DHFR and megaloblastic anemia: IMDs leading to megaloblastic anemia through impaired folate metabolism include methylenetetrahydrofolate dehydrogenase 1—MTFHD1 (catalyzing 5,10-MTHF formation via the synthesis of 10-formyl-THF and 5,10-methenyl-THF), dihydrofolate reductase—DHFR (catalyzing the reduction of dihydrofolate to tetrahydrofolate and, at a lower rate, of folic acid to DHF) and formiminotransferase-cyclodeaminase (FTC) deficiencies [7,8,9].