Relapse with HLA loss after hematopoietic stem cell transplantation with non-HLA identical donor: Guidelines from the Francophone society of bone marrow transplantation and cellular therapy (SFGM-TC)

Loss of heterozygosity or HLA loss is a genomic-type escape mechanism highlighted in certain types of relapses after allogeneic hematopoietic stem cell transplantation with a non-HLA identical donor, and especially after haplo-identical transplantation. The diagnosis must be made with certainty because the result conditions the therapy. In this article, the different mechanisms and techniques that can be used for the diagnosis of loss of heterozygosity, as well as the therapeutic options are reviewed, making it possible to establish clinico-biological recommendations for the diagnosis confirmation and management of the patients in relapse.