USMLE-STEP-2 Online Practice Questions and Answers

Correct Answer: D

Deficiency of dopamine primarily is responsible for the signs and symptoms of Parkinson's disease. Specifically, the loss of dopamine from the substantia nigra is thought to be primarily responsible for the akinesia and rigidity. Tremor, akinesia, and rigidity are the classic triad of signs seen in Parkinson's disease. The tremor typically is a resting tremor; often a "pill rolling" tremor is seen in the hand. Well over 90% of patients with Parkinson's disease do have a good initial response to levodopa

Correct Answer: C

All of the drugs used to treat hypertension can cause adverse reactions, ranging from trivial to life threatening. Thiazide diuretics are associated with hypokalemia, causing arrhythmias; hyperuricemia causing gout; and hyperglycemia due to insulin resistance. The vasodilator hydralazine can cause tachycardia with increased angina and a lupuslike syndrome. As many as 10% of patients on angiotensinconverting enzyme (ACE) inhibitors develop an annoying dry cough. Because they block aldosterone, they can lead to hyperkalemia. ACE inhibitors cause 1025% of all cases of angioedema. Peripheral edema is the most commonly reported side effect of calcium channel blockers, especially amlodipine and nifedipine. Constipation, flushing, and dizziness are also frequently reported. Coombs'-positive hemolytic anemia and hepatitis are idiosyncratic reactions to the central adrenergic-stimulant methyldopa.

Correct Answer: D

Breast development in an infant or young child is the consequence of increased estrogen secretion, exposure to exogenous estrogens, or increased response of breast tissue to normal, prepubertal amounts of estrogen. After excluding exposure to exogenous estrogens (e.g., OCs, estrogen creams), increased response to estrogen is more common than increased estrogen secretion from the ovaries or adrenal glands when breast development is the only sign of precocious puberty. The uterus and adnexa can be palpated abdominally in prepubertal girls if they are pathologically enlarged. For this reason, an estrogen-secreting ovarian tumor (granulosa cell is the most common type) is usually palpable, and an ultrasound examination is unnecessary. For the same reason, a pelvic examination under anesthesia is not necessary, especially if the serum estradiol concentration is normal. CT scan of the head and a serum FSH concentration are unnecessary if breast development is the only sign of precocious puberty, and the serum estradiol concentration is normal in the prepubertal range.

Correct Answer: B

Bubonic plague is uncommon in the United States. It is almost always contracted through a bite by an infected flea. Asmall local papule or vesicle, and sometimes a local ulceration, may occur at the site of the

Y. pestis infecting bite. Mucous membranes and broken skin also can be entry sites. After an incubation period of 26 days, illness is manifested by fever, chills, headache, myalgia, and arthralgia. Eventually, there is painful enlargement (the bubo) of lymph nodes draining the inoculation site.

Correct Answer: A

Giardiasis may cause cramping and a chronic diarrheal syndrome, with malabsorption and weight loss. Its distribution is worldwide, particularly where hygienic standards are not high. It also occurs sporadically in high-risk individuals. Streptococcal pyoderma, including erysipelas and impetigo, has been demonstrated to precede acute glomerulonephritis. Even when appropriate antibiotics are given in adequate dosage and duration for these conditions, renal damage may still result. Prevention thus consists of wound care, including cleaning wounds well and removal of crust. Mycoplasma infections are particularly common in families with younger children. They are frequently imported to the family by school-aged children, leading to a low-grade fever and persisting tracheobronchitis in the parents, or more acutely, an atypical pneumonia. G. lamblia is found in up to 20% of homosexual males, and may cause chronic diarrhea, although in these patients it tends to be asymptomatic. E. coli was first reported as a cause of watery diarrhea in nurseries in the 1940s. Although nursery epidemics with enteropathogenic serotypes had decreased in recent years in the United States, the increase of infant- child day care centers has resulted in their relatively frequent occurrence. Furunculosis is most frequently caused by coagulase-positive staphylococcal infections. The public health significance of this largely relates to the hazards of skin infections in food handlers and subsequent staphylococcal toxin in the food, leading to staphylococcal intoxication food-borne disease. H. pylori has been associated with gastric ulcers, but not with duodenal ulcers. Otitis media, whether acute or with effusion, commonly results from viral infection, such as by RSV. Various other organisms may be responsible including Streptococcu pneumoniae, H. influenzae, and others. C. perfringens, with rare exceptions, is transmitted in a meat dish prepared in bulk. Under propitious circumstances for the organism, especially on cooling of the food, bacterial multiplication can be very rapid. Symptoms begin to occur in the affected population in about 12 hours. Epidemic typhus is a rickettsial illness. Man is the host and long-term reservoir. The vectors are body lice (P. humanus corporis). The rickettsia are not present in human excretions and cannot be transmitted by person-toperson contact.

