USMLE USMLE Certifications USMLE-STEP-3 Questions & Answers

• Question 411:

  A mother relates seeing worms in her 3-yearold's stool. She describes them as 1-cm long white threads that seemed to be moving. What is the most likely infectious etiology for this finding?

  A. Ascaris lumbricoides

  B. Diphyllobothrium latum

  C. Taenia solium

  D. Toxocara canis

  E. Enterobius vermicularis

  Correct Answer: E Section: (none)

  Explanation:

  Pinworms (E. vermicularis) are common nematodes (roundworms) found in children. It usually is a benign, incidental finding, but can present with perianal pruritus or small, white, threadlike worms on visual examination. Ascariasis is the most common roundworm infection in humans, but these worms are larger.

  T. canis (dog roundworm) is another nematode and is the cause of visceral larval migrans. D. latum (fish tape worm) and Taenia solium (pork tape worm) are cestodes, which are long, flat worms.

• Question 412:

  A mother brings her 21/2-year-old daughter to your office for evaluation of frequent urination. The mother relates that the daughter seems to be urinating more frequently, up to 810 times in a day, over the past week. The girl complains of pain when she urinates, but the urine does not have any different odor to it. The mother says that the girl otherwise seems fine and still loves to take her bubble bath at night. The girl does not have a fever, weight loss, diarrhea, or vomiting What is the most likely diagnosis?

  A. pyelonephritis

  B. chemical urethritis

  C. retained vaginal foreign body

  D. type 1 diabetes mellitus

  E. diabetes insipidus

  Correct Answer: B Section: (none)

  Explanation:

  Polyuria in a prepubertal female may indicate the presence of a UTI. AUTI must be excluded as the first step. Polyuria may also indicate vulvovaginitis. Vulvovaginitis in a prepubertal female is usually irritation and hygiene related. The presence of dysuria with the polyuria would make the utility of checking fingerstick glucose, as a screening test for diabetes, low yield. The nightly use of bubble baths makes chemical urethritis the most likely cause of this girl's polyuria and dysuria. Diabetes mellitus would present typically with polyuria, polydipsia, weight loss, and decrease in energy. There would also be no dysuria unless there were a concomitant UTI. Diabetes insipidus is a very rare disease in childhood and would be unlikely in an otherwise healthy girl. The presence of a retained foreign body (typically toilet paper) is usually seen in conjunction with a vaginal odor and discharge as well.

• Question 413:

  A mother brings her 21/2-year-old daughter to your office for evaluation of frequent urination. The mother relates that the daughter seems to be urinating more frequently, up to 810 times in a day, over the past week. The girl complains of pain when she urinates, but the urine does not have any different odor to it. The mother says that the girl otherwise seems fine and still loves to take her bubble bath at night. The girl does not have a fever, weight loss, diarrhea, or vomiting.

  What is the most appropriate next step in evaluating this girl?

  A. fingerstick blood sample for random serum glucose

  B. plain abdominal x-ray

  C. clean urine sample for urinalysis and urine culture

  D. vaginal examination for discharge and cultures

  E. synchronized serum and urine osmolality

  Correct Answer: C Section: (none)

  Explanation:

  Polyuria in a prepubertal female may indicate the presence of a UTI. AUTI must be excluded as the first step. Polyuria may also indicate vulvovaginitis. Vulvovaginitis in a prepubertal female is usually irritation and hygiene related. The presence of dysuria with the polyuria would make the utility of checking fingerstick glucose, as a screening test for diabetes, low yield. The nightly use of bubble baths makes chemical urethritis the most likely cause of this girl's polyuria and dysuria. Diabetes mellitus would present typically with polyuria, polydipsia, weight loss, and decrease in energy. There would also be no dysuria unless there were a concomitant UTI. Diabetes insipidus is a very rare disease in childhood and would be unlikely in an otherwise healthy girl. The presence of a retained foreign body (typically toilet paper) is usually seen in conjunction with a vaginal odor and discharge as well.

