Haematopoietic regeneration by HLA‐A*0206‐deficient clones in severe aplastic anaemia without definitive immunosuppressive treatment

Summary We describe the case of a 74‐year‐old man with severe aplastic anaemia who experienced persistent remission attributed to proliferation of HLA allele‐deficient clones. Despite an initial worsening of pancytopenia with eltrombopag and ciclosporin treatment, gradual trilineage haematopoietic recovery occurred, with blood counts normalizing over 3 years. Flow cytometry and deep nucleotide sequencing revealed that haematopoiesis was primarily supported by several clones with somatic mutations that inactivated antigen presentation via HLA‐A*0206. This suggests that monitoring haematopoietic regeneration by immune escape clones could be an alternative approach for immune aplastic anaemia patients who possess HLA allele‐deficient clones and cannot tolerate standard therapy.