Hardest Trivia Questions Quiz On USMLE

Both the omental bursa and the greater omentum are derived from the dorsal mesogastrium, which is the mesentery of the stomach region. The dorsal mesoduodenum (choice A) is the mesentery of the developing duodenum, which later disappears so that the duodenum and pancreas come to lie retroperitoneally. The pericardioperitoneal canal (choice C) embryologically connects the thoracic and peritoneal canals. The pleuropericardial membranes (choice D) become the pericardium and contribute to the diaphragm. The ventral mesentery (choice E) forms the falciform ligament, ligamentum teres, and lesser omentum.

Hyperlipidemia has been subclassified based on the lipid and lipoprotein profiles. Type 2a, which this patient has, can be seen in a hereditary form, known as familial hypercholesterolemia, and also in secondary, acquired forms related to nephritic syndrome and hyperthyroidism. The root problem appears to be a deficiency of LDL receptors, which leads to a specific elevation of cholesterol in the form of increased LDL. Heterozygotes for the hereditary form generally develop cardiovascular disease from 30 to 50 years of age. Homozygotes may have cardiovascular disease in childhood. Type 1 (choice A) is characterized by isolated elevation of chylomicrons. Type 2b (choice C) is characterized by elevations of both cholesterol and triglycerides in the form of LDL and VLDL. Type 3 (choice D) is characterized by elevations of triglycerides and cholesterol in the form of chylomicron remnants and IDL. Type 5 (choice E) is characterized by elevations of triglycerides and cholesterol in the form of VLDL and chylomicrons.

The fibrinolytic activity of streptokinase is due to its ability to bind and cleave plasminogen, producing plasmin. Plasmin directly cleaves fibrin, both between and within the fibrin polymers, thus breaking up thrombi and potentially restoring blood flow to ischemic cardiac muscle. This same mechanism of fibrinolysis is shared by urokinase and tissue-plasminogen activator (tPA). Antithrombin III (choice A) is a coagulation inhibitor that binds to and inactivates thrombin. Antithrombin III is anticoagulant, not fibrinolyti

Wine and cheese (and many other fermented foods) contain tyramine, an indirect sympathomimetic that can trigger excess
catecholamine release and lead to a hypertensive crisis when ingested by patients taking MAO inhibitors. The only such drug listed among the answer choices is phenelzine. Other MAO inhibitors with similar effects include tranylcypromine, isocarboxazid, and iproniazid. Whenever this particular drug class is mentioned in a question stem, consider the possibility of interactions with foods or other medications the patient may have taken. Amitriptyline (choice A) is a tricyclic antidepressant. Tricyclic antidepressant drugs (particularly amitriptyline) are known for their anticholinergic side effects. They also produce postural hypotension (because they block alpha-adrenergic receptors) and are sedative. Fluoxetine and sertraline (choices B and D) are antidepressants that are selective serotonin reuptake inhibitors (SSRIs). Fluoxetine is also useful in treatment of obsessive-compulsive disorders. Trazodone (choice E) is an atypical antidepressant with substantial sedative side effects. Its most serious side effect is priapism, a medical emergency.

Perforation of a peptic ulcer is potentially fatal, because of either peritonitis with sepsis or sudden exsanguination (if the perforation damages one of the many arteries of the stomach). Peptic ulcer disease, gastritis, and possibly gastric carcinoma and gastric lymphoma have been strongly associated with Helicobacter pylori colonization of the mucus layer covering the gastric mucosa. Colonization is associated with destruction of the mucus layer, thereby destroying its protective function. Cryptosporidium parvum (choice A) causes diarrhea that is severe in immunocompromised patients. Entamoeba histolytica (choice B) produces dysentery-like symptoms or can cause liver abscess. Escherichia coli (choice C) causes a variety of diarrheal diseases and can infect the bladder and soft tissues. Mycobacterium tuberculosis (choice E) causes tuberculosis, characterized by granuloma formation, especially in the lungs.

The disease is von Hippel-Landau disease, which is associated with a deletion involving the VHL gene on chromosome 3 (3p). Affected individuals develop vascular tumors (hemangioblastomas) of the retina, cerebellum, and/or medulla. Roughly half of the affected individuals later develop multiple, bilateral renal cell carcinomas. Berry aneurysms (choice A) are unrelated to hemangioblastomas, but are instead associated with adult polycystic disease. Peripheral nerve cancers (choice C) are a feature of von Recklinghausen's disease (neurofibromatosis type I). Choreiform movements, related to decreased GABA and acetylcholine (choice D), are a feature of Huntington's disease. Extremely high serum cholesterol (choice E) suggests the homozygous form of familial hypercholesterolemia.

Persons with this condition often perceive attacks and danger in relatively innocuous situations. They are quick to respond with anger, and, because personality disorders are ego-syntonic, individuals with personality disorders do not believe themselves to be in error. The individual with dependent personality disorder (choice A) does not confront others but wants others to take care of him. The individual with histrionic personality disorder (choice B) is flamboyant and seductive, not confrontational and angry. The individual with narcissistic personality disorder (choice C) is characterized by feelings of entitlement because they are so "special." And the individual with passive aggressive personality disorder (choice E) expresses anger indirectly (e.g., always being late) rather than confronting

The muscularis of the upper third of the esophagus (choice E) is composed entirely of striated muscle. The middle third (choice C) contains both striated and smooth muscle. The lower third (choice B) and lower esophageal sphincter (choice A) contain only smooth muscle. There is no such thing as the upper esophageal sphincter (choice D).

