extensive vaginal lesions. Laser surgery and cryotherapy result in high recurrence rates because of the difficulty of reaching all areas of the vagina. Since the vaginal condylomas are generally flat, optimal medical management includes the topical application of 5% 5-fluorouracil cream.

8-33. The answer is d. (Adams, 6le, p 1486.) Malignant hyperthermia is characterized by acute severe fever, tachypnea, tachycardia, and rigidity, and high mortality rate if left untreated. It is typically precipitated by volatile anesthetics, especially halothane, or muscle relaxants such as suc-cinylcholine. Patients may become severely acidotic and develop rhab-domyolysis. Pathology shows diffuse segmental muscle necrosis. It appears to be a metabolic myopathy, in which there is abnormal release of calcium from the sarcoplasmic reticulum and ineffectual uptake afterward. Genetic defects in the ryanodine receptor, involved in calcium flux in the sar-coplasmic reticulum, are responsible for about 10% of cases, although as yet unidentified abnormalities of this or related proteins probably play a role in most cases. It is inherited in an autosomal dominant fashion. Certain other myopathies, including Duchenne muscular dystrophy and central core myopathy, are associated with this condition as well. Treatment consists of discontinuation of anesthesia, administration of dantrolene, which prevents release of calcium from the sarcoplasmic reticulum, and supportive measures.

8-34. The answer is c. (Alexander, 9le, pp 885-886.) Paroxysmal supraventricular tachycardia typically displays a narrow QRS complex without clearly discernable P waves, with rate in the range of 160 to 190 beats/min. The rate is faster in atrial flutter. Atrial fibrillation would show an irregularly irregular rate. Wide QRS complexes would be expected in ventricular tachycardia.

8-35. The answer is c. (Behrman, 16le, pp 910-914. McMillan, 3le, pp 951-953, 2160-2162. Rudolph, 20le, pp 582-583.) Lyme disease, caused by the spirochete Borrelia burgdorferi and transmitted mostly by ticks of the ioxodes family, is characterized by a unique skin lesion, recurrent attacks of arthritis, and occasional involvement of the heart and central nervous system. Illness usually appears in late summer or early fall, 2 to 30 days after a bite by an infecting tick. Erythema chronicum migrans begins as a red macule, usually on the trunk at the site of tick attachment, that enlarges in a circular fashion with central clearing. Nonspecific systemic signs include headache, fever, and malaise. Joint involvement generally occurs days to years after onset of the rash. Cardiac disease consists primarily of disturbances of rhythm. Involvement of the central nervous system is evidenced by headache and stiff neck. The diagnosis should be suspected when any of the signs and symptoms occur, because the disease can present in an atypical manner. The characteristic lesion of erythema chronicum migrans as well as the history of tick bite are frequently not noted by the patient. It is not until late joint, heart, or neurologic manifestations occur, and Lyme disease is suspected, that serologic evidence confirms the etiology. Sero-logic evidence is sought when the patient has spent time in summer months in endemic areas or there is a risk of tick bite. Treatment with penicillin or tetracycline results in a faster resolution of symptoms and prevention of later complications, especially if given early in the course of the disease.

8-36. The answer is b. (Adams, 6/e, p 1212.) Acute poisoning with arsenic may cause tonic-clonic seizures or a less dramatic encephalopathy. Hemolysis may be substantial and mucosal irritation evident. Death may develop with circulatory collapse if the dose of arsenic is substantial enough. The polyneuropathy that develops with chronic poisoning is resistant to treatment with chelating agents, such as BAL. If the patient survives the poisoning, peripheral nerve damage resolves over the course of months or years.

8-37. The answer is a. (Fauci, 14/e, pp 1182-1185.) Chloroquine-resistant malaria is an increasing problem, and Plasmodium vivax and falci-parum malaria may be multidrug resistant. Because of the increasing spread and intensity of plasmodium resistance, the Centers for Disease Control and Prevention recommends a weekly dose of mefloquine for all travelers. Chemoprophylaxis is never entirely reliable, and malaria must always be considered in the differential diagnosis of fever in patients who have traveled to endemic areas. Trypanosomiasis, caused by the protozoan Trypanosoma cruzi, is a parasitic illness found only in the Americas. Patients present with the Romana sign (unilateral and painless edema of the perioc-ular tissues) and cardiomyopathy (Chagas disease). Patients with toxoplas-mosis who are immunocompetent are generally asymptomatic and have self-limiting disease.

