Inherited diseases of cobalamin (cbl) intracellular metabolism are very rare disorders affecting the synthesis of adenosylcobalamin or methylcobalamin. Methylcobalamin deficiency is generally characterized by homocystinuria and hypomethioninemia in the absence of methylmalonic aciduria (figure e-1 on the Neurology ® Web site at [www.neurology.org][1]). We report one of the oldest known patients with cblG disease (deficiency of methionine synthase). [1]: http://www.neurology.orgTest
