Combined immunodeficiency and megaloblastic anemia with or without hyperhomocysteinemia (CIMAH) is a severe combined immunodeficiency resulting from MTHFD1 mutations. Variable phenotypes, including megaloblastic anemia, atypical hemolytic uremic syndrome, hyperhomocysteinemia, microangiopathy, infections and autoimmune diseases have been reported. MTHFD1 is a trifunctional enzyme that functions in the cytoplasmic folate cycle.