• Question 414:

  A mother brings her 15-year-old son in for a preparticipation sports physical examination. She feels that her son has not yet undergone pubertal changes and that makes her concerned.

  Which of the following physical examination findings is usually the first sign of the onset of puberty in males?

  A. increased testicular volume

  B. increased skeletal muscle mass

  C. deepening of the voice

  D. increased facial hair

  E. physiologic gynecomastia

  Correct Answer: A Section: (none)

  Explanation:

  Pubarche in females is usually earlier than in males. Delayed puberty alone may be a pathologic condition; its presence in conjunction with short stature makes a pathologic state more likely. Males do, indeed, have adrenarche. Panhypopituitarism is a cause of puberty delay, but not a common one. Undiagnosed hypothyroidism can be a cause of pubertal delay, and thyroid function testing should be a part of the routine evaluation of this problem. The onset of puberty in males is usually signaled by an increase in testicular volume. This is commonly seen in conjunction with lengthening of the phallus and thinning of the scrotal skin. As a result of puberty, the other findings (deepening of the voice, increased muscle mass, and increased facial hair) may be seen, but the first of the listed findings to appear is increased testicular volume. In females, puberty is usually signaled by the enlargement of breast buds.

• Question 415:

  A mother brings her 15-year-old son in for a preparticipation sports physical examination. She feels that her son has not yet undergone pubertal changes and that makes her concerned.

  Which of the following is a true statement regarding puberty delay?

  A. The onset of puberty in males is earlier than that in females.

  B. A puberty delay is not considered pathologic unless accompanied by short stature.

  C. Hypothyroidism can be a cause of pubertal delay.

  D. Males do not have a true adrenarche as females do.

  E. The most common cause for pubertal delay is pan-hypopituitarism.

  Correct Answer: C Section: (none)

  Explanation:

  Pubarche in females is usually earlier than in males. Delayed puberty alone may be a pathologic condition; its presence in conjunction with short stature makes a pathologic state more likely. Males do, indeed, have adrenarche. Panhypopituitarism is a cause of puberty delay, but not a common one. Undiagnosed hypothyroidism can be a cause of pubertal delay, and thyroid function testing should be a part of the routine evaluation of this problem. The onset of puberty in males is usually signaled by an increase in testicular volume. This is commonly seen in conjunction with lengthening of the phallus and thinning of the scrotal skin. As a result of puberty, the other findings (deepening of the voice, increased muscle mass, and increased facial hair) may be seen, but the first of the listed findings to appear is increased testicular volume. In females, puberty is usually signaled by the enlargement of breast buds.

• Question 416:

  Parents bring their 12-year-old son to your clinic for evaluation. The child states that he gets teased a lot in school because of his short stature. His weight and height are below the 10th percentile for his age. His parents are of average height. Following your physical examination, you determine that he has tanner stage 1 development and his bone age is that of a 9-year-old male. His examination is otherwise normal. What is the most likely diagnosis?

  Which of the following is a true statement regarding the assessment of a child with short stature?

  A. An advanced bone age indicates that the child's final height will be greater than his peers.

  B. A slower growth velocity means the child will have more time to "catch up."

  C. A spot GH level is a good test in screening for GH deficiency.

  D. Somatomedin-C (ILGF-1) will be low in a child with GH deficiency.

  E. The most common cause of short stature in children is chronic renal disease.

  Correct Answer: D Section: (none)

  Explanation:

  Short stature in an adolescent is a common reason for visiting the pediatrician or endocrinologist. Most short stature in adolescence is constitutional growth delay. These children will have normal growth velocity and delayed bone age. Growth is normal for the first 412 months, then decelerates to below the fifth percentile. These children will catch up to their peers in a slightly delayed fashion. Frequently, other family members have a history of short stature in childhood, delayed puberty, and eventual normal stature as adults. In contrast, children with familial short stature have a normal bone age and regular onset of puberty. These children will maintain their short stature as adults. Somatomedin-C (ILGF-1) is commonly used as a surrogate measure for the end-organ effect of the pulsatile GH release. In children with GH deficiency, the end-organ effect will be a low somatomedin-C level. An advanced bone age (advanced bone maturation) usually results in shorter final height. Chronic renal failure is a cause of growth delay, but not a common one