8-38. The answer is b. (DSM-IV, 4/e, pp 292-296.) Schizoaffective disorder is characterized by depressive or manic episodes superimposed on symptoms of chronic schizophrenia. This patient experienced a persistence of psychotic symptoms in the absence of prominent affective symptoms and consequently fits the criteria for a diagnosis of schizoaffective disorder. Although affective symptoms may be present in schizophrenia, they are not prominent. In psychotic depression, psychotic symptoms are always associated with prominent affective symptoms. Delusional disorder is characterized by one or two nonbizarre, well-organized delusions and is not accompanied by significant mood disturbances.

8-39 through 8-40. The answers are 8-39 e, 8-40 e. (Schwartz, 7/e, pp 1646-1649.) This patient presents with the symptoms of a pheochromocy-toma. These tumors can initially become symptomatic during pregnancy. A noninvasive workup should be performed. Ultrasonography of the abdomen is frequently sufficient to localize the tumor to the right or left adrenal; an abdominal computed tomography (CT) scan with its large dose of radiation should be avoided in pregnancy. The treatment can be early excision of the pheochromocytoma, and in three cases in pregnant women this was done with survival of two of the three infants. A therapeutic abortion, especially at 18 wk, is not indicated, and cesarean section would not produce a viable fetus. The current approach is a- and ^-adrenergic blockade followed by vaginal delivery or cesarean section with excision of the tumor at the same time as delivery or electively after delivery. Metyrosine (Demser) inhibits tyrosine hydroxylase and results in a decrease in endogenous levels of catecholamines. This form of treatment, coupled with term delivery, is also acceptable.

8-41. The answer is e. (Adams, 6/e, p 1070.) Essential tremor comes on during action and remits when the limb is relaxed, unlike the tremor of Parkinson's disease. It often affects the head as well as the arms, also unlike Parkinson's disease. Patients are often very disturbed by the tremor, particularly as it leads to a great deal of social embarrassment. There is no asso ciated slowness of activity (bradykinesia), rigidity, or cognitive disturbance. Patients frequently report improvement with ingestion of alcohol, to the extent that some patients may resort to use of alcohol on a chronic basis to reduce their symptoms. Although it is often referred to as familial tremor, there is some disagreement on this point since it may simply be the case that patients with the condition are more likely to refer relatives for evaluation. Beta blockers and primidone may be used to treat this condition.

8-42. The answer is e. (Speroff, 6/e, pp 392-403.) These gonadotropin-releasing hormone (GnRH) results and luteinizing hormone (LH) pulses are seen in normal puberty. Normal signs of puberty involve breast budding (thelarche, 9.8 years), pubic hair (pubarche, 10.5 years), and menar-che (12.8 years). Besides an increase in androgens and a moderate rise in follicle-stimulating hormone (FSH) and LH levels, one of the first indications of puberty is an increase in the amplitude and frequency of nocturnal LH pulses. In patients with idiopathic true precocious puberty, the pituitary response to luteinizing hormone-releasing hormone (LHRH) is identical to that in girls undergoing normal puberty. Iatrogenic sexual precocity (i.e., the accidental ingestion of estrogens), premature thelarche, and ovarian tumors are examples of sexual precocity independent of LH function.

8-43. The answer is e. (Fauci, 14/e, p 463.) Anorexia occurs predominantly in females, and begins either before or shortly after puberty. Binge eating may occur, although it is uncommon and more closely associated with bulemia. Weight is decreased in anorexia, whereas it is near normal in bulimia. Ritualized exercise is usual in anorexia, but not in bulemia. Amen-orrhea is always present in anorexia because of weight loss. Antisocial behavior is more frequently associated with bulimia than with anorexia, and the depression in bulemia tends to be more severe than in anorexia, making suicide a definite risk.

8-44. The answer is d. (Schwartz, 7/e, pp 1244-1246.) Carcinoid tumors arise from the neuroectoderm and are a type of apudoma. The most common site of carcinoid tumors is the small bowel, although appendiceal car-cinoids are also common. Carcinoid syndrome, which is characterized by flushing, diarrhea, and cardiac valvular disease, occurs in a small percentage of patients with carcinoid tumors; it is rarely seen with appendiceal carcinoids. It occurs when serotonin is released into the systemic circulation and thus avoids breakdown by the liver. The appropriate therapy for a small carcinoid (less than 2 cm) of the appendix is simple appendectomy.

