NBME Pediatrics Form 2 - Answers & Explanations

Updated: Feb 25

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 discoloration under eyes” = periorbital ecchymoses (“raccoon eyes”) from periorbital metastasis

• Arises from neural crest cells (occurs anywhere along sympathetic chain)

• Median age of presentation is ≤ 2

32) ECG and chromosomal analysis

• Failure of O2 saturation to normalize with O2 administration = cardiac pathology

• Examination findings are consistent with Down syndrome, which is associated with VSD, ASD and AV septal defects

33) Formula with hydrolyzed casein • Soy protein-induced allergic proctocolitis • Tx: Elimination of milk & soy from maternal diet in breastfed infants • Tx: Switch to hydrolyzed (predigested proteins) formula in formula-fed infants

34) Hypothyroidism • History of autoimmune disease - Hashimoto thyroiditis is associated with DM I (HLA DR3), tiredness, palpable thyroid (goiter)

35) Respiratory distress syndrome of the newborn

• Surfactant deficiency → alveolar collapse & diffuse atelectasis

• Presents with severe respiratory distress & cyanosis after premature birth

• CXR: diffuse, reticulogranular (ground-glass) appearance, air bronchograms, low lung volumes

36) Fiberoptic endoscopy • Upper GI endoscopy should be performed within 24hrs of ingestion if there is no evidence of perforation or severe respiratory distress (after assessment of ABCs and decontamination)

37) Perform the operation, because it is an emergency and no consent is required

38) Normal development • BAG’M mnemonic for normal pubertal development (in years old)

• Breast - 8

• Axillary hair - 9

• Genital hair - 10

• Menarche - 11

• Precocious puberty = girls <8, boys <9

39) Cholelithiasis • Spherocytes are destroyed in the spleen; hemolysis of RBCs → ↑ risk of developing pigmented gallstones → cholelithiasis

40) Renal ultrasonography

• Children <24 months old with first febrile UTI → bladder and renal U/S

• Children <1 month old (with first febrile UTI or <24 months with recurrent UTI) → VCUG

41) Isoniazid only

• PPD >10 mm in a child <4 years old = positive PPD; PPD > 5mm with exposure to someone with TB = positive PPD

• Positive PPD + negative CXR = latent TB → give prophylactic isoniazid for 9months

42) Retinoblastoma

• DDx for leukocoria is Retinoblastoma (Rb) and Congenital cataracts

• Rb is a mass on the retina which can cause the eye to deviate (estropia) and can cause retinal vessel hemorrhage (hyphema - vessel hemorrhage in the anterior chamber)

43) Slit-lamp examination • Juvenile idiopathic arthritis = sxs arthritis for ≥6 weeks in a patient <16 years old

• Uveitis is common → requires slit-lamp exam for diagnosis

44) Decreased excretion of bilirubin

• Direct hyperbilirubinemia = >20% of total bilirubin is direct bilirubin

• Conjugated (direct) hyperbilirubinemia, hepatomegaly, acholic (pale) stools (due to absence of biliary pigment), dark urine (due to renal excretion of bilirubin) → Biliary atresia

• Gold standard diagnosis: intraoperative cholangiogram

• Tx: Hepatoportoenterostomy (Kasai procedure), Liver transplant

45) Recovery without renal sequelae • Post-streptococcal glomerulonephritis (PSGN) usually self-resolves without complications in children; adults may develop RPGN

46) SpirometryAsthma diagnosis requires PFT showing ↓ FEV1 that responds to albuterol

• Children <5 generally cant cooperate with PFT (indicated only in children >5 years old)

47) Decrease the insulin dosage by 10% to 15% only on practice days • Exercise → ↑ GLUT4 → ↑ uptake of glucose into cells (less insulin required)

48) Subglottic edema

• Croup → sub-glottic edema

Inspiratory stridor generally denotes upper respiratory pathology

• Breathing cool air (“improves when outside” [presume its cold out]) → vasoconstriction of subglottic vessels → reduced edema → improved sxs

• Tx: racemic epinephrine

49) Henoch-Schönlein purpura

• Palpable petechia/purpura on lower extremities with normal platelet count

• May also see arthralgia, colicky abdominal pain, and renal disease similar to IgA nephropathy

• Tx: Hydration + NSAIDs (supportive)

50) Reactive arthritis • Classic triad: conjunctivitis, urethritis, arthritis

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