USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 481:

  A 4-year-old child was brought in for evaluation of sleep problems. He cried and screamed within an hour of falling asleep. He seemed disoriented and confused; he did not seem aware of his parents' presence. They were unable to arouse him to comfort him. This resolved spontaneously, and he had no recollection of the event the next morning. You informed the parents that he was most likely experiencing which of the following?

  A. nightmares

  B. night terrors

  C. somnambulism

  D. somniloquy

  E. narcolepsy

  Correct Answer: B

  Parasomnias or disorders of arousal include nightmares, night terrors, sleepwalking (somnambulism), and sleep talking (somniloquy). This pattern suggests night terrors and is most common between ages 2 and 6 years. Nightmares occur at any age but peak between ages 3 and 5 years; they occur later in the night during rapid eye movement (REM) sleep. The child usually remembers the dream vividly, is upset on waking, but can be comforted by the parent. Sleepwalking occurs, as do night terrors, during non-REM sleep. It is most common between ages 4 and 8 years; safety of the child is the main concern. Sleep talking is not specific to any stage of sleep and may occur in association with nightmares and night terrors. Narcolepsy is a rare disorder characterized by excessive daytime sleepiness. Confirmation requires referral to a sleep laboratory

• Question 482:

  A full-term newborn develops cyanosis a few hours after birth. Oxygen administration does not improve color or oxygen saturations. Which of the following is the most likely diagnosis?

  A. atrial septal defect

  B. ventricular septal defect

  C. patent ductus arteriosus

  D. aortic stenosis

  E. pulmonary stenosis

  Correct Answer: E

  Cyanosis in newborn infants is associated with major right-to-left shunts. Total anomalous pulmonary venous return results in a right-toleft shunting through an interatrial communication, usually a patent foramen ovale. Patent ductus arteriosus and atrial septal defect, when unaccompanied by other cardiovascular abnormalities, cause left-to-right shunts that do not produce cyanosis. Coarctation of the aorta does not typically cause symptoms in the newborn.

  Hypoplastic left heart presents with signs of failure in the newborn period.

• Question 483:

  A 10-year-old boy is brought in with a chief complaint of multiple colds. On further questioning, you elicit a history of chronic, clear nasal discharge with no seasonal variation. Other symptoms include sneezing, itching of the nose and eyes, as well as tearing and occasional eye redness. Some relief is obtained with an over-the-counter cold medicine containing antihistamine and a decongestant. His history suggests which of the following?

  A. nasal foreign body

  B. immunologic deficiency

  C. rhinitis medicamentosa

  D. chronic sinusitis

  E. allergic rhinitis

  Correct Answer: E

  The symptoms are suggestive of perennial allergic rhinitis. Causative agents are usually those to which the child is exposed year round, such as house dust, mold spores, or pet danders. Seasonal allergic rhinitis is attributable to sensitization to pollens of trees, grasses, and weeds. Nasal foreign bodies usually result in a foul smelling, unilateral purulent, and occasionally blood tinged, discharge. Recurrent infections may rarely be attributable to immunologic deficiencies. Recurrent pneumonias are the most common complaint. Rhinitis medicamentosa occurs secondary to excessive use of vasoconstrictor nose drops or sprays, resulting in rebound nasal obstruction. Sinusitis is suggested by a bilateral purulent nasal discharge, often accompanied by fever, cough, headache, and sometimes sinus tenderness.

• Question 484:

  A 6-year-old Caucasian female has breast enlargement (Tanner stage II) and coarse curly pubic hair. She

  is not yet menstruating. She is otherwise healthy and has normal growth parameters. There are no signs

  of virilization and her abdominal examination reveals no masses. Examination of the vaginal area shows

  signs of estrogenization.

  On laboratory evaluation, you find elevated levels of follicle-stimulating hormone (FSH), luteinizing

  hormone (LH), and pubertal levels of estradiol. The bone age is advanced beyond the height and

  chronologic age.

  The most likely cause is which of the following?