The structure of the cochlea is complex. The organ of Corti contains hair cells from the cochlear branch of the vestibulocochlear nerve (CN VIII). These cells rest on the basilar membrane (choice A), which separates the scala tympani (choice D) from the scala media. The hairs of the hair cells are embedded in the tectorial membrane, and movement of the basilar membrane below the cells tends to bend the hairs, which generates action potentials by the hair cells. The tectorial membrane that lies on the hair cells does not form a boundary between the different scala; the membrane separating the scala media from the scala vestibuli (choice E) is Reissner's (vestibular) membrane (choice C).

Because the right main bronchus is wider and more vertical than the left, foreign objects are more likely to be aspirated into the right main bronchus. The superior segmental bronchus of the lower lobar bronchus is the only segmental bronchus that exits from the posterior wall of the lobar bronchi. Therefore, if a patient is supine at the time of aspiration, the object is most likely to enter the superior segmental bronchus of the lower lobe. None of the segmental bronchi of the left lung (choices A and D) are likely to receive the object because the object is less likely to enter the left main bronchus. The apical segment of the right upper lobe (choice B) is not likely to receive the foreign object because of the sharp angle that the upper lobar bronchus makes with the right main bronchus and the sharp angle that the apical segmental bronchus makes with the lobar bronchus. The medial segmental bronchus of the right middle lobe (choice C) arises from the anterior wall of the right middle lobar bronchus. Therefore, when the patient is supine, the effect of gravity will tend to prevent the object from entering this segmental bronchus.

The pretracheal layer of the cervical fascia runs from the investing layers in both sides of the lateral neck and splits to enclose the thyroid gland. Superiorly, it attaches to the laryngeal cartilages; inferiorly, it fuses with the pericardium. As a result of these connections, the thyroid gland moves with laryngeal movements. The carotid sheath (choice A) contains the vagus nerve, internal jugular vein, carotid artery, and lymph nodes. The investing layer of the deep cervical fascia (choice B) splits to enclose the trapezius and sternocleidomastoid
muscles. The prevertebral fascia (choice D) covers muscles arising from the vertebrae. The superficial fascia (choice E) is immediately deep to the platysma muscle

Acute pyelonephritis is an infectious disease involving the kidney parenchyma and the renal pelvis. Gram-negative bacteria, such as Escherichia coli, Proteus, Klebsiella, and Enterobacter, are the most common causative organisms in acute pyelonephritis. Laboratory evaluation will often reveal leukocytosis with a left shift, and urinalysis typically shows pyuria, varying degrees of hematuria, and white cell casts. Since bacteremia is present, the patient should be hospitalized and empirically started on IV ampicillin and gentamicin. This regimen may be need to be changed, however, once the sensitivity results are available. Erythromycin (choice B) and tetracycline (choice E) are both bacteriostatic antibiotics and would not be recommended in a patient with a severe infection, such as acute pyelonephritis with bacteremia. Vancomycin (choice C) is primarily used in the treatment of severe gram-positive infections. Phenazopyridine (choice D) is a urinary analgesic, and nitrofurantoin (choice D) is a urinary tract anti-infective. Although nitrofurantoin is indicated for the treatment of "mild" cases of pyelonephritis, as well as cystitis, this patient's condition is severe and should be treated with appropriate antibiotics.

The functional residual capacity is the amount of air left in the lungs after a normal expiration. Because this volume cannot be expired in its entirety, it cannot be measured by spirometry. Essentially, lung volume that contains the residual volume, which is the amount of air remaining after maximal expiration (e.g., functional residual capacity and total lung capacity), cannot be measured by spirometry. These volumes can be determined using helium dilution techniques coupled with spirometry or body plethysmography. The expiratory reserve volume (choice A) is the volume of air that can be expired after expiration of a tidal volume. The inspiratory reserve volume (choice C) is the volume of air that can be inspired after inspiration of a tidal volume. Tidal volume (choice D) is the amount of air inspired or expired with each normal breath. Vital capacity (choice E) is the volume of air expired after a maximal inspiration

The patient has bilateral acoustic neuromas, probably due to neurofibromatosis type II (over 90% of patients with NF-2 develop bilateral acoustic neuromas). This condition is a associated with the NF-2, gene, located on 22q (note all the 2's). Patients often develop meningiomas, gliomas, and schwannomas of cranial and spinal nerves. 5q (choice A) contains the APC tumor suppressor gene, which is associated with familial and sporadic colorectal cancers. 13q (choice B) contains the Rb tumor suppressor gene, which is associated with retinoblastoma and osteosarcoma. 17q (choice C) contains both the NF-1 tumor suppressor gene, which is associated with neurofibromatosis type I, and the p53 tumor suppressor gene, associated with many human cancers. 18q (choice D) contains both the DCC gene, which is associated with colon and gastric carcinomas and the DPC gene, associated with pancreatic cancer.

The tumor is a neuroblastoma, which is one of the principal forms of cancer in children. Neuroblastoma typically occurs before age 5, with many presenting before age 2. Neuroblastoma can arise from neural crest cells throughout the body, but the adrenal medulla is the most common site. Homer-Wright pseudorosettes are circles of tumor cells with central young nerve fibers arising from the tumor cells. The oncogene associated with neuroblastoma is N-myc. erb-B2 (choice A) is associated with breast, ovarian, and gastric carcinomas. c-myc (choice B) is associated with Burkitt's lymphoma. L-myc (choice C) is associated with small cell carcinoma of the lung. ret (choice E) is associated with multiple endocrine neoplasia, types II and III.

