Methylmalonicaciduria, vitamin B12 unresponsive, mut 0 is due to methylmalonyl-CoA-mutase deficiency, an enzyme that is common to the catabolism of valine, isoleucine, methionine, and threonine. Methylmalonyl-CoA-mutase transforms methylmalonate into succinate. Onset is usually infantile with ketoacidotic coma, dehydration, hyperammonemia, and leucothrombocytopenia. A subacute form begins during early childhood with vomiting, hypotonia, growth and psychomotor retardation. Finally there is a later form characterized by recurrent ketoacidotic comas. Complications include growth and psychomotor retardation, pancreatitis glomerulointerstitial nephropathy, and acute central grey nuclei disorders causing extrapyramidal signs. The disease is transmitted as an autosomal recessive trait. Diagnosis is based on urinary organic acids and plasmatic acyls carnitine chromatographies that show high level of methyl malonic acid and proprionyl carnitine. Aminoacids chromatography reveals hyperglycinemia with a large total and free hypocarnitinemia. Diagnosis is confirmed by measuring methylmalonate coA mutase enzyme. Antenatal diagnosis is feasible. Patients should follow a strict, lifelong diet with limited protein intake. Treatment otherwise includes carnitine and antibiotics to destroy intestinal bacteria that produce propionic acid.
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