Unidirectional HLA Mismatch

**Semantic type:** Classification

**Definition:** The state when a recipient of a hematopoietic stem cell transplantation is not fully matched with their unrelated adult volunteer donor for HLA-A, HLA-B, HLA-C, and HLA-DRB1 and either the recipient or donor is heterozygous at one locus. Occurs when only the donor or recipient is homozygous.

**Synonyms:** - Unidirectional HLA Allele Mismatch - Unidirectional HLA Locus Mismatch