Brucella abortus produces a chronic, granulomatous disease with caseating granulomas. Most cases occur in four states (Texas, California, Virginia, and Florida), and are associated with cattle, in which it produces spontaneous septic abortions. Most cases of brucellosis produce mild disease or fevers of unknown origin. However, Brucella spp. can infect the cardiovascular system and cause a localized infection. B. abortus is the most common species to cause endocarditis. The aortic valve is most commonly involved, followed by the mitral valve, and then both valves. Most cases of brucellosis are associated with occupational exposure, in persons such as veterinarians, ranchers, and those who handle carcasses. Bacillus anthracis (choice A) is the causative agent for anthrax. It usually produces cutaneous disease (malignant pustule or eschar) at the site of inoculation in handlers of animal skins. It can also produce a severe hemorrhagic pneumonia (Woolsorter's disease) and septicemia. At-risk groups include those who handle animal carcasses or skins. Coccidioides immitis (choice C) is a dimorphic fungal disease producing a granulomatous pulmonary syndrome that is more severe in dark-skinned individuals. Disseminated disease occurs most often in Filipinos, Mexicans, and Africans. The infective form is the arthrospore; the diagnostic form in tissue is the spherule containing endospores. The disease is endemic in the San Joaquin River Valley. At-risk groups include military personnel, agricultural workers, construction workers, oil field workers, archaeology students, participants in outdoor sports, and sightseers. Remote infections from fomites (cotton harvested in the Southwestern U.S.) have been reported. Erysipelothrix rhusiopathiae (choice D) is a pleomorphic, gram-negative rod that causes a localized skin infection. It is an occupational disease of fishermen, fish handlers, butchers, meat-processing workers, poultry workers, farmers, veterinarians, abattoir workers, and housewives. Trichinella spiralis (choice E) is a nematode infection caused by the ingestion of larvae found in undercooked meat. Pork is the most common contaminated meat. However, outbreaks in the northern parts of the U.S. have been associated with eating undercooked infected bear meat. Symptoms include diarrhea, periorbital edema, myositis, fever, and eosinophilia.

The neurohypophysis (posterior pituitary) is derived from an evagination of diencephalic neurectoderm. This structure is responsible for releasing oxytocin and vasopressin to the general circulation. Both hormones are synthesized in cell
bodies contained within the hypothalamus. ACTH (choice A), prolactin (choice D), and TSH (choice E) are all synthesized and released by the anterior pituitary, or adenohypophysis, which is derived from an evagination of the ectoderm of Rathke's pouch, a diverticulum of the primitive mouth. Remnants of this pouch may give rise to a craniopharyngioma in later life. Epinephrine

Bilirubin is a degradative product of hemoglobin metabolism. Bilirubin (pigment) stones are specifically associated with excessive bilirubin production in hemolytic anemias, including sickle cell anemia. Bilirubin stones can also be seen in hepatic cirrhosis and liver fluke infestation. Calcium oxalate stones (choice B) and cystine stones (choice E) are found in the kidney, rather than the gallbladder. Pure cholesterol stones (choice C) are less common than mixed gallstones, but have the same risk factors, including obesity and multiple pregnancies. Mixed stones (choice D) are the common "garden variety" gallstones, found especially in obese, middle aged patients, with a female predominance

This question is really asking you two things. First, it tests whether you know that lymphocytosis is associated with viral infection. Second, it tests your knowledge of lymphocytes' histological appearance. Note that these cells are generally small and normally constitute 25%-33% of leukocytes. Two types of lymphocytes have been distinguished: T cells (involved in cell-mediated immunity) and B cells (involved in humoral immunity). Monocytes are precursors of osteoclasts and liver Kupffer cells (choice B) and also give rise to tissue macrophages and alveolar macrophages. Platelets contain a peripheral hyalomere and central granulomere (choice C). Neutrophils have azurophilic granules and multilobed nuclei (choice D). They increase in number in response to bacterial infection. Erythrocytes remain in the circulation for about 120 days (choice E).

The smooth part of the right atrium (the sinus venarum) is derived from the sinus venosus. The coronary sinus and the oblique vein of the left atrium also derive from the sinus venosus. The bulbus cordis (choice A) gives rise to the smooth part of the right ventricle (conus arteriosus) and the smooth part of the left ventricle (aortic vestibule). The primitive atrium (choice B) gives rise to the trabeculated part of the right and left atria. The primitive ventricle (choice C) gives rise to the trabeculated part of the right and left ventricles. The truncus arteriosus (choice E) gives rise to the proximal part of the aorta and the proximal part of the pulmonary artery.

The disease is Fragile X Syndrome, which is a familial form of mental retardation that is roughly as common as Down's syndrome. The phenotype has a variable expression, but can include large head circumference at birth, perinatal complications (premature birth, asphyxia, seizures), and possibly increased incidence of sudden infant death syndrome. Later, mental retardation, particularly involving language, and symptoms suggestive of attention deficit disorder and/or autism may appear. Features suggestive of connective tissue disorder (lax skin and joints, flat feet, large ears) are common. After puberty, there may be a long narrow face with prominent jaw and nasal bridge. Macro-orchidism is also common after puberty. Mitral valve prolapse and aortic root dilatation, which may appear in late adolescence or
adulthood, are among the most serious complications of this disorder. Aortic regurgitation related to aortic root dilatation, not stenosis (choice A), can be a problem in this population. Common congenital cardiac malformations such as atrial septal defect (choice B) or ventricular septal defect (choice E) are not features of Fragile X syndrome, but can be seen with Down's syndrome.Tricuspid atresia (choice D) is a serious congenital cardiac malformation limiting flow into the right ventricle, but it is not part of Fragile X syndrome.