Correct Answer: E

The insurance company charges premiums to the employer based on "experience rating," which means charges are based on past utilization of service. To control premiums in the future, control utilization now. Community rating would be different, in that risk would be spread across a broader community. Community rating makes insurance more affordable for individuals or groups that use a lot of health care, but removes incentive to control costs.

Correct Answer: C

Active surveillance is used in urgent situations, such as active and ongoing epidemics. Health agencies contact those data sources most likely to have current information regarding cases. The collection of data which has been voluntarily submitted is referred to as passive surveillance. Case-control studies are a form of investigation and represent a "next step" after surveillance. These studies seek to identify further information regarding the health problem y studying individuals with the disease. Surveillance systems on the other hand are used primarily to identify whether or not a problem exists and how it is changing through time. Monitoring disease in animal population or in other specific populations that are higher or earlier risk is referred to as sentinel data collection or surveillance. Identifying where cattle were purchased may help to identify the extent of disease spread in animals, but does not describe active surveillance of human cases.

Correct Answer: D

This infant has an omphalocele. This is a result of failure of the abdominal muscles to close in the midline at the umbilical cord. The abdominal wall defect is therefore midline, with viscera enclosed in a sac composed of amniotic membranes. Children with omphalocele may have other associated anomalies. Infants with abdominal wall defects are at risk for fluid and temperature loss, and infection. Therefore, the initial management consists of measures to decompress the gastrointestinal tract, fluid resuscitation, IV antibiotics, and placing the viscera in a warm, moist occlusive dressing. An umbilical hernia results when the umbilical ring does not close, with viscera enclosed in a sac covered by peritoneum and skin. Many of these may spontaneously close on their own. Therefore, surgical intervention is restricted to those children with a persistent fascial defect. Omphalitis results from bacterial infection at the base of the cord and is well treated with antibiotics to cover skin organisms. Gastroschisis is a congenital evisceration, located to the right of the umbilical cord, and thought to be related to obliteration of one of the umbilical veins prior to birth. As with omphalocele, the child needs NG decompression, IV fluids and antibiotics, and a warm moist occlusive dressing. In gastroschisis, the bowel may be at risk of mechanical or vascular compromise, thus urgent surgical intervention is required

Correct Answer: C

Asthma is characterized by bronchospasm and typically causes a prolonged expiratory phase and retention of carbon dioxide. This degree of hypoxia (PO2 of 49) generally would not be seen with asthma. Pulmonary embolism, congestive heart failure, myocardial infarction, or pneumonia all could lead to this degree of hypoxia. The constellation of fever, elevated white count, and localized infiltrate on CXR is most characteristic of pneumonia. The most likely etiology is perioperative aspiration related to general anesthesia.

Correct Answer: C

The CDC has identified lead poisoning as one of the most common and preventable childhood health problems in the United States. Recent data indicate that undesirable behavioral and cognitive deficits can occur at levels previously thought to be "safe." Screening all children aged 672 months, by questionnaire or blood-lead level, is suggested. Children at greatest risk for lead poisoning include young inner-city children who live in housing constructed before 1960; children living near lead processing smelters, battery recycling plants, or other industries that release lead; or children with siblings or playmates diagnosed with lead poisoning. Eliminating the lead source is the cornerstone of treatment. Chelation therapy generally is reserved for those children with blood-lead levels greater than 45 g/dL.