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NBME Pediatrics Form 1 - Answers & Explanations

Updated: Mar 6, 2020


1) Impaired humoral immunity

Common variable immunodeficiency (CVID) → defect in B-cell differentiation → ↓ plasma cells and immunoglobulins → ↑ sinopulmonary infections

• Combine immunodeficiency (eg, SCID) would have evidence of recurrent/severe viral and fungal infections (not just bacterial infections)


2) Posterior urethral valves

• Most common cause of urinary tract obstruction in newborn boys

• Vesicoureteral reflux is a common cause of recurrent UTI in kids


3) Nasal polyps

• Chronic URIs and steatorrhea are consistent with cystic fibrosis (CF)

• ~10-40% of CF patients have nasal polyps (due to chronic inflammation)


4) Hypothermia

• J wave = positive deflection occurring at the junction between the QRS complex and the ST segment (J wave = Osborn wave)

• J wave are suggestive of hypothermia (but are not pathognomonic)

• Height of J wave is proportional to the degree of hypothermia


5) Pyloric stenosis

• Forceful, projectile, non-bilious vomiting

• Dehydration & weight loss

• Dx: abdominal U/S

• Tx: Pyloromyotomy


6) Exocrine pancreatic insufficiency

• Failure to thrive, steatorrhea, meconium ileus, ↓ soft-tissue mass (< 5th percentile for weight) = Cystic fibrosis (CF)

• Pancreatic insufficiency → malabsorption with steatorrhea → fat-soluble vitamin deficiencies (A, D, E, K)


7) Calcium

• Seizures & prolonged QT = symptoms of hypocalcemia

• Infants of diabetic mothers often have decreased magnesium and calcium

• Infants have difficulty absorbing calcium due to surpassed PTH (ketonuria → ↓ magnesium → suppression of PTH → ↓ calcium)


8) Thick and thin blood smears • This patient went to a chloroquine resistant area → malaria

9) Hyperglycemia

• Pseudo-hyponatremia from hyperglycemia

• Hyperglycemia causes osmotic shifts of water from the ICF to the ECF → dilution hyponatremia

• Hyperglycemia → ↑ diuresis → osmotic diuresis → hyponatremia


10) Herpes simplex virus • Temporal lobe hyper/hypo-densities = HSV • Herpes encephalopathy = ↑ RBC, normal glucose, ↑/normal protein, ↑ lymphocytes


11) Osteoporosis

• Modifiable risk factors for osteoporosis: ↓ physical activity, low body weight, excessive EtoH or tobacco use, premature menopause, glucocorticoid use

• This patient is headed toward the female athlete triad: low BMI, irregular periods, and

fractures


12) Tuberous sclerosis • Skin hypopigmentation = ash-leaf spots • Periventricular masses = subependymal astrocytomas


13) Major depressive disorder • This patient has ≥ 5 of the 9 diagnostic symptoms of SIG-E-CAPS for ≥ 2 weeks


14) Shigellosis

• Fever, campy abdominal pain, dysentery = Shigella

• Seizures = common neurologic complication of shigella; associated with fever > 39 °C (102.2 °F)

• Ekiri syndrome = lethal toxic encephalopathy due to shigellosis

• Characterized by rapid development of seizures and coma in patients with high fever and dysentery


15) Shallow, poorly developed acetabulum • Barlow & Ortolani maneuver to screen for developmental dysplasia of the hip

• “click” = femoral head dislocating posteriorly with reduction of the femoral head into the acetabulum

• More common in firstborn girls born in breech position


16) Trimethoprim-Sulfamethoxazole

• TMP-SMX inhibits enzymes in the DNA synthesis pathway → megaloblastic anemia, leukopenia, granulocytopenia

• Avoided with co-administration of leucovorin (folic acid)


17) Lymphocytic infiltration • Hashimoto thyroiditis → lymphocytic infiltrate (autoimmune process)

• Lymphoid aggregates with germinal centers

• MCC of hypothyroidism in iodine-sufficient regions


18) Impetigo contagiosa • Honey-crusted lesions ≈ Impetigo • Unlikely to be herpes simplex since the lips are spared


