methylmalonicacidemia /meth′əl·mə·lon′ik·as′i·dē′mē·ə/ , 1. an autosomal-recessive aminoacidopathy characterized by an excess of the carboxylic acid methylmalonic acid in the blood and urine, with metabolic ketoacidosis, hyperammonemia, and excess glycine in the blood and urine, presenting in infancy as failure to thrive, persistent vomiting and dehydration, respiratory distress, and hypotonia. It results from any of several defects that cause deficiency of an enzyme involved in the use of isoleucine, threonine, valine, propionate, and other odd-number chain-length fatty acids for fuel. Treatment consists of dietary supplementation with cobalamin, and carnitine and protein restriction; a diet restricting isoleucine threonine, methionine, and valine may be useful. Also called methylmalonicaciduria. 2. an excess of methylmalonic acid in the blood.
