HL-A W27 in psoriatic arthropathy.

Forty subjects with psoriatic arthritis (PA) underwent HL-A tissue typing. HL-A W27 was significantly increased in psoriatic spondylitis (35%), whereas statistical significance was not reached in patients with peripheral arthritis alone, although W27 was present in a frequency greater than in controls. Psoriatic spondylitis (often asymptomatic) occurred in 57% (23 of 40) of our PA patients. Of interest, psoriatic spondylitis was more often W27 negative than W27 positive; nevertheless, W27-positive and W27-negative spondylitis was clinically and radiographically indistinguishable except that W27-positive disease occurred exclusively in males and the duration of the psoriasis.