• Question 417:

  Parents bring their 12-year-old son to your clinic for evaluation. The child states that he gets teased a lot in school because of his short stature. His weight and height are below the 10th percentile for his age. His parents are of average height. Following your physical examination, you determine that he has tanner stage 1 development and his bone age is that of a 9-year-old male. His examination is otherwise normal. What is the most likely diagnosis?

  A. familial short stature

  B. constitutional growth delay

  C. deficiency in GH

  D. chronic renal failure

  E. vitamin D deficiency

  Correct Answer: B Section: (none)

  Explanation: Short stature in an adolescent is a common reason for visiting the pediatrician or endocrinologist. Most short stature in adolescence is constitutional growth delay. These children will have normal growth velocity and delayed bone age. Growth is normal for the first 412 months, then decelerates to below the fifth percentile. These children will catch up to their peers in a slightly delayed fashion. Frequently, other family members have a history of short stature in childhood, delayed puberty, and eventual normal stature as adults. In contrast, children with familial short stature have a normal bone age and regular onset of puberty. These children will maintain their short stature as adults. Somatomedin-C (ILGF-1) is commonly used as a surrogate measure for the end-organ effect of the pulsatile GH release. In children with GH deficiency, the end-organ effect will be a low somatomedin-C level. An advanced bone age (advanced bone maturation) usually results in shorter final height. Chronic renal failure is a cause of growth delay, but not a common one

• Question 418:

  In January, you see an 18-month-old boy in the middle of the night in the pediatric emergency department.

  The father relates that 1 hour ago his son started coughing. The father describes the cough as barking

  ("seal" like). The child has mild stridor at rest, but otherwise is not in respiratory distress. His RR is 45

  breaths per minute. He has a temperature of 103.4°F .

  What is the most common x-ray finding in this illness?

  A. swollen adenoids

  B. the "thumb" sign

  C. a lobar pulmonary infiltrate

  D. a deviated tracheal air column

  E. the "steeple" sign

  Correct Answer: E Section: (none)

  Explanation:

  This case is a common presentation for viral croup, with the symptoms of a seal-barking cough, stridor, tachypnea, and fever in the winter. Pneumonia must also be considered with tachypnea, cough, and fever, but it is less likely to cause stridor and may not have the seal-bark type of cough. Sinusitis may cause cough and fever, but would be more likely to have a purulent nasal discharge and less likely to have the typical croupy cough. Bronchiolitis due to RSV is a common cause of wintertime cough and fever. It is less likely to have stridor and more likely to have wheezing. Children with epiglottitis are typically found in the "tripod position" and may be drooling. It is, fortunately, becoming rare with the widespread use of the H. influenzae vaccine. Parainfluenza types 1 and 2 account for 6070% of all viral croup. HIB was a common cause of epiglottitis, but is now rare because of widespread vaccinations. Influenza B and RSV can cause croup, but not as commonly as parainfluenza types 1 and 2. S. pneumoniae would be the most common bacterial cause of pneumonia or sinusitis. (American Academy of Pediatrics, 2003, pp. 454455) The steeple sign is subglottic narrowing of the trachea seen on an AP view of the trachea or a CXR. The trachea is seen to narrow, almost to a point, like the steeple of a church. Swollen adenoids are difficult to identify in lateral neck x-rays. The presence of swollen adenoids is unrelated to the airway narrowing seen in croup. The thumb sign is a swollen epiglottis seen with epiglottitis. Alobar pulmonary infiltrate may be seen with a typical bacterial pneumonia

• Question 419:

  In January, you see an 18-month-old boy in the middle of the night in the pediatric emergency department. The father relates that 1 hour ago his son started coughing. The father describes the cough as barking ("seal" like). The child has mild stridor at rest, but otherwise is not in respiratory distress. His RR is 45 breaths per minute. He has a temperature of 103.4°F . What is the most common etiology of this illness in children?

