Combined Immunodeficiency and Megaloblastic Anemia with or Without Hyperhomocysteinemia, also known as methylenetetrahydrofolate dehydrogenase 1 deficiency, is related to autoimmune disease and hemolytic uremic syndrome, atypical 1. An important gene associated with Combined Immunodeficiency and Megaloblastic Anemia with or Without Hyperhomocysteinemia is MTHFD1 (Methylenetetrahydrofolate Dehydrogenase, Cyclohydrolase And Formyltetrahydrofolate Synthetase 1). Affiliated tissues include nk cells and b cells, and related phenotypes are seizure and intellectual disability, mild