Hereditary Defect of Cobalamin Metabolism (CblGMutation) Presenting as a Neurologic Disorder in Adulthood

AN increasing variety of hereditary disorders of intracellular cobalamin metabolism, usually first detected because of the presence of methylmalonic aciduria (cblA, cblB, and cblF mutations), homocystinuria (cblE and cblG mutations), or both (cbIC and cblD mutations), have been defined on the basis of complementation studies.1 , 2 Methylmalonic aciduria results when the conversion of methylmalonyl-CoA (coenzyme A) to succinyl-CoA by methylmalonyl-CoA mutase, mediated by 5′-deoxyadenosylcobalamin, becomes impaired. Homocystinuria occurs when methylcobalamin and its cofactor, 5-methyltetrahydrofolate, cannot be used in the methylation of homocysteine to methionine, mediated by methionine synthase.Neurologic dysfunction and often megaloblastic anemia are prominent signs . . .