USMLE USMLE Certifications USMLE-STEP-2 Questions & Answers

• Question 431:

  A 13-year-old boy presents for evaluation of short stature. His growth chart from ages 2 through 12 years is shown in Figure. His growth in the first 2 years of life was typically at the 25th percentile. He has been healthy, has a good appetite, and is doing well in school. He lives with his parents and is an only child. His parents' heights are both at the 50th percentile. His father states that he grew several inches after he completed high school. A complete physical examination is normal. His Tanner stage is I Which of the following tests is the most appropriate next step in the care of this patient?

  A. bone age

  B. cranial imaging

  C. growth hormone stimulation

  D. thyroid function tests

  E. no tests are necessary

  Correct Answer: E

  Given that this is a classic case of constitutional growth delay, no diagnostic studies are indicated. Close monitoring of growth would be indicated. A bone age, if performed, would be less than chronologic age, demonstrating the growth potential for the patient. Cranial imaging would be indicated if the patient had evidence for onset of secondary hypopituitarism

• Question 432:

  A 13-year-old boy presents for evaluation of short stature. His growth chart from ages 2 through 12 years is shown in Figure. His growth in the first 2 years of life was typically at the 25th percentile. He has been healthy, has a good appetite, and is doing well in school. He lives with his parents and is an only child. His parents' heights are both at the 50th percentile. His father states that he grew several inches after he completed high school. A complete physical examination is normal. His Tanner stage is

  A. Which of the following is the most likely cause of this patient's short stature?

  B. constitutional delay

  C. deprivational dwarfism

  D. familial short stature

  E. growth hormone deficiency

  F. hypothyroidism

  Correct Answer: A

  Constitutional delay is a normal pattern of growth, characterized by a relatively late pubertal growth spurt. It is recognized most commonly in boys. Patients typically show a moderate degree of short stature in early to middle childhood. The growth pattern is often similar to one or both parents. Final adult height is within the expected genetic potential. The children are otherwise well. Familial short stature is also a normal growth pattern in a short but otherwise normal family. One or both parents are typically 12 standard deviations below mean height for adults. The growth pattern parallels the normal growth curve at a percentile consistent with genetic potential. Deprivational dwarfism is due to psychosocial factors. It typically presents at a younger age, and weight is affected more than the height so that these children are not proportionately small. Hypothyroidism can affect growth but would cause a decrease in growth velocity when it occurred. The patient's height curve would flatten out, instead of paralleling the normal curves. Short stature from growth hormone deficiency typically presents by 3 years.

• Question 433:

  An 18-month-old boy has received 5 days of amoxicillin for otitis media. He continues to have fever, and

  on physical examination, the right tympanic membrane is bulging with purulent fluid behind it.

  Which of the following is the best antibiotic to use?

  A. amoxicillin-clavulanic acid

  B. dicloxacillin

  C. cephalexin

  D. erythromycin

  E. penicillin

  Correct Answer: A

  Patients with persistent otitis media after 5 days of amoxicillin likely have resistant S. pneumoniae, or a beta-lactamase-positive M. catarrhalis or H. influenzae. Cephalexin, erythromycin, dicloxacillin, and penicillin would not cover the beta-lactamase-positive organisms. Some would recommend that the patient would benefit from a higher dose of the amoxicillin component in the combination antibiotic to provide better coverage for resistant S.

• Question 434:

  During a routine yearly checkup, a 10-year-old boy is found to have 2 + proteinuria on urinalysis. Which of the following would be the most appropriate diagnostic test?

  A. electrolytes, BUN, and serum creatinine

  B. antistreptococcal antibodies

  C. IVP

  D. renal ultrasound

  E. a repeat urinalysis

  Correct Answer: E

  Many healthy children have intermittent proteinuria. Transient proteinuria may occur with fever, strenuous exercise, and cold exposure. Testing for hematuria and RBCs and casts should be done. BP should also be checked. When proteinuria is intermittent and not accompanied by hematuria, chronic renal disease is unusual. Achild who has proteinuria on a single specimen, thus, will need repeated urinalyses. If isolated proteinuria is present in three consecutive urinalyses testing for orthostatic proteinuria should be considered. If this test is negative, qualitative measurement of proteinuria can confirm the diagnosis (>4 mg/m2/h) and further evaluation may be considered. If proteinuria remains intermittent, most physicians do not perform invasive procedures such as a biopsy. Proteinuria alone is unlikely to be an indicator of UTI or structural kidney disease; thus, an IVP and renal ultrasound are unlikely to be helpful. Likewise, with isolated and intermittent proteinuria as the only abnormality, electrolytes, BUN, and creatinine levels are highly unlikely to be abnormal.

• Question 435:

  A4-month-old child presents with a 2-day history of vomiting and intermittent irritability. On examination, "currant jelly" stool is noted in the diaper, and a sausage-shaped mass is palpated in the right upper quadrant of the abdomen. Which of the following conditions is most likely to cause this?

  A. appendicitis

  B. diaphragmatic hernia

  C. giardiasis

  D. intussusception

  E. rotavirus gastroenteritis

  Correct Answer: D

  Intussusception, or telescoping of the bowel into a more distal section of bowel, is the most common cause of intestinal obstruction in infants aged 312 months. The case presented represents the classic presentation. Giardiasis presents less acutely and would not be associated with a mass. In gastroenteritis, frequent loose stools without blood would be the major symptom. Diaphragmatic hernia occurs in newborns, and the major symptom is respiratory distress. Although appendicitis can occur in infants, it is very unusual.