Sensitivity is defined as the ability of a test to detect the presence of a disease in those who truly have the disease. It is calculated as the number of people with a disease who test positive (true positive) divided by the total number of people who have the disease (true positive + false negative). In this case, sensitivity equals the number of people with HIV antibody who test positive (100) divided by the total number of people who have HIV antibody (120). This yields 100/120 = 83% (not a very sensitive test). 11% (choice A) corresponds to the prevalence of the disease in the tested population, which in this case equals the total number of people with HIV antibody (true positive + false negative = 100 + 20 = 120) divided by the total number of people tested (100 + 20 + 50 + 950 = 1120). This yields 120/1120 = 11%. 67% (choice B) corresponds to the positive predictive value of the test, which equals the number of people with the disease who test positive (true positives = 100) divided by the total number of people testing positive (all positives = 50). This yields 100/150 = 67%. 95% (choice D) corresponds to the specificity of the test, which equals the number of people without HIV antibody who test negative (950) divided by the total number of people without HIV antibody (10

The immunoperoxidase method uses horseradish peroxidase to produce a visible pigment when a specific antibody binds to antigenic sites in the tissue. Binding of the antibody to the epithelial cells indicates that the protein in question is being expressed by those cells. The positive immunoperoxidase results obtained here suggests that the channel protein is expressed in proximal convoluted tubular epithelium, since this is the only site in the kidney at which the epithelial cells have a "brush border." The brush border is made of microvilli, which enhance the proximal tubules' ability to reabsorb plasma constituents filtered at the glomeruli.

This patient has Tay-Sachs disease, an autosomal recessive disorder caused by the deficiency of hexosaminidase A, which leads to the accumulation of ganglioside GM2 in neurons, producing a degenerative neurologic disease. Children appear normal at birth, but then begin to suffer from diminished responsiveness, deafness, blindness, loss of neurologic function, and seizures. A cherry-red spot on the macula may be seen by ophthalmoscopic examination. Death usually occurs by 4 to 5 years of age. There is no therapy. The incidence is higher among Jews of Eastern European descent. Since the parents must be heterozygotes for the mutant hexosaminidase A allele, they would be expected to have diminished levels of the enzyme. A defect in the dystrophin (choice A) gene produces Duchenne muscular dystrophy, characterized by onset of weakness in early childhood. A severe deficiency in HGPRT (choice C) will lead to Lesch-Nyhan syndrome, characterized by excessive uric acid
production, mental retardation, spasticity, self-mutilation, and aggressive, destructive behavior. Deficiency of phenylalanine hydroxylase (choice D) results in classic phenylketonuria, a disease in which phenylalanine, phenylpyruvate, phenylacetate, and phenyllactate accumulate in plasma and urine. Clinically, there is a musty body odor and mental retardation. Hypophosphatemic rickets is an X-linked dominant condition causing abnormal regulation of vitamin D3 (choice E) metabolism and defects in renal tubular phosphate transport. Symptoms include growth retardation, osteomalacia, and rickets. --------------------

The cell pictured is an eosinophil, a member of the granulocytic lineage of white blood cells. The crystalline core of the granule contains a protein called the major basic protein, which appears to function in the destruction of parasites. Major basic protein also has deleterious effects on epithelial cells in patients with asthmatic reactions. The light component around the dense crystalline core contains products such as histaminase, arylsulfatase, and other enzymes. Lactoferrin (choice A) is found in the specific granules of the neutrophil. It inhibits the growth of bacteria by interfering with iron metabolism. Myeloperoxidase (choice C) is found in the azurophilic (large) granule of the neutrophil. This enzyme is also destructive to bacteria, destroying their cell walls. Histamine (choice D) is produced by the basophil and the mast cell. The histaminase of the eosinophil regulates the inflammatory reaction of these two cell types. Tartrate-resistant acid phosphatase (choice E) is a marker for hairy cell leukemia, a neoplasm of the B lymphocyte line. --------------------------------------------------------------------------------

Bullae with the cleavage plane above the basal layer of the epidermis suggests pemphigus vulgaris, which is caused by autoantibodies to intercellular junctions of epidermal cells. The autoantibodies decrease the ability of the keratinocytes to adhere to one another, permitting formation of vesicles and bullae. Oral involvement is common, and often precedes the characteristic skin lesions. Separation of the epidermis upon manual stroking of the skin is known as Nikolsky's sign. This sign is present in other disorders such as Stevens-Johnson syndrome, but we are told the woman is not taking any medications, a typical cause of Stevens-Johnson syndrome in the adult population. Antibodies to epidermal basement membrane proteins (choice A) are seen in bullous pemphigoid, which is a bullous disease characterized by blisters with a cleavage line between the epidermis and dermis. Antibodies to glycoprotein IIb/IIIa (choice B) are seen in autoimmune thrombocytopenic purpura. Antibodies to intrinsic factor (choice D) are seen in pernicious anemia. Antibodies to Type IV collagen (choice E) are seen in Goodpasture's syndrome

This patient most likely has subacute granulomatous (de Quervain's) thyroiditis, which frequently develops after a viral infection. Microscopically, it is characterized by microabscess formation within the thyroid, eventually progressing to granulomatous inflammation with multinucleated giant cells. Clinically, patients may experience fever, sudden painful enlargement of the thyroid, and/or symptoms of transient hyperthyroidism. The disease usually abates within 6 to 8 weeks. Diffuse nontoxic goiter (choice A) by definition does not produce hyperthyroidism. The hyperthyroidism of Graves disease (choice B) does not spontaneously remit.
Hashimoto's thyroiditis (choice C) can cause transient hyperthyroidism, but then goes on to cause hypothyroidism. Subacute lymphocytic thyroiditis (choice E) can cause transient hyperthyroidism, but is characteristically painless.

