Methionine synthase reductase (MTRR) is the locus of the cblE class of inborn errors of cobalamin metabolism that is characterized by megaloblastic anemia and homocystinuria.
Methionine synthase reductase (MSR) deficiency is an autosomal recessive disorder of folate/cobalamin metabolism leading to hyperhomocysteinemia, hypo- methioninemia and megaloblastic anemia.