• Question 436:

  Afew weeks after a presumed viral respiratory infection, a 4-year-old girl presents with bruising and petechiae. Bone marrow examination reveals increased numbers of megakaryocytes but is otherwise normal. Hb is 13.5 g/100 mL. Platelet count is 30,000/mm3. Which of the following would be appropriate for this child at this time?

  A. daily prednisone

  B. a transfusion of packed RBCs and platelets

  C. IV gamma globulin

  D. splenectomy

  E. no specific therapy

  Correct Answer: E

  Most cases of idiopathic thrombocytopenic purpura (ITP) in children are preceded by viral infections and, in contrast to adults, the great majority of children recover spontaneously. Although not all patients require therapy, most authorities suggest treating when the platelet count is less than 20,000. Standard treatment has been oral prednisone. Recently, IV gamma globulin has been shown to be effective. However, this agent is expensive and less convenient than oral prednisone. The child described in the question might reasonably be treated with either agent. Because the child's Hb is 13.3 g/100 mL, there is no indication for transfusion of RBCs. Although the platelet count is very low, platelet transfusions are short lived and generally are indicated only in the presence of serious bleeding, as, for example, from the GI tract. Thus, platelet transfusions are not indicated in this patient. Splenectomy is reserved for the very rare child who does not respond to conservative therapy or who develops chronic ITP.

• Question 437:

  A 2-year-old girl presents with fever of 39.3°C and irritability. She has had an upper respiratory tract infection for 4 days. On examination, the right ear is bulging and has poor movement on insufflation. Which of the following organisms is most likely responsible for these findings?

  A. S. pneumoniae

  B. S. aureus

  C. M. pneumoniae

  D. E. coli

  E. group A Streptococcus

  Correct Answer: A

  Nontypeable H. influenzae, S. pneumoniae, and M. catarrhalis are the most common bacterial pathogens in otitis media of children. S. aureus, E. coli, and group A Streptococci each account for 2% or less of all cases of otitis media in children beyond the neonatal period. Mycoplasma is thought to be an uncommon cause of otitis media

• Question 438:

  A 1-day-old infant who received silver nitrate eye drops in the delivery room is suffering from bilateral purulent conjunctival discharge. Which of the following is the most likely cause of this child's condition?

  A. N. gonorrhoeae infection

  B. herpes simplex infection

  C. nasolacrimal duct obstruction

  D. chemical irritation

  E. Pseudomonas infection

  Correct Answer: D

  Silver nitrate, the traditional prophylactic treatment for the neonate's eyes, is very effective against gonorrheal ophthalmitis. These drops are not effective against the most common cause of neonatal conjunctivitis, C. trachomatis, which requires erythromycin or tetracycline for eradication. Silver nitrate is commonly associated with the sterile purulent discharge of chemical conjunctivitis. HSV can cause neonatal conjunctivitis, but its occurrence on the first day of life would be unusual. Pseudomonas conjunctivitis generally is hospital acquired, occurring in ill infants receiving mechanical ventilation. Nasolacrimal duct obstruction is a transient structural anomaly that may be accompanied by persistent tearing and occasional purulent discharge. The condition is usually unilateral and clears within 69 months after birth. Rarely, duct probing or surgery is necessary because of persistent stenosis beyond 1 year of age or for repeated infections.

• Question 439:

  Children with sickle cell disease are at risk for certain conditions with characteristic presentation. Match the clinical scenario with the syndrome.

  A 5-year-old boy with sickle cell anemia presents with a 2-day history of increasing pain in both legs. He has had multiple admissions for similar episodes of pain. On examination, he has no swelling of the legs. There is diffuse tenderness along both legs. There is no joint involvement, and there is full range of movement.

  A. acute chest syndrome

  B. acute splenic sequestration

  C. aplastic crisis

  D. hand-foot syndrome

  E. Salmonella osteomyelitis

  F. vasoocclusive crisis

  Correct Answer: F

  Acute painful episodes are the most common manifestation of sickle cell disease. Most patients experience some pain nearly daily. In younger children, this usually involves the extremities. In older children, head, chest, abdomen, and back pain may occur.

• Question 440:

  Children with sickle cell disease are at risk for certain conditions with characteristic presentation.

  Match the clinical scenario with the syndrome.

  A 12-month old patient presents with a 3-day history of lethargy and fever. He has also had rhinorrhea and

  a cough. On physical examination, he is pale, tachycardic, and has a left upper quadrant mass. His

  hemoglobin is 4 g/dL, platelet count is 100,000, and WBC is 15,000 with 50% segmented neutrophils.

  His reticulocyte count is 15%.

  A. acute chest syndrome

  B. acute splenic sequestration

  C. aplastic crisis

  D. hand-foot syndrome

  E. Salmonella osteomyelitis

  F. vasoocclusive crisis

  Correct Answer: B

  This is the classic presentation of splenic sequestration which occurs in these patients in the first few years of life, before the spleen autoinfarcts. This often occurs following an acute febrile illness. Blood pools in the spleen, which becomes enlarged; signs of circulatory collapse may develop. In an aplastic crisis, a very low reticulocyte count would be expected, and there is no such splenic enlargement.