The HLA-system in immune thrombocytopenic purpura: its relation to the outcome of therapy.

The distribution of HLA-A, -B, -C and -DR antigens was investigated in 154 patients with immune thrombocytopenia (99 adults and 55 children). An increased frequency of HLA-Bw56 (a split of HLA-Bw22) was found both in the adults (RR = 4.30) as well as in the children (RR = 7.91). Differences in HLA antigen distributions have also been analysed in patient subgroups with a good and a bad response to corticosteroids and splenectomy. The frequency of HLA-DR4 was low in those patients with a good response to prednisone as compared with those with a poor response. The opposite was found in splenectomized patients. In 22 patients who did not respond to splenectomy, LB4 (a local split of HLA-DR4) was completely absent. These results suggest that HLA-DR4 (LB4) may be a predictive marker for therapy in ITP patients, i.e. a bad response to corticosteroids and a favourable outcome of splenectomy. However, none of the differences were significant after correction was made for the number of antigens tested.