Two cases of acute lymphoid leukemia patients with loss of heterozygosity in HLA region before transplantation.

Leukemia is a complex disease in which mutations and other genomic and epigenomic abnormalities play a role in both its initiation and progression. Acute lymphoid leukemia (ALL) patients with loss of heterozygosity (LOH) in the HLA region before transplantation have been described rarely. In this report, we described two ALL cases with LOH encompassing the HLA, wholly or partly. HLA molecular typing was performed on peripheral blood (PB) and somatic cell. Simultaneously, we performed whole-exome sequencing. Typing results on PB samples collected during blast crisis demonstrated complete or partial homozygosity at the -A, -B, -C, -DR, and -DQ loci. Two somatic samples demonstrated heterozygosity at all loci. LOH at the HLA gene locus may significantly influence the donor search, resulting in misidentification of homozygous donors. We recommend confirming the patients' HLA typing with hematological malignancies when homozygosity is detected at any locus by using somatic samples or alternatively from PB when remission is achieved.