Which type of deficiency is associated with high levels of ammonia and poor feeding in infants?

High levels of ammonia in the blood, known as hyperammonemia, along with poor feeding in infants, are characteristic features of urea cycle disorders. The urea cycle is a series of biochemical reactions in the liver that convert ammonia, a toxic byproduct of protein metabolism, into urea, which is then excreted from the body through urine. When there is a deficiency in one of the enzymes involved in this cycle, ammonia accumulates because it cannot be effectively converted to urea. This accumulation can lead to significant neurological symptoms and feed intolerance in infants.

While other types of metabolic disorders could present with feeding issues or other symptoms, they do not typically cause the specific combination of high ammonia levels and poor feeding that are hallmarks of urea cycle defects. For instance, fatty acid oxidation disorders primarily lead to issues related to energy metabolism, while carbohydrate metabolism disorders would involve disturbances in glucose handling. Amino acid metabolism disorders may cause different issues related to the metabolism of specific amino acids, but they would not be predominantly associated with elevated ammonia levels in the same manner as urea cycle disorders.