A 3-week-old neonate presents with vomiting, lethargy, hypotonia, and metabolic acidosis with elevated anion gap. Plasma ammonia is 400 µmol/L. Plasma carnitine is low, and urine shows elevated methylcitrate and 3-hydroxypropionate. The enzyme deficient requires which cofactor?
- A Biotin ✓
- B Vitamin B12 (cobalamin)
- C Thiamine
- D Vitamin B6
Correct answer: A. Biotin
Explanation
The presentation with methylcitrate and 3-hydroxypropionate in urine indicates propionic acidemia (propionyl-CoA carboxylase deficiency). Propionyl-CoA carboxylase requires biotin as a cofactor. Methylmalonic acidemia would show methylmalonic acid elevation. A12-responsive methylmalonic acidemia involves methylmalonyl-CoA mutase or cobalamin cofactor defects, not propionyl-CoA carboxylase.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.