USMLE-STEP-2 Online Practice Questions and Answers

Correct Answer: D

This is an autosomal dominant disorder. Both parents are carriers of the abnormal gene (N), which is on chromosome 17. If each parent is a heterozygote (Nn, where n is the normal gene), 25% of their offspring will have a normal genotype, nn. Fifty percent of their offspring will be affected heterozygotes (Nn), and the remaining 25% will be homozygous affected (NN). If either parent or both are homozygous for the abnormal gene (NN), 100% of the offspring will be affected. As an autosomal disorder, there is no sex predilection; males and females are affected with equal frequency. Prenatal diagnosis is available.

Correct Answer: E

Organic acids produced by bacterial fermentation lower the pH of dental plaque causing demineralization and caries of the adjacent tooth. Nursing bottle caries is a pattern of caries involving the upper and lower incisors. It occurs because of prolonged contact of the tooth to a sugar-containing liquid (juice or milk). This is more likely to occur with overnight exposure or with use of a bottle. Asimilar pattern of caries may rarely occur with breast-fed babies who feed through the night. Cup feeding or drinks given during mealtimes are less likely to cause prolonged contact to the teeth.

Correct Answer: E

The most common causes of neonatal cholestasis are extrahepatic biliary atresia and idiopathic neonatal hepatitis. Infants usually develop icterus by 26 weeks of age. They have conjugated hyperbilirubinemia, dark urine, and acholic stools. At time of presentation, there is usually hepatomegaly, as well as pruritis, splenomegaly, and ascites. The use of RhoGAM (anti-D gamma globulin) has reduced the incidence of Rh sensitization and resulting jaundice. ABO incompatibility can also cause a milder form of isoimmune hemolytic disease and jaundice. It is more common in infants with blood types Aand B born to mothers with blood type O. Anemia is usually present; direct Coombs test is weakly positive; and indirect Coombs test is positive. Crigler-Najjar syndrome is autosomal recessive; there is usually marked hyperbilirubinemia (240 mg/dL) in an otherwise asymptomatic infant. The high levels result in kernicterus. Physiologic jaundice is the most common cause of unconjugated hyperbilirubinemia; it is characterized by peak bilirubin level of <13 mg/dL on day of life 35, decrease to normal within 2 weeks. In breast-fed infants, this is often exaggerated, with levels >13 mg/dL. This occurs in 1025% of breastfed infants, as opposed to 47% of formulafed infants. It is known as "breast-feeding" jaundice. "Breast-milk" jaundice, develops after the first week of life, peaking between the 2nd and 3rd week to 1020 mg/dL. The cause of this has not been established.

Correct Answer: B

IG given before exposure or within 14 days of exposure is 7585% effective in preventing symptomatic illness from hepatitis A. IG is produced from the plasma of normal adults and does not contain sufficient antibody to prevent hepatitis B infection. Hepatitis B immune globulin (HBIG) is prepared from plasma known to contain high antibody titers for hepatitis B surface antigen (HBsAg) and is specific for hepatitis B. Given immediately postexposure, and again 1 month later, it has a combined efficacy of about 75% in the prevention of hepatitis B. Postexposure IG has not been found effective in the prevention of hepatitis C infection; on the other hand, treatment of early hepatitis C infection is possible, and thus it is important to monitor exposed individuals to determine whether infection occurs. IG administered to individuals exposed to measles infection who are susceptible to the disease has been shown to be effective if given within 6 days of exposure.

Recent use of IG is a contraindication to immunization with rubella vaccine. IG is not very effective at preventing in utero infection with rubella, and infants with congenital rubella syndrome have been born to women given IG shortly after exposure. IG is not routinely indicated, as it is indicated only if abortion is not elected.

Correct Answer: A

The Behavioral Risk Factor Surveillance System is a health survey that uses telephone interviews to collect information about chronic disease risk factors such as obesity, treatment for blood pressure, alcohol use, and exercise. Review of hospital records may capture some of this information, but is not an efficient method of capturing information on multiple risk factors for chronic disease. Registries are primarily used to track clinical information regarding particular diseases or conditions. They do not tend to capture a large body of information on behavioral risk factors. Physician-based reports are usually generated as a consequence of state or federal mandates regarding the reporting of communicable disease, rather than behavioral risk factors for chronic disease.