In social learning, also known as modeling, behavior is acquired by watching other persons and assimilating their actions into the behavioral repertoire. There is no verbal or cognitive process (choice B) that is involved, no reinforcement (as in operant conditioning; choice D), no pairing of stimuli to get stimulus substitution (as in classical conditioning; choice A), nor any early-life bonding or imprinting (choice C) involved in this type of process. Because behaviors such as spousal abuse, child abuse, and elder abuse are all based on observing and incorporating behaviors from significant others, the person displaying the behaviors does not realize the behaviors are inappropriate and is typically very resistant to change. The fact that the learning is nonverbal and not dependent upon reinforcement contributes to the resistance to change.

The patient is presenting with signs and symptoms of acute cholecystitis, which is associated with gallstones in more than 90% of all cases. This condition occurs when a stone becomes impacted in the cystic duct and inflammation develops behind the obstruction. The acute attack is often precipitated by a large fatty meal, and is characterized by the sudden appearance of severe, steady pain localized to the epigastrium or right hypochondrium. Laboratory findings often include elevated white blood cells (2,000 - 15,000/mL). Total serum bilirubin values of 1-4 mg/dL may be seen in some instances, and serum amylase may be elevated. In noncomplicated cases, treatment often includes IV alimentation, analgesics, and antibiotics, as well as withholding of oral feedings. Meperidine is the narcotic of choice since it is least likely to cause spasm of the sphincter of Oddi, probably because of its antimuscarinic properties. It is therefore preferred over morphine (choice B), oxycodone (choice D), and propoxyphene (choice E). Furthermore, propoxyphene is a narcotic agonist with mild analgesic properties; hence, it would most likely not be able to effectively treat this patient's severe pain. Naproxen (choice C) is a nonsteroidal anti-inflammatory drug (NSAID) indicated for the treatment of mild to moderate pain; this agent would most likely not provide sufficient pain control for this patient.

Hypersecretion of insulin by a pancreatic b cell tumor is a major cause of fasting hypoglycemia (plasma glucose is not increased, choice D). Symptoms are related to neuroglycopenia and could include recurrent central nervous system dysfunction during fasting or exercise. While proinsulin only makes up approximately 20% of plasma immunoreactive insulin in normal individuals, in patients with an insulinoma it contributes 30-90% of the immunoreactive insulin. Hence, plasma levels of proinsulin are increased. The increased secretion of insulin by the tumor will also lead to an increase in C peptide secretion (not decreased, choice B) since b cells secrete insulin and C peptide on a one-to-one molar ratio. Given the prolonged hypoglycemia, the amount of glycosylated hemoglobin may also be decreased, although this is not a universal finding. Certainly, an increase in glycosylated hemoglobin would not be expected (choice A). Glucagon secretion is increased by hypoglycemia and its plasma level in a patient with an insulinoma would be expected to be increased compared to normal (not decreased, choice C

The disease is Duchenne muscular dystrophy, an X-linked recessive muscular disease usually caused by a deletion involving the dystrophin gene. This defect produces accelerated muscle breakdown leading initially to proximal muscle weakness, then later to generalized weakness that typically begins before age 5. A feature of X-linked recessive diseases is that carrier mothers pass the disease to half their sons; affected fathers can have carrier daughters but not affected sons. Since the mother is presumably normal (because the disease is X-linked), she must be a carrier to have an affected son, and the grandmother must also be a carrier, therefore the mother's brother (maternal uncle) may also have the disease. The father's (choice A) side of the family, including the father's brother (choice B), most likely does not carry the defective gene (since they themselves would be affected, and furthermore since the father cannot pass the gene on to a son). It would be extremely unlikely for a carrier female to marry an affected male (and the question does not mention any similar symptoms in the father). The mother (choice C) and possibly the sister (choice E) are carriers of, but not affected by, the defective gene.

This is a classic presentation of a patient with carpal tunnel syndrome, which typically affects females between the ages of 40 and 60 who chronically perform repetitive tasks that involve movement of the structures that pass through the carpal tunnel. One important structure that passes through the carpal tunnel is the median nerve. Patients often note a tingling, a loss of sensation, or diminished sensation in the digits. There is also often a loss of coordination and strength in the thumb, because the median nerve also sends fibers to the abductor pollicis brevis, flexor pollicis brevis, and the opponens pollicis. A final function of the median nerve distal to the carpal tunnel is control of the first and second lumbricals which function to flex digits two and three at the metacarpophalangeal joints and extend interphalangeal joints of the same digits. Abduction of the fifth digit (choice A) is a function controlled by the ulnar nerve, which does not pass through the carpal tunnel. Adduction of the thumb (choice B) is a function of the adductor pollicis, which is the only short thumb muscle that is not innervated by the median nerve, but rather by the deep branch of the ulnar nerve. Sensation of the lateral half of the dorsum of the hand (choice D) is mediated by the radial nerve, which also does not pass through the carpal tunnel. Sensation over the lateral aspect of the palm (choice E) is mediated by the median nerve, however the branch
innervating the palm (palmar cutaneous branch of the median nerve) passes superficial to the carpal tunnel. Sensation over the medial aspect of the dorsum of the hand (choice F) is mediated by the ulnar nerve. Sensation over the medial aspect of the palm (choice G) is mediated by the ulnar nerve.

