A 3-year-old boy presents with fever and a petechial rash. Labs show leukocytosis and positive blood culture. Most likely diagnosis is:

Correct Answer: C

Rationale: Meningococcemia fits fever, petechiae, and positive culture, per CDC. A, B, D, E lack bacteremia.

Correct Answer: B

Rationale: Blackened stools A, darkened teeth B, and gastric irritation D are side effects I, II, IV, per document p5, 3.

Correct Answer: D

Rationale: All D are otitis media symptoms, per document p43, 9.

Correct Answer: C

Rationale: Cystic fibrosis fits pneumonia and positive sweat test, per CFF. A, B, D, E differ.

Correct Answer: A

Rationale: Congenital hepatic fibrosis (CHF) is strongly associated with autosomal recessive polycystic kidney disease (ARPKD) (Choice A), a ciliopathy causing renal cysts and hepatic fibrosis, often presenting together in childhood. Horseshoe kidney (Choice B) is a fusion anomaly unrelated to CHF. Multicystic dysplastic kidney (Choice C) is a unilateral developmental disorder, not linked to hepatic fibrosis. Nephronophthisis (Choice D) causes renal failure but lacks a consistent CHF association. ARPKD’s genetic and clinical overlap with CHF makes it the most common association.

Correct Answer: A

Rationale: Iatrogenic causes , like excessive saline, are the top source of hypernatremia in hospitalized kids (AAP). B-E are rarer.

Correct Answer: B

Rationale: Pyloric stenosis causes vomiting and alkalosis, per AAP. A, C-E differ.

Correct Answer: C

Rationale: Roseola features fever followed by a rash, per AAP. A, B, D, E have concurrent fever and rash.

Correct Answer: B

Rationale: Fever B is the leading cause febrile seizures, per document p29, 0.