You are examining a 5-day-old neonate with ambiguous genitalia; there are no palpable gonads in the inguinal or genital area; the blood pressure is normal according to the age. Of the following, the NEXT step in the management of this neonate is

Correct Answer: B

Rationale: Chromosomal study (karyotype) is the next step to determine genetic sex in ambiguous genitalia, guiding further evaluation. Imaging (A) and hormone tests (C, D, E) follow based on karyotype results.

Correct Answer: D

Rationale: Metabolic disorders in neonates typically present with lethargy, poor tone, poor feeding, and seizures due to metabolic derangements. Hyperthermia is less characteristic, as these infants often have hypothermia from energy failure, making it the exception.

Correct Answer: C

Rationale: Galactosemia’s renal tubular dysfunction causes a normal-anion-gap hyperchloremic metabolic acidosis due to impaired bicarbonate reabsorption, consistent with proximal tubulopathy.

Correct Answer: A

Rationale: Hyperammonemia treatment includes ammonia scavengers (B), dialysis (C, D, E), but IV glucose alone doesn’t remove ammonia, though it prevents catabolism; it’s not a primary treatment here.

Correct Answer: C

Rationale: MPS III (Sanfilippo) spares the cornea but causes retinal degeneration and can lead to papilledema from CNS involvement, unlike other MPS types with corneal clouding.