Homocystinuria and megaloblastic anemia responsive to vitamin B-12 therapy

A case study of an infant with an inborn cobalamin (vitamin B-12) dependency and megaloblastic anemia and homocystinura without methylmalonic aciduria or vitamin B-12 or folate deficiency is discussed. Successful therapy was achieved using hydroxocobalamin (but not using cyanocobalamin and folic acid). Tissue culture of fibroblasts revealed an intracellular deject for methionine synthesis and an absolute growth requirement for methionine. Intracellular methylcobalamin also was depressed. The study results indicated an impairment in the formation or accumulation of methylcobalamin, but not of adenosylcobalamin. (wz)