An 8-day-old neonate born to a 25-year-old woman is brought to the office due to progressive lethargy, vomiting, and poor feeding. The mother reports an uneventful pregnancy and perinatal course. She exclusively breastfeeds the infant and has no medical problems in any of her other children. On examination, the infant is somnolent and dehydrated with decreased muscle tone. Laboratory studies reveal metabolic acidosis with an elevated anion gap, ketosis, and hypoglycemia. Further evaluation reveals a markedly elevated propionic acid level due to defective conversion of propionyl-CoA to methylmalonyl-CoA. This patient is most likely unable to use which of the following amino acids for energy production?

Question

An 8-day-old neonate born to a 25-year-old woman is brought to the office due to progressive lethargy, vomiting, and poor feeding.  The mother reports an uneventful pregnancy and perinatal course.  She exclusively breastfeeds the infant and has no medical problems in any of her other children.  On examination, the infant is somnolent and dehydrated with decreased muscle tone.  Laboratory studies reveal metabolic acidosis with an elevated anion gap, ketosis, and hypoglycemia.  Further evaluation reveals a markedly elevated propionic acid level due to defective conversion of propionyl-CoA to methylmalonyl-CoA.  This patient is most likely unable to use which of the following amino acids for energy production?

Quizplus · Accepted Answer

Eductional Objective: Propionyl-CoA is derived from the metabolism of valine, isoleucine, methionine, threonine, and odd-chain fatty acids.  Congenital deficiency of propionyl-CoA carboxylase, the enzyme responsible for the conversion of propionyl-CoA to methylmalonyl-CoA, leads to the development of propionic acidemia.  The condition presents with lethargy, poor feeding, vomiting, and hypotonia 1-2 weeks after birth.

An 8-Day-Old Neonate Born to a 25-Year-Old Woman Is Brought