  A. idiopathic

  B. central nervous system (CNS) tumor

  C. ovarian tumor

  D. functional ovarian cyst

  E. congenital adrenal hyperplasia

  Correct Answer: A

  The laboratory and radiologic studies indicate a form of central precocious puberty. It is most likely to be idiopathic; however, imaging of the head as well as a careful neurologic and visual examination is recommended to exclude a CNS lesion (tumor, trauma, hamartoma, and so forth). Estradiol secreting ovarian tumors and functional ovarian cysts may cause peripheral precocious puberty; however, the levels of FSH and LH are prepubertal. Congenital adrenal hyperplasia results in signs of virilization; these include excessive hirsutism, deepening voice, acne, clitoromegaly, and muscle development.

• Question 485:

  A 6-year-old Caucasian female has breast enlargement (Tanner stage II) and coarse curly pubic hair. She is not yet menstruating. She is otherwise healthy and has normal growth parameters. There are no signs of virilization and her abdominal examination reveals no masses. Examination of the vaginal area shows signs of estrogenization. Which of the following is the most likely preliminary working diagnosis?

  A. precocious puberty

  B. premature thelarche

  C. premature pubarche

  D. normal development

  E. precocious menarche

  Correct Answer: A

  Precocious puberty has been redefined for girls as the presence of either pubic hair or breast development before age 6 for African Americans and age 7 for Caucasians. Premature thelarche is the isolated development of breasts, with no other secondary sexual development. Premature pubarche is the isolated development of pubic or axillary hair (sexual hair). Precocious menarche is a rare form of incomplete precocious puberty with cyclic menstruation but no other secondary sexual characteristics.

• Question 486:

  Aweek-old infant presents blood in his stools. He was born at home, with the father assisting in the delivery; no physician or midwife was present. He has been breast-fed and has been nursing well. On examination, you also note some blood in his nose. He is not jaundiced; a rectal examination and guaic test of the stool confirms that blood is present. His examination is otherwise normal. He is on no medications.

  Which of the following is the most likely diagnosis?

  A. child abuse

  B. vitamin K deficiency

  C. breast milk allergy

  D. sepsis

  E. liver disease

  Correct Answer: B

  Neonates are routinely given intramuscular vitamin K at the time of birth. This is done to prevent the transient deficiency of vitamin- K-dependent factors, which occurs because of absence of bacterial intestinal flora which synthesize vitamin K. Hemorrhagic disease in the newborn because of vitamin K deficiency may result in GI, nasal, subgaleal, and intracranial bleeding, or bleeding after circumcision. The prothrombin time (PT), partial thromboplastin time (PTT), and bleeding time are prolonged. These all correct after administration of vitamin K. Child abuse should always be considered with unusual bleeding, but the history reveals the etiology in this case. Babies are more likely to be allergic to formula than breast milk; however, it occurs rarely and may present with bloody stools. It does not, however, cause epistaxis. Neonatal sepsis may result in disseminated intravascular coagulation and bleeding; the infant is usually ill appearing, with associated acidosis or shock. Liver disease may cause factor deficiencies and should be excluded if there is no response to vitamin K.

• Question 487:

  A15-month-old African American male, who is otherwise healthy, is found to have an emoglobin level of 8 g/dL on routine screening. The mean corpuscular volume (MCV) is decreased. His lead screen is within normal limits. You obtain a diet history, which reveals that he drinks about 3040 oz of whole cow's milk a day. He eats no meat and some fruits and vegetables.

  The most effective next step in management would be to obtain which of the following?

