C9 and myelodysplastic syndrome: A significant proportion of patients (45%) harbored germline variants in genes associated with inborn errors of immunity (IEI), such as AIRE, CFH, CFHR5, CR2, C2, C9, MASP1, LIG1, TNFRSF13B, and BLNK. Germline variants affecting complement genes were more prevalent in MDS-h patients than in AA patients (54% vs. 17%, p < 0.05).