Analysis of the response of AA patients with different genotypes to treatment showed that the response rate of HLA‐LL(+)AA patients to IST was significantly higher than that of HLA‐LL(−)AA patients and HLA‐A homozygous patients and that the survival rate without bone marrow failure of untreated HLA‐LL(+)AA patients was also significantly higher than that of HLA‐LL(−)AA patients and HLA‐A homozygous patients. Here, HLA-A is linked to Bone marrow hypocellularity.