Chronic lymphocytic leukemia (CLL) is typically a disease of the elderly, with 90% of cases occurring after the age of 50; the median age is 65. Patients will typically present with a complaint of chronic fatigue and/or lymphadenopathy. Approximately 50% of all patients with CLL present with an enlarged liver and/or spleen. CLL typically pursues an indolent course but can occasionally present as a rapidly progressive disease. The hallmark of CLL is the isolated lymphocytosis in which the white blood cell count is usually greater than 20,000/mL and between 75% and 98% of the circulating cells are small "mature" lymphocytes. Chlorambucil is classified as a nitrogen mustard, a subcategory of the alkylating agents. It is primarily used to treat chronic lymphocytic leukemia and ovarian carcinoma; it can also be used to treat Hodgkin's disease and various other lymphomas. Cisplatin (choice B) is an alkylating agent indicated for the treatment of metastatic testicular and ovarian tumors in combination with other agents. Dacarbazine (choice C) is a cytotoxic agent with alkylating properties. It is used as a single agent or in combination with other antineoplastics in the treatment of metastatic malignant melanoma, refractory Hodgkin's disease, and various sarcomas. Tamoxifen (choice D) is an antiestrogen hormone used in the palliative treatment of breast cancer in patients with estrogen-receptor-positive breast cancer. Vinblastine (choice E) is a mitotic inhibitor antineoplastic agent indicated for the treatment of Hodgkin's disease and non-Hodgkin's lymphomas, choriocarcinoma, lymphosarcoma, and neuroblastoma, as well as various other types of cancer.

Urticaria (hives) are pruritic wheals that form after mast cells degranulate and trigger localized dermal edema with dilated superficial lymphatic channels. The mast cell degranulation is sometimes, but not always, triggered by IgE-antigen interactions. Granular complement and IgG deposition at the dermal/epidermal junction (choice B) is a characteristic of systemic lupus erythematosus. Microscopic blisters (choice C) are a characteristic of dermatitis herpetiformis. Munro abscesses (choice D) are a characteristic of psoriasis.Solar elastosis (choice E) is found in actinic keratoses.

The innervation of the tongue is complex. The mandibular division of the trigeminal nerve (V3) carries general somatic sensation from the anterior two-thirds of the tongue. The maxillary division (V2, choice A) carries somatic sensation from the palate, upper gums, and upper lip. The facial nerve (VII, choice C) carries taste from the anterior two-thirds of the tongue. The glossopharyngeal nerve (IX, choice D) carries sensation and taste from the posterior one-third of the tongue. The vagus nerve (X, choice E) carries sensation from the lower pharynx.

One of the most common side effects of any antineoplastic therapy is weight loss secondary to decreased appetite and/or nausea and vomiting. Furthermore, weight loss due to decreased food intake tends to occur more frequently in elderly patients receiving antineoplastic therapy. One medication that has consistently helped to increase appetite in such patients is megestrol acetate. This agent is a progestational hormone with antineoplastic properties used in the treatment of advanced carcinoma of the breast and endometrium. Megestrol, when given in relatively high doses, can substantially increase the appetite in most individuals, even those with advanced cancer. Amitriptyline (choice A) is a tricyclic antidepressant used in the treatment of depression. There is nothing mentioned in the case study to suggest that the patient is clinically depressed; hence, this agent would provide no benefit. Methotrexate (choice C) is an antimetabolite and folic acid antagonist commonly used in various neoplastic disorders and in the treatment of rheumatoid arthritis. Since nausea, vomiting, and ulcerative stomatitis are common side effects of this medication, its usage in this patient would not be recommended. Neostigmine (choice D) is a carbamylating acetylcholinesterase inhibitor that would not increase appetite. Prochlorperazine (choice E) is a phenothiazine derivative used primarily to control severe nausea and vomiting. This patient is not experiencing nausea. Furthermore, this agent does not possess appetite-stimulating properties

The mediastinum is divided into four regions. The region above the manubriosternal junction (level of fourth thoracic vertebra) is the superior mediastinum. The region below the manubriosternal junction is divided into the anterior mediastinum (anterior to the pericardium), the middle mediastinum (within the pericardium), and the posterior mediastinum (posterior to the pericardium). The thoracic duct enters the thorax through the aortic hiatus of the diaphragm. At this point it lies in the posterior mediastinum, the region posterior to the pericardium. As it ascends through the thorax and passes the level of the fourth thoracic vertebra, it enters the superior mediastinum. The anterior mediastinum (choices A and B) contains the thymus and fatty connective tissue. The middle mediastinum (choices A, C, and D) contains the heart and the roots of the great vessels. In addition to the thoracic duct, the superior mediastinum (choices B, D, and E) contains the ascending aorta, aortic arch, branches of the aortic arch, descending aorta, superior vena cava, brachiocephalic veins, thymus, trachea and esophagus. In addition to the thoracic duct, the posterior mediastinum (choices C and E) contains the descending aorta, azygos vein, hemiazygos vein and the esophagus

Warfarin is the oral anticoagulant the patient was most likely taking. This drug is commonly prescribed to patients with atrial fibrillation to prevent the formation of atrial thrombi. Warfarin increases prothrombin time (PT) because it interferes with the synthesis of the vitamin K clotting factors of the liver (II, VII, IX, and X) and therefore necessitates regular monitoring of the PT. Cimetidine is an H2-blocker that inhibits hepatic enzymes, including those that metabolize warfarin. Consequently, coadministration of warfarin and cimetidine results in enhanced warfarin activity, producing pronounced anticoagulation and the bleeding diathesis in the patient in question. Cimetidine has one of the worst side effect profiles of all the H2-blockers and may also result in gynecomastia in men. Famotidine (choice B) is an H2-blocker that does not affect liver metabolism. Misoprostol (choice C) is a prostaglandin E1 analog used in peptic ulcer disease. It does not affect hepatic metabolism. Omeprazole (choice D) is a proton-pump inhibitor used to decrease acid production in patients with peptic ulcer disease or reflux. It does not affect drug metabolism by the liver. Ranitidine (choice E) is another H2-blocker. It does not inhibit liver enzymes as strongly as cimetidine does.

