Shortly after birth, an infant presents with severe lactic acidemia, hyperammonemia, citrullinemia, and hyperlysinemia with the presence of α-ketoglurate in the urine. Definitive diagnoses of the causes of severe lactic acidemia are difficult and although these symptoms overlap with those seen with some of the urea cycle defect diseases, this is not the case with this neonate. A defect in which of the following enzymes would be expected to present with these findings?

Question

Quizplus · Accepted Answer

Pyruvate carboxylase is the first enzyme in the gluconeogenic conversion of pyruvate carbons into glucose. A defect in pyruvate carboxylase would restrict the conversion of lactate into pyruvate and then subsequently to glucose. This would lead to severe lactic academia. The other symptoms are primarily the result of liver damage due to impaired gluconeogenesis.

Shortly After Birth, an Infant Presents with Severe Lactic Acidemia