HLA frequencies and haplotypes in children with idiopathic thrombocytopenic purpura (ITP).

26 patients with an acute reversible ITP and 6 with chronic ITP were tissue typed, together with their healthy first-degree relatives. The HLA frequencies of the different groups were compared with those of a normal control population. The only significant difference between the groups was an increase in the frequency of Aw32 in acute ITP patients. HLA-Aw32 was present in 26.9% of patients, but in only 0.8% of the controls (corrected P = 0.000027). The possible importance of associations between antigens of the HLA-A locus with certain diseases are discussed. Family analyses and haplotype determinations proved to be unproductive because no familial clustering of ITP was found.