19) Legg-Calvé-Perthes disease • Commonly presents between 5-7 years old with insidious onset of hip pain

• Slipped capital femoral epiphysis commonly presents in obese pre-teens


20) Aplastic anemia • Aplastic anemia = pancytopenia (↓ RBC, ↓ WBC, ↓ Platelets)

• Aplastic crisis = ↓ Erythrocytes



21) T lymphocytes • T-cell deficit → fungal/viral infections


22) Venous hum

• Innocent, benign murmur in children

• Turbulent flow of venous return in the jugular veins and SVC; occurs during systole

and diastole

• Accentuated or eliminated with head position; disappears when supine or with digital compression of the jugular vein


23) Serum lipid studies

• AAP recommends universal lipid studies for kids age 9-11 (pre-puberty), and again at age 17-21 (post-puberty)

• “heart disease” in father and grandfather ≈ hypercholesterolemia


24) Cruciate incision of the hymen

• Adolescent girl at usually age of menarche presenting with amenorrhea, cyclic

abdominal/pelvic pain and hematocolpos = Imperforate Hymen

• Hematocolpos (blood-filled vagina) → bulging, blue hymen membrane


25) Silver stain of bronchoalveolar fluid • Pneumocystis pneumonia (caused by the yeast-like fungus Pneumocystis jirovecii)

• Mother had history of IV drug use • Baby’s frequent thrush and failure to thrive (FTT) = immunocompromised


26) Mixed metabolic acidosis and respiratory alkalosis

• Salicylate toxicity (early) stimulates medulla respiratory centers → hyperventilation → respiratory alkalosis

• Salicylate toxicity (late) decreases cellular respiration via uncoupling oxidative phosphorylation → anaerobic metabolism → metabolic acidosis

• This child was brought to the ED 20 minutes after her mother found her, not 20 minutes after ingestion of the aspirin...


27) Pathologic fracture of the humerus • Clear pathological fracture of the humerus on x-ray

• Ewing sarcoma → ‘onion skinning’


28) Sinusitis • >10 day history of fever, headache, and nasal discharge

• Post-nasal drip → erythematous posterior pharyngeal wall


29) Bacterial pneumonia • Decreased breath sounds, right lower lobe density (consolidation), abdominal pain (referred pain 2/2 diaphragmatic irritation from basal pneumonia or from overuse of abdominal muscles 2/2 persistent cough)


30) Myotonic dystrophy • Usually presents with facial weakness, hand grip myotonia, dysphagia

• Arises from autosomal dominant expansion of CTG trinucleotide


31) Inguinal hernia • “milked” = reducible hernia


32) Hepatitis A Virus: immune, Hepatitis B Virus: not immune

• Hepatitis A antibody = immune

• Anti-HBc (HBV core antibody); IgM indicates acute/recent infection, IgG indicates

prior exposure or chronic infection

• HBsAg (HBV surface antigen) indicates hepatitis B infection

• Lack of Anti-HBs (HBV surface antibody) indicates no immunity


33) Measurement of serum β-hCG concentration

• Always rule out pregnancy first, even if she hasn’t begun menstruation yet (tanner

stage is highly indicative of impending menstruation)

• X-ray & CT = radiation exposure = dangerous for potential fetus


34) Serial blood cultures • Fever + new systolic murmur (mitral regurgitation) = Endocarditis


35) Elimination of lead from the child’s home • Lead impairs heme synthesis → microcytic anemia


36) Adams-Stokes attack • P waves, no QRS = AV block • High grade AV block (ie, complete or Mobitz type II) = Stokes-Adams attack

• Tx: Pacemaker

37) Bronchoscopy • Foreign body → air-trapping → hyperinflation → hyper-resonance & ↓ breath sounds

• Bronchoscopy for removal of foreign body


38) Pulmonary artery hypertension • Eisenmenger’s syndrome: chronic left-to-right shunting → pulmonary artery HTN → shunt reversal → cyanosis and polycythemia