Specificity refers to how well a test identifies persons who do not have the disease in question. In the example, 2900 women do not have breast cancer, and 2540 of these women have a negative test. Specificity is given by (true negatives)/ (true negatives + false positives) = 2540/(2540+360) = 2540/2900. Choice A, 90/100, represents the sensitivity of the test; that is, the proportion of women with the condition who test positive. Choice B, 90/450, gives the predictive value of a positive test. Of the 450 women who tested positive, 90 actually had the condition. Choice C, 2540/2550, gives the predictive value of a negative test. Of the 2550 who tested negative, 2540 did not have cancer. Choice E, (90+2540)/3000, refers to the efficiency of a test; that is, the proportion of all subjects who were correctly classified by the test.

Familial hypercholesterolemia, which is due to defective function of the LDL receptor, is an area of intense research. The molecular basis of LDL receptor abnormalities is becoming better understood, and more than 200 mutations in the gene for the LDL receptor have been identified. The gene has 5 general domains and 18 exons. Defects near exons 7 to 14 (including this case) are in the region of homology with epidermal growth factor receptor precursor. This region of the molecule is needed for dissociation of LDL from the receptor in the endosome. Receptors with a defect in this area (sometimes called class II mutations) also have trouble being initially transported to the Golgi complex (transport-deficiency alleles) and become trapped in endoplasmic reticulum. Decreased transcription of the LDL receptor gene (choice A) is considered a class I mutation and involves the signal sequence domain near exon 1. Poor internalization of LDL bound to LDL receptor (choice B) is considered a class IV mutation. Such mutations are associated with the membrane-spanning/cytoplasmic domain, specifically near exon 18.Poor retention of the LDL receptor in the membrane (choice C) is considered a class IV mutation and is associated with the membrane-spanning/cytoplasmic domain, specifically near exons 2-6. Reduced binding of LDL (choice D) is considered a class III mutation and involves the LDL binding domain near exons 2-6.

Most of the venous drainage of the skin of the lower extremity is to the long saphenous vein, the accompanying lymphatics of which drain into the superficial group of the inguinal lymph nodes. However, the skin drained by the short saphenous vein, including that of the lateral aspect of the dorsum of the foot, is an exception to this rule. Lymphatic fluid from this area drains into lymphatics accompanying the short saphenous vein, then drains into lymph nodes behind the knee in the popliteal fossa. The lateral side of the thigh (choice B), the medial side of the leg below the knee (choice C), the medial side of the sole of the foot (choice D), and the medial side of the thigh (choice E) all drain to the superficial inguinal nodes.

The probable location of lesions producing visual defects is a favorite USMLE topic (and is also well worth knowing if you have occasion to work up such a patient). Here is a list that may help you sort through
these problems: Central scotoma ~ macula Ipsilateral blindness ~ optic nerve Bitemporal hemianopia ~ optic chiasm (choice B) Homonymous hemianopia ~ optic tract (choice E) Upper homonymous quadrantanopia ~ temporal optic radiations (choice D) Lower homonymous quadrantanopia ~ parietal optic radiations (choice C) Also, cortical lesions produce defects similar to those of the optic radiations, but may spare the macula.

Sucralfate is a promising drug that is not presently in widespread use because it is incompatible with H2 antagonists such as cimetidine, ranitidine, famotidine and nizatidine. Sucralfate is aluminum sucrose sulfate, a sulfated disaccharide, which polymerizes and binds to ulcerated tissue. It forms a protective coating against acid, pepsin and bile, giving the tissue a chance to heal. Unfortunately, a low gastric pH is required for polymerization, meaning that sucralfate is incompatible with drugs that reduce gastric acidity, such as H2 blockers and antacids. The moral of the story is that you cannot assume that two medications that are individually helpful in a medical condition will be synergistic. Learning the mechanisms by which the drugs work will help you spot potential interactions and earn you points on the USMLE.

The description is that of gonadal dysgenesis. In the absence of testosterone, the Wolffian ducts will regress and fail to differentiate into normal male internal reproductive tracts. In the absence of Müllerian regression factor, the Müllerian ducts will automatically differentiate into oviducts and a uterus. Differentiation of the male external genitals is dependent on adequate dihydrotestosterone (via an action of 5 a-reductase on testosterone). In the absence of testosterone, female-type external genitalia will develop. Selective dysgenesis of the Sertoli cells could produce the situation described in choice A. Normal Leydig cells would secrete testosterone and produce normal male-type internal and external tracts. However, the absence of Müllerian regression factor, which is secreted by the Sertoli cells, would allow formation of female-type internal structures as well. Female-type internal reproductive tract and male-type external genitalia (choice C) would not be likely to occur under any circumstances. The situation described in choice D could occur with 5 a-reductase deficiency. Normal male-type internal tracts can form because there is no requirement for dihydrotestosterone. Müllerian regression factor will prevent differentiation of female-type internal tracts. Since differentiation of the normal male external genitals requires dihydrotestosterone, 5 a-reductase deficiency will lead to feminization. The situation described in choice E is normal, and would not occur in the individual described who has testicular dysgenesis.

