In a recent study of patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS) who underwent HSCT from HLA-matched related donors, we found that SIRPα variant mismatch between donor and recipient pairs was relatively common, and SIRPα mismatch was associated with a significantly higher risk of chronic GVHD (cGVHD) and lower risk of relapse (5). The gene discussed is SIRPA; the disease is myelodysplastic syndrome.