The HL‐A System in Reiter's Syndrome

The HL‐A phenotypes were determined in 50 patients with Reiter's syndrome. HL‐A27 was found in 34 (68%) compared to 7.7% of controls. There was an association between the presence of HL‐A27 and sacro‐iliitis, uveitis and keratoderma blenorrhagica. Reiter's syndrome was found to have occurred in HL‐A27 positive identical twins. In four sibships a brother, sharing a haplotype with the proband, was found to have spondylitis. There was evidence that in some HL‐A27 positive individuals spondylitis had developed prior to the first attack of Reiter's syndrome, suggesting that spondylitis and Reiter's syndrome may be separate disease processes in the one genetically predisposed individual. When Reiter's syndrome was associated with severe keratoderma blenorrhagica and widespread psoriasiform lesions, sometimes with persisting psoriasis or recurrent uveitis, HL‐A27 was present and HL‐A17 absent. There is some evidence that the HL‐A phenotype itself does not determine susceptibility to disease in HL‐A27 positive individuals but that linked immune response genes may be present.