Methylmalonic acidemia with the unusual complication of severe hyperglycemia.

We describe a case of neonatal methylmalonic acidemia with the unusual complication of severe, insulin-resistant hyperglycemia. Methylmalonic acidemia, an inherited metabolic disease affecting the catabolism of propionic acid, is manifested by persistent metabolic acidosis, urinary excretion of large amounts of methylmalonic acid, and occasionally by hypoglycemia. Severe and persistent metabolic acidosis and hyperglycemia, despite large doses of insulin, were observed in this infant, who excreted large amounts of methylmalonic acid. The diagnosis of methylmalonic acidemia was confirmed by gas chromatography-mass spectroscopy, but the patient died before the defect in glucose tolerance could be delineated. We hypothesize that, in addition to the methylmalonic acidemia, the patient may have had an insulin-receptor defect, which was manifested as an inappropriate response to endogenous and exogenous insulin.