Mondo Description An autosomal recessive condition caused by mutation(s) in the MTRR gene, encoding methionine synthase reductase. It is characterized by homocystinuria and megaloblastic anemia.

Uniprot Description An autosomal recessive inborn error of metabolism resulting from defects in the cobalamin-dependent pathway that converts homocysteine to methionine. It causes delayed psychomotor development, megaloblastic anemia, homocystinuria, and hypomethioninemia. Cells from patients with HMAE fail to incorporate methyltetrahydrofolate into methionine in whole cells, but cell extracts show normal methionine synthase activity in the presence of a reducing agent.