  A. iron studies--serum iron, total iron binding capacity, ferritin

  B. reticulocyte count

  C. hemoglobin electrophoresis

  D. a repeat hemoglobin in 1 month after treatment with folic acid

  E. a repeat hemoglobin in 1 month after treatment with iron

  Correct Answer: E

  If iron deficiency is strongly suspected, it is reasonable to treat empirically with 36 mg/kg/day of elemental iron. An increase in hemoglobin of 1 g/dL within 24 weeks confirms the diagnosis. If laboratory confirmation is necessary because the child is at low risk for iron deficiency, confirmatory iron studies may be obtained. The serum iron is low, the total iron binding capacity high, and the ferritin is low. Areticulocyte count is helpful in hemolytic anemias where it is elevated. Bone marrow aspirate in iron deficiency is necessary if bone marrow infiltration is suspected (leukemia), but is overinvasive in this situation. Hemoglobin electrophoresis may be done if thalassemia or sickle cell anemia is likely.

• Question 488:

  A15-month-old African American male, who is otherwise healthy, is found to have an emoglobin level of 8 g/dL on routine screening. The mean corpuscular volume (MCV) is decreased. His lead screen is within normal limits. You obtain a diet history, which reveals that he drinks about 3040 oz of whole cow's milk a day. He eats no meat and some fruits and vegetables.

  Which of the following is the most likely cause?

  A. sickle cell anemia

  B. thalassemia major

  C. lead poisoning

  D. iron-deficiency anemia

  E. anemia of chronic disease

  Correct Answer: D

  Iron deficiency is the most common cause of microcytic anemia. In children it is often related to excessive consumption of cow's milk, which is low in iron content, and inadequate consumption of iron-rich foods. Allergy to cow's milk may also cause occult GI blood losses. In thalassemia major, there is usually physical evidence of chronic anemia with signs of bone marrow expansion (frontal bossing) and severe anemia often requiring transfusions. Lead poisoning may cause microcytic anemias; it may also be associated with iron-deficiency anemia, which enhances lead absorption and, therefore, should always be excluded. Anemia of chronic disease (renal disease) may be microcytic or normocytic and should be excluded by history and examination.

• Question 489:

  A 4-year-old previously healthy but unimmunized boy presents with sudden onset of high fever, inspiratory stridor, and refusal to drink. Of the following causes of inspiratory stridor, which best fits this clinical scenario?

  A. epiglottitis

  B. vascular ring

  C. croup

  D. foreign body aspiration

  E. laryngeal tumor

  Correct Answer: A

  Croup and epiglottitis have similar presentations but need to be distinguished immediately. Croup usually results from a viral infection of the larynx and epiglottitis from a bacterial (H. influenzae type B) infection of the epiglottis. Children with epiglottitis tend to be toxic in appearance. Croup involves the airway, and epiglottitis involves the airway and the digestive tract. Children with croup usually will swallow and drink. Children with epiglottitis most often will refuse to drink and may even drool as a result of their refusal to swallow saliva. Patients with foreign bodies in their upper airways do not typically have fever. Patients with vascular rings and laryngeal tumors have more gradual onset of symptoms.

• Question 490:

  A5-year-old pedestrian is hit by a car in a mall parking lot and he is brought to the emergency department. There was loss of consciousness for less than 1 minute. On evaluation, the child has no neurologic deficits and a CT scan of the head reveals no intracranial abnormalities and no obvious skull fractures. The parents want to know what possible long-term problems there might be. You remember that problems after head trauma may include the development of seizures and that the risk of developing posttraumatic epilepsy is increased by which of the following?

  A. a brief loss of consciousness

  B. an acute intracranial hemorrhage

  C. retrograde amnesia

  D. posttraumatic vomiting

  E. a small linear skull fracture

  Correct Answer: B

  Late posttraumatic epilepsy is diagnosed when a seizure occurs for the first time more than 1 week after a head injury. Factors that correlate with an increased risk of developing posttraumatic epilepsy include presence of a depressed skull fracture, acute intracranial hemorrhage, cerebral contusion, or unconsciousness lasting more than 24 hours. Because the risk of a subsequent seizure is approximately 75%, acute and chronic treatment with anticonvulsants is indicated. Loss of consciousness, retrograde amnesia, and vomiting are relatively common immediate consequences of head trauma. They are usually transient and are not highly correlated with a risk of subsequent posttraumatic seizures.