NBME Pediatrics Form 2 - Answers & Explanations

Updated: Feb 25, 2020

1) Determination of bone age

• Constitutional growth delay is possible (father was short until senior year) and is characterized by delayed growth spurt, delayed puberty, and delayed bone age

• If bone age < chronological age, then this child has room to catchup

2) Diazepam

• Generalized convulsive Status epilepticus (GCSE) = continuous seizure lasting >5 minutes

• GCSE requires immediate pharmacologic therapy with a benzodiazepine

• Lorazepam is first-line; Diazepam may be substituted if lorazepam is not available

3) Treponemia pallidum

• Painless, single lesion with clean base - Syphilitic chancre

4) Bronchopulmonary dysplasia

• BPD = chronic lung disease that affects newborns (mostly premature) and infants

• Results from damage to the lungs caused by mechanical ventilation and long-term use of O2

• Right heart hypertrophy is likely due to pulmonary HTN

5) Penicillin

• Asplenia → ↑ risk of encapsulated infection → prophylactic penicillin

6) B-lymphocyte function

• Bruton agammaglobulinemia is x-linked (brother and three uncles) → recurrent bacterial and enteroviral infections after 6 months of age (maternal Ig wanes)

• Patients immunizations are up to date, thus he shouldn’t be infected with HIB (vaccine-derived immunity requires the production of immunoglobulins)

• Total lymphocytes may be at a normal level (with B-lymphocytes diminished)

7) Torsion of the testis

• Sudden onset of scrotal pain (hours), absent cremasteric reflex = testicular torsions

• Gradual onset of scrotal pain (days), normal cremasteric reflex = acute epididymitis

8) Acute otitis media • Bulging or fullness of tympanic membrane = Acute otitis media (AOM); helps differentiate AOM from otitis media with effusion (OME)

9) Intravenous immune globulin therapy • Kawasaki disease - IVIG reduces risk of coronary artery aneurysm

• Aspirin is used for antiplatelet effects

10) Acetaminophen therapy

• Normal WBC + low grade fever → supportive care

11) Plasma cortisol

• Addisons Hypoaldosteronism

• Cortisol feedback inhibits pituitary CRH/ACTH; low cortisol → ↑ ACTH → darkening complexion (↑ POMC)

12) Air-contrast enema

• Intussusception

• Clinical presentation: sausage-shaped abdominal mass, intermittent abdominal pain, lethargy/altered mental status, “currant jelly” stools

• Tx: Air or saline enema, surgery for removal of a lead point

13) Ventricular septal defect

• Holosystolic murmur at left sternal border with a diastolic rumble over the apex = VSD

• Diastolic rumble is heard due to increased flow across the mitral valve

14) Impaired renal perfusion • BUN/Cr > 20:1 = prerenal injury = decreased renal perfusion

15) Exchange transfusion

• Bilirubin keeps rising regardless of phototherapy for 24hrs - must perform exchange transfusion before further deterioration and development of kernicterus

• Phototherapy indications:

○ 24 hours of age: > 12

○ 48 hours of age: > 15

○ 72 hours of age: > 18

• Exchange transfusion indications:

○ 24 hours of age: > 19

○ 48 hours of age: > 22

○ 72 hours of age: > 24

○ >72 hours of age: ≥ 25

16) Karyotype analysis • Short stature, weak femoral pulses (coarctation of the aorta) is consistent with Turner syndrome (45, XO)

17) Tinea versicolor • Pruritic hypo-pigmented spots = tinea versicolor; non-pruritic hypo-pigmented spots = vitiligo

18) Replication of a live vaccine virus strain • A small fraction of patients develop a self-limiting mild rash and fever 1-3 weeks after vaccination

19) Hemolytic disease of the newborn • Hemolytic disease of the newborn can occur due to ABO incompatibility (mom is O, baby is A or B) or Rh factor (If mom is Rh⊖ and baby is Rh⊕)

20) Systemic lupus erythematosus • Lupus characteristically presents in childhood with neuropsychiatric sxs • Other features: pancytopenia, arthritis, renal disease (UA showing protein and blood)

21) Nephroblastoma (Wilms tumor)

• Most common renal malignancy of childhood (usually between 2-5 years old)

• Asymptomatic abdominal mass that doesn’t cross the midline (vs. neuroblastoma which is symptomatic and crosses the midline)

22) Cytomegalovirus • Periventricular plaques/calcifications = CMV • Diffuse plaques/calcifications = Toxoplasmosis

23) Neurofibromatosis, type 1 • Presents with Café-au-lait macules (coffee-stain), axillary & inguinal freckling, Neurofibromas

24) Infertility • “Bag of worms” = varicocele • ↑ temperature → ↓ spermatogenesis → infertility

25) Tibia vara

• Blount’s disease - growth disorder of the tibia with inward turning of the lower leg (bowing) that worsens over time

• Risk factors = obesity, early walking

• Bowleg ≤ 2 years old = Physiologic bowleg; >2 years old = pathologic

26) Hemolytic-uremic syndrome

• Triad of HUS: anemia, thrombocytopenia, AKI

• Shiga toxin E coli O157:H7 has preceding bloody diarrhea and induces endothelial damage in renal glomeruli → platelet activation & microthrombi formation → thrombocytopenia & microangiopathic hemolytic anemia (MAHA) → schistocytes → ↑ bilirubin → scleral icterus

27) Metabolic • Goat milk is deficient in vitamin D → Rickets

28) Observation

• Only a hemangioma that compromises vision or the airway require intervention

• Infantile hemangioma have rapid growth at 5-7 weeks, stabilize at 4-6 months, and involutes around 4-6 years

29) Abnormal caudal migration of ganglion cells

• Failure of neural crest migration → distal segment of colon lacks Auerbach & Meissner plexuses

• Normal portion of colon proximal to aganglionic segment is dilated (“abrupt change

in caliber...”)

• ⊕ squirt sign

30) Midgut volvulus

• Sudden onset of constipation, bilious vomiting (obstruction below level of duodenum)

• Evaluation of bilious emesis in a neonate begins with cessation of enteral feeds, NG

tube decompression, and IV fluids. An X-ray is generally the first step to rule out pneumoperitoneum (intestinal perforation)

• Intussusception would present with colicky intermittent abdominal pain and currant jelly stools

31) Neuroblastoma

• “blueish discolorat