HLA markers in patients suffering from aplastic anaemia.

135 patients, suffering from aplastic anaemia (AA) and their families were genotyped for HLA. The antigen and haplotype frequencies were compared to an HLA genotyped control panel composed of 209 normal couples and their healthy offsprings, and to another series of 2286 normal individuals. An excess of HLA-A2 was observed in the patients: 61% versus 42% (pc less than 0.001) (relative risk: 2) and versus 48.5% (p less than 0.01) in two control series, respectively. When considering the HLA-A, B antigens shared in common by the parents of the AA patients, an excess of HLA-A2 was observed: 32% as compared to 17% shared by normal couples (p less than 0.001). An excess of homozygous HLA-A2 was noted in the AA patients (14%) in comparison to the normal controls (4%) (p less than 0.001). The mechanism of this association is discussed as well as the hypothesis of a gene involved in haematopoiesis which might interact within the HLA-A region.