8-45. The answer is a. (Fauci, 14/e, pp 713-717.) The onset of multiple myeloma is usually insidious with weakness and fatigue. Pain caused by bone involvement, anemia, renal insufficiency, and bacterial pneumonia often follow. This patient presented with fatigue and bone pain and then developed bacterial pneumonia probably secondary to Streptococcus pneu-moniae, an encapsulated organism for which antibodies to the polysaccha-ride capsule are not adequately produced by the myeloma patient. There is also evidence for renal insufficiency. Hypercalcemia is frequently seen in patients with multiple myeloma and may be life threatening.

8-46. The answer is b. (Fauci, 14/e, pp 713-717.) Definitive diagnosis is made by demonstrating >10% plasma cells in bone marrow. None of the other findings are specific enough for definitive diagnosis. Renal biopsy would not be helpful.

8-47. The answer is a. (Behrman, 16/e, pp 1520-1522. McMillan, 3/e, pp 1477-1479, 1488, 1490-1491, 1493-1507, 2162-2165, 2176-2177. Rudolph, 20/e, pp 486-489, 497, 1241-1242, 1271-1275.) The mean age of presentation of immune thrombocytopenic purpura (ITP) is 6 years. Patients look well except for petechial rash. Patients with acute lym-phoblastic leukemia frequently have symptoms of pallor and fever in addition to bleeding. Nearly 50% have hepatomegaly and splenomegaly. CBC reveals anemia, leukocytosis or leukopenia, and thrombocytopenia. DIC is secondary to a severe underlying disease, such as fulminant bacterial sepsis with hypotension or profound hypoxia. Patients invariably appear ill and have leukocytosis, thrombocytopenia, and abnormal coagulation studies [e.g., prolonged prothrombin time (PT) and partial thromboplastin time (PTT)], decreased fibrinogen concentration, and elevated fibrin split products). Patients with Henoch-Schonlein purpura have symptoms of skin rash and abdominal or joint pain. The rash is usually urticarial and purpuric and is present over the buttocks or lower extremities. The platelet count is normal or elevated. Systemic lupus erythematosus (SLE) is very rare in 3-year-old children. Findings include fever, joint pain, and skin rash. CBC can reveal anemia, leukopenia, and thrombocytopenia.

8-48. The answer is e. (Behrman, 16/e, pp 974, 977, 1088. McMillan, 3/e, pp 436-437. Rudolph, 20/e, pp 684-686.) Varicella-zoster immunoglobulin (VZIG) should be administered to the infant immediately after delivery if the mother experienced the onset of varicella within 5 days prior to delivery, and immediately upon diagnosis if her chickenpox started within 2 days after delivery. If untreated, about half of these infants will develop serious varicella as early as 1 day of age. If a normal full-term newborn is exposed to chickenpox 2 or more days postnatally, VZIG and isolation are not necessary because these babies appear to be at no greater risk for complications than older children. Acyclovir is not approved for use in early infancy.

8-49. The answer is c. (Rosner, 5/e, ch 13.5, pp 603-605; ch 13.4, pp 592-594.) Since the crude and the gender-adjusted relative risks are the same, we can conclude that gender is not a confounder (using the change-in-estimate definition of confounding). However, the relative risk for men is different than for women. We conclude that gender is an effect modifier. Effect modification is a different concept than confounding. Confounding is a nuisance factor that needs to be eliminated because it causes a distortion of the results, simply because the factor in question is distributed unevenly in exposed and unexposed individuals. Effect modification provides important information: the magnitude of the effect of a particular exposure on the outcome will vary according to the presence of a third factor—in this case, gender. It is not related to the fact that there may be more men than women in one group or another. A third factor can be both a con-founder and an effect modifier if the adjusted risk differs from the crude risk, in addition to having different risks in women and in men. It may be neither a confounder nor an effect modifier if the adjusted and crude risks are the same and if the rates in men and women are the same. Finally, it could be only an confounder if the crude and adjusted risks differ, but the rates between men and women are the same. Stratification can be used to evaluate both confounding and effect modification: it will eliminate confounding and describe effect modification.

8-50. The answer is c. (Sadock, 7/e, p 1007.) Cocaine inhibits the normal reuptake of norepinephrine and dopamine, causing an increase of the concentration of these neurotransmitters in the synaptic cleft. This mechanism is responsible for the euphoria and sense of well-being that follow cocaine use, but it also causes excessive sympathetic activation and diffuse vasoconstriction. High blood pressure, mydriasis, cardiac arrhythmias, coronary artery spasms, and myocardial infarcts are all seen with cocaine intoxication. Other toxic effects of cocaine include headaches, ischemic cerebral and spinal infarcts, subarachnoid hemorrhages, and seizures. Intoxications with PCP, cannabinoids, opiates, and LSD present with different symptoms and signs.

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