HLA-DR4 in ankylosing spondylitis with different patterns of joint involvement.

Fifty patients with ankylosing spondylitis (AS) confined to the spine and sacroiliac joints were compared with 50 cases of AS complicated by various patterns of non-axial joint involvement. Radiological and clinical features were evaluated and HLA-DR4 typing was carried out. This antigen was found in 16% of 200 normal individuals in 18% of patients suffering from exclusively axial AS, and in 54% of patients with additional purely peripheral joint involvement (wrist, finger, ankle, toe). The possibility that HLA-DR4 represents a non-specific marker for peripheral arthritis in patients with ankylosing spondylitis is discussed.