A direct inguinal hernia occurs when abdominal contents herniate through a weak spot in the abdominal wall within Hesselbach's triangle. This type of hernia passes medial to the inferior epigastric artery, which differentiates it from an indirect inguinal hernia that passes lateral to the artery and through the deep inguinal ring. Direct inguinal hernias do not pass through the deep inguinal ring and are not covered by all three layers of the spermatic fascia. The lateral border of the rectus abdominis muscle is a boundary of Hesselbach's triangle, but the hernia does not pass medial to it. It also does not pass posterior to the inguinal ligament.

95% of a normally distributed population will fall between plus or minus 1.96 standard deviations from the mean. Since the population is normally distributed with regard to IQ, this means that approximately 2.5% of the population will have IQ scores 2 standard deviations or more above the mean, and 2.5% of the population will have IQ scores 2 standard deviations or more below the mean. 2.5% of 200 people is 5 people

Mastication is a complex process involving alternating elevation, depression, forward movement, and backward movement of the lower jaw. The backward movement step is accomplished by the posterior fibers of the temporalis muscle. The digastric (choice A) helps to depress the lower jaw during chewing.
The lateral pterygoid (choice B) helps to move the lower jaw forward during chewing. The medial pterygoid (choice C) helps to elevate the lower jaw during chewing. The mylohyoid (choice D) helps to depress the lower jaw during chewing.

The pituitary gland is located in the pituitary fossa within the skull. The floor of this fossa is formed by the sella turcica. The lateral walls of the fossa are formed by the cavernous sinuses. The abducens nerve passes through the cavernous sinus along with the internal carotid artery. As the tumor expands laterally, the first nerve that will be encountered is the abducens nerve, producing a lateral rectus palsy. The oculomotor nerve (choice B) lies in the lateral wall of the cavernous sinus. It is further from the pituitary gland than is the abducens nerve. The optic nerve (choice C) is anterosuperior to the pituitary gland. Upward expansion of the tumor may compress the optic chiasm. The trigeminal nerve (choice D) is found posterior to the cavernous sinus. Two of its three divisions (ophthalmic and maxillary divisions) pass through the lateral wall of the cavernous sinus and are further from the pituitary gland than is the abducens nerve. The trochlear nerve (choice E) is also in the lateral wall of the cavernous sinus, and would be affected later if the tumor continued to expand.

The child has "rat-bite fever." This occurs in two forms with somewhat similar clinical manifestations. The form this child has is the Haverhill fever form, caused by Streptobacillus moniliformis and characterized by a short (often 1-3 days) incubation period. The Haverhill form is more common in the United States than the Sodoku form, which is caused by Spirillium minus, has a 1-4 week incubation period, and is most prevalent in Japan. One of the problems with diagnosing these diseases is that the victims are usually young children, and the bite site may be inapparent by the time the disease becomes severe enough for the child to be taken to a doctor. Borrelia burgdorferi (choice A) causes Lyme disease, which is characterized by an expanding erythematous rash, arthralgias, and eventual nervous system involvement. Pseudomonas mallei (choice B) causes glanders, which generally affects horses or humans in close contact with equines. Pseudomonas pseudomallei (choice C) causes melioidosis, a rare pulmonary disease found mostly in Southeast Asia. Spirillium minus (choice D) causes the Sodoku form of rat-bite fever.

The patient has I-cell disease, also known as mucolipidosis II, which is due to a defective UDP-N-acetylglucosamine-1-phosphotransferase, the enzyme that phosphorylates mannose on enzymes destined for lysosomes. Proteins coded by nuclear DNA are synthesized on cytoplasmic ribosomes, which may be either "free" or associated with the endoplasmic reticulum to form the rough endoplastic reticulum (RER). Proteins synthesized on the RER are transferred into the Golgi apparatus, where they undergo further modifications that determine whether they remain part of the Golgi apparatus, become part of the plasma membrane, or are shipped to lysosomes or mitochondria. Proteins not marked for transport to a specific intracellular site follow the default pathway and are exported into the extracellular compartment. The signal for transport of the acid hydrolases (and probably other enzymes) to the lysosomes is phosphorylation of a terminal mannose moiety on an N-linked oligosaccharide to form mannose 6-phosphate. In I-cell disease, this terminal mannose moiety is not phosphorylated, and the acid hydrolases follow the default pathway and are secreted. Deficiency of alpha-L-iduronidase results in lysosomal accumulation of dermatan sulfate and heparan sulfate (choice A) in several conditions such as mucopolysaccharidosis I, Hurler's disease, or Hurler's/Scheie disease. Hexosaminidase A deficiency (Tay-Sachs disease) is one example of a condition in which ganglioside accumulation occurs (choice B). There are a number of diseases in which glycogen degradation (choice C) is defective. These are collectively termed glycogen storage diseases since they result in abnormal cellular accumulation of glycogen. In Pompe's disease, or type
II glycogen storage disease, a lysosomal glucosidase is deficient, resulting in lysosomal glycogen accumulation. Deficiency of sphingomyelinase (choice D), an enzyme involved in degradation of sphingomyelin, results in Niemann-Pick disease. Phosphorylation of tyrosine moieties (choice F) is unrelated to lysosomes or lysosomal enzymes; however, decreased ability to phosphorylate tyrosine moieties might be associated with diabetes or dwarfism.