  A. HIB

  B. RSV

  C. influenza, type B

  D. parainfluenza, types 1 and 2

  E. S. pneumoniae

  Correct Answer: D Section: (none)

  Explanation: This case is a common presentation for viral croup, with the symptoms of a seal-barking cough, stridor, tachypnea, and fever in the winter. Pneumonia must also be considered with tachypnea, cough, and fever, but it is less likely to cause stridor and may not have the seal-bark type of cough. Sinusitis may cause cough and fever, but would be more likely to have a purulent nasal discharge and less likely to have the typical croupy cough. Bronchiolitis due to RSV is a common cause of wintertime cough and fever. It is less likely to have stridor and more likely to have wheezing. Children with epiglottitis are typically found in the "tripod position" and may be drooling. It is, fortunately, becoming rare with the widespread use of the H. influenzae vaccine. Parainfluenza types 1 and 2 account for 6070% of all viral croup. HIB was a common cause of epiglottitis, but is now rare because of widespread vaccinations. Influenza B and RSV can cause croup, but not as commonly as parainfluenza types 1 and 2. S. pneumoniae would be the most common bacterial cause of pneumonia or sinusitis. (American Academy of Pediatrics, 2003, pp. 454455) The steeple sign is subglottic narrowing of the trachea seen on an AP view of the trachea or a CXR. The trachea is seen to narrow, almost to a point, like the steeple of a church. Swollen adenoids are difficult to identify in lateral neck x-rays. The presence of swollen adenoids is unrelated to the airway narrowing seen in croup. The thumb sign is a swollen epiglottis seen with epiglottitis. Alobar pulmonary infiltrate may be seen with a typical bacterial pneumonia

• Question 420:

  In January, you see an 18-month-old boy in the middle of the night in the pediatric emergency department. The father relates that 1 hour ago his son started coughing. The father describes the cough as barking ("seal" like). The child has mild stridor at rest, but otherwise is not in respiratory distress. His RR is 45 breaths per minute. He has a temperature of 103.4°F .

  What is the most likely diagnosis?

  A. epiglottitis

  B. croup

  C. pneumonia

  D. sinusitis

  E. bronchiolitis

  Correct Answer: B Section: (none)

  Explanation: This case is a common presentation for viral croup, with the symptoms of a seal-barking cough, stridor, tachypnea, and fever in the winter. Pneumonia must also be considered with tachypnea, cough, and fever, but it is less likely to cause stridor and may not have the seal-bark type of cough. Sinusitis may cause cough and fever, but would be more likely to have a purulent nasal discharge and less likely to have the typical croupy cough. Bronchiolitis due to RSV is a common cause of wintertime cough and fever. It is less likely to have stridor and more likely to have wheezing. Children with epiglottitis are typically found in the "tripod position" and may be drooling. It is, fortunately, becoming rare with the widespread use of the H. influenzae vaccine. Parainfluenza types 1 and 2 account for 6070% of all viral croup. HIB was a common cause of epiglottitis, but is now rare because of widespread vaccinations. Influenza B and RSV can cause croup, but not as commonly as parainfluenza types 1 and 2. S. pneumoniae would be the most common bacterial cause of pneumonia or sinusitis. (American Academy of Pediatrics, 2003, pp. 454455) The steeple sign is subglottic narrowing of the trachea seen on an AP view of the trachea or a CXR. The trachea is seen to narrow, almost to a point, like the steeple of a church. Swollen adenoids are difficult to identify in lateral neck x-rays. The presence of swollen adenoids is unrelated to the airway narrowing seen in croup. The thumb sign is a swollen epiglottis seen with epiglottitis. Alobar pulmonary infiltrate may be seen with a typical bacterial pneumonia.