Among genetic predispositions, the association of human leukocyte antigen (HLA), class I and class II alleles, and single nucleotide polymorphisms (SNPs) of the cytotoxic T-lymphocyte associated protein 4 (CTLA-4) gene (318 C/T, +49 A/G, and CT60 A/G) with AHA have been investigated. Here, CTLA4 is linked to autoimmune hemolytic anemia.