39) Reduced-calorie diet • Lifestyle (diet and exercise) modification is first-line (exercise should be aerobic; weight training = anaerobic exercise)


40) Phototherapy • Unconjugated hyperbilirubinemia from birth trauma (cephalohematoma)

• This baby has been breast-feeding and has normal stool & urine output

• If the child had a positive Coombs test and signs of acute bilirubin encephalopathy (eg, high-pitched cry, lethargy, poor feeding, and hypotonia), they should be treated with exchange transfusion as this is a medical emergency

• Mild elevation (>10 mg/dL) tx: phototherapy • Severe elevation (>20-25 mg/dL) tx: exchange transfusions



41) Cooking meats completely • Humans and animals are reservoirs for Salmonella species (except Salmonella typhi)

• Humans are the only reservoir for S. tyhphi • Poultry (BBQ chicken), eggs, pets, and turtles are common sources

• Non-typhoidal Salmonella → gastroenteritis


42) Strict hand-washing techniques at the day-care center • Rotavirus is transmitted through the fecal/oral route via contact with contaminated hands, surfaces, and objects.


43) Cerebral edema • Decreasing plasma osmolarity too quickly → fluid shifts from ECF to ICF → ↑ ICP

• ↑ ICP → absence of venous pulsations


44) Physiologic pubertal development • Gynecomastia occurs in ~33% of pubescent boys; goes away with development


45) A 6-week course of oral AZT within 12 hours after delivery * guidelines on this are in flux - unlikely to be tested* • If mother is HIV ⊕ then baby gets 6 weeks of of AZT within 6 hours of birth

• Wether to add on other antiretrovirals after that is based on moms viral load and other risk factors


46) Intravenous cefotaxime • High leukocyte count (indicates infection) warrants antibiotics • She already takes penicillin prophylaxis (the bug she has is probably resistant)

• 3rd generation cephalosporins treats possible meningitis


47) Staphylococcus aureus • Fungal infection → dry skin that cracked and allowed bacteria from the skin to get in → cellulitis 2/2 staph infection → fever & pain


48) Delayed, normal, normal • Child should be sitting up by himself after 6 months (this patient is 9 months old and is still unable)


49) Closure of the ductus arteriosus

• Cyanotic newborn with no improvement on O2 therapy = cardiac cause

• This patient likely has Coarctation of the aorta that is dependent upon the patent

ductus arteriosus (PDA is distal to the coarctation)

• PDA closure → new onset CHF (severe hypotension, poor perfusion, tachypnea,

hepatomegaly, unexplained metabolic acidosis)


50) Voiding cystourethrography

Question is out of date - Should be 'Observation for recurrent symptoms'

• Does not meet indications for VCUG (voiding cystourethrography)

• Posterior urethral valves are the most common cause of UTI in a baby boy

• Voiding cystourethrography checks the posterior urethral valves

• However, cystourethrogram is generally not indicated in first time UTIs unless U/S

shows hydronephrosis, scarring or the patient is < 1 month old




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10 Comments


Unknown member
Jun 02

Where can we find forms 1-4?

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karen beaty
karen beaty
May 12, 2023

This is from Nelson's 2023. Just to clarify why you would do phototherapy vs. exchange transfusion. The main reason is because the jaundice is from the cephalohematoma so you would only do exchange therapy once the level reached >25 mg/dl.


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#34) Serial blood cultures Fever + new systolic murmur (mitral regurgitation) = Endocarditis . This explanation makes no sense. The murmur is head at the left sternal border. There are also NO OTHER SIGNS of endocarditis. It would make MUCH MORE SENSE to have a splenic abcess due to ventral sept defect that lead to shunting of bacteria from venous circulation (maybe skin infection) to arterial and therefore the spleen. ALSO... this makes much more sense because it is one of the MCC of brain abcess in children (same mechanism)

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#40) you need to review the guidelines regarding the cut-off values for phototherapy Vs. exchange transfusions. They change according to time since birth, and that is why in this question it was the right answer.

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#15, “click” is not the same as CLUNK. One is normal, one is not.


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