Correct Answer: B

Complaints involving both psychological and medical conditions are difficult to diagnose and treat. At times, medically identifiable causes are present, but the psychological factors contributing to the discomfort complicate the diagnosis and treatment and lead to frustration in both physician and patient. At other times, no identifiable cause for pain or other physical symptoms can be found; nevertheless, the patient still has the symptoms. Questions arise:

Is the patient lying? Is there some deep psychological problem? Could there be a medical disorder in the early stages of development that gives rise to physical symptoms but no clear physical signs to make the diagnosis? One group of psychiatric disorders addresses some of these issues--the somatoform disorders. Somatization disorder is an axis I psychiatric disorder where a patient complains of multiple somatic complaints involving multiple organ systems, but which cannot be explained by physical and/or laboratory findings. Conversion disorder is another axis I disorder where there is a disturbance of bodily function that does not conform to anatomic or neurologic concepts, and it is due to psychological factors. Body dysmorphic disorder is a pervasive subjective feeling/belief that some aspect of the patient's appearance is ugly or deformed. Hypochondriasis is a persistent belief in the presence of one or two serious physical diseases despite medical assurance that one does not have the disease/illness. Pain disorder (somatoform pain disorder) is a disorder with the presence of severe, distressing and persistent pain which cannot be explained adequately by evidence of a physiologic process or physical disorder. Panic disorder is a kind of anxiety disorder. Discrete periods of extreme sympathetic nervous system symptoms occur, including tachycardia, sweating, shortness of breath, and others, during which time a person experiences extreme fear. Malingering is the deliberate manufacture of false or exaggerated symptoms for financial gain or to avoid an unpleasant situation such as jail time or military duty. In a factitious disorder, there is the deliberate production of signs and symptoms of illness in order to assume the sick role.

Correct Answer: E

Generally speaking, anorexic patients who are 20% or more below their expected weight for their height are recommended for inpatient programs. Inpatient programs for anorexia nervosa usually use a combination of a behavioral management approach, individual psychotherapy, family education and therapy, and in some cases psychotropic medications.

Correct Answer: D

Though Alzheimer's dementia is the most common form, it is characterized by a gradual and progressive course typically starting with a loss of short-term memory. Vascular dementia is known for its stepwise progression. Frontotemporal dementia (Pick's) usually presents insidiously with behavior and personality changes. Lewy body dementia shares features with Alzheimer's dementia and dementia associated with Parkinson's disease, but is more progressive than the dementia associated with Parkinson's disease, and tends to exhibit cognitive decline soon after the Parkinson's symptoms present. Visual hallucinations and fluctuating cognition are also common with this type of dementia

Correct Answer: B

Infants with pyloric stenosis usually present after the third week of life with symptoms of progressive pyloric outlet obstruction secondary to increasing hypertrophy of the pyloric muscle. There are often clinical signs of dehydration, but the infant usually appears well and is eager to feed. Viral gastroenteritis and urinary tract sepsis may be associated with signs of such systemic illness as lethargy, poor feeding, and, in some cases, fever. Gastroesophageal reflux more typically presents with a history of regurgitation since birth. Milk protein allergy is often associated with colicky abdominal pain and diarrhea. The pathognomonic sign on clinical examination is a palpable "olive" in the epigastrium or right upper quadrant. Abdominal ultrasound is operator dependent, but with expertise in interpretation of the study, the thickened elongated pyloric channel can be demonstrated. AUGI contrast study may show the classic "shouldering" of the pyloric muscle, with a "string sign"; this also requires expertise in performing the examination, and other causes of pyloric outlet obstruction, such as pylorospasm may be misinterpreted as a positive study. Surgical exploration should be reserved for those patients in whom the diagnosis has been confirmed and only after the infant has received fluid resuscitation. Infants with gastric outlet obstruction develop a hypochloremic, hypokalemic metabolic alkalosis. This is secondary to the loss of chloride in the gastric contents, and the renal reabsorption of sodium in exchange for potassium and hydrogen. Carbonic anhydrase converts carbonic acid to hydrogen and bicarbonate ions, allowing hydrogen to be excreted in the urine, with retention of the bicarbonate. Hence, with the metabolic alkalosis, there is a "paradoxical aciduria." Hypernatremic, hyperchloremic, hypokalemic metabolic acidosis develops in infants with diarrhea. Infants with gastroesophageal reflux do not usually develop significant electrolyte derangements. Infants with pyloric stenosis will usually require a period offluid resuscitation to correct hypovolemia as well as electrolyte and acid-base abnormalities.

This is followed by a pyloromyotomy. Infants with vomiting and diarrhea from viral gastroenteritis are often successfully managed with oral rehydration. Prokinetic agents have been used in the management of gastroesophageal reflux. Soy formulas or elemental formulas are recommended for the infant with a milk protein allergy

Correct Answer: A

Ciprofloxacin is the drug of choice in a dose of 500 mg bid for 13 days because most cases of travelers' diarrhea are from E. coli. This patient's symptoms are moderate to severe and warrant antibiotic treatment which will decrease the frequency of bowel movements and duration of illness. Erythromycin and tetracycline are effective for Vibrio which is an uncommon cause of travelers' diarrhea. Metronidazole is used for Clostridium difficile enteritis.