Possible involvement of group A streptococci in the pathogenesis of psoriatic arthritis.

Bacteria have been implicated in the form of Reiter's syndrome, known as reactive arthritis. If bacteria are important in the related spondyloarthropathy psoriatic arthritis, they may be those comprising skin flora. We found elevated levels of antibody to the streptococcal exotoxin antideoxyribonuclease-B in psoriatic arthritis patients in comparison to patients with psoriasis without arthritis, rheumatoid arthritis, other forms of dermatitis, and normal controls. Patients with peripheral arthritis were more likely than psoriatic spondylitis patients to be antideoxyribonuclease-B positive. Streptococci or streptococcal products may be involved in the pathogenesis of psoriatic arthritis in some patients.