Henoch-Schönlein purpura and Crohn's disease in a family.

A 16-year-old female who underwent an appendicectomy had terminal segmental ileitis, and developed Henoch-Schonlein purpura (HSP) a few days later. Her brother had suffered from post-infection HSP, while her mother has suffered from Crohn's disease. Human leukocyte antigen (HLA) typing in the patient disclosed the DRB1*11 allele, which has been reported to be associated with HSP, but the brother proved negative, suggesting that this allele was irrelevant to the HSP pathogenesis. The patient and the other relatives did not disclose HLA DRB1*01, which is the only class II phenotype reported to be associated with both diseases. While this case report lends support to the idea that the earlier observation of concomitant Crohn's disease and HSP in the same patients is no chance association, it suggests that if the two pathological conditions share a common genetic background, this does not seem to be related to class II HLA phenotypes. Other, as yet unknown genes could be involved.