Psoriatic arthritis. Follow-up study.

227 patients with psoriasis and various forms of arthritis have been kept under review. Psoriasis and inflammatory arthropathy was present in 168 patients, of whom 94 have been followed up for more than 10 years. An arthritis indistinguishable from rheumatoid disease was present in 78%, distal joint arthritis in 16-6%, and deforming arthritis in 4-8%. There was a female predominance in the sex ratio of patients, although males predominated in the distal joint group (male:female 1-5:1). The peak age of onset was between 36 and 45 years, although in the deforming group the arthritis began before the age of 20 three times as commonly as it did in the indistinguishable group. Onset was acute in nearly half of the patients. At onset the distal joints were affected in one-third of the distal joint group. A synchronous onset of skin and joint changes was uncommon. Skin lesions usually preceded the arthritis but occurred after onset in 16%. Apart from in the deforming group, the arthritis was mild, judged by the number of admissions to hospital for treatment of the joint disease, and the time off work. Deterioration clinically and radiographically occurred in only a small portion of the distal joint and indistinguishable groups. Antimalarial drugs have been used in 7 patients, with deterioration of the skin condition in 4. Uveitis occurred particularly in the men of all three groups, but was most frequent in those with deforming arthritis. A family history of psoriasis was obtained in 26% of first-degree relatives and 13% of second-degree relatives. A history of polyarthritis was most common in patients in the deforming group. The sheep cell agglutination test was negative in the majority, but was positive in 16% of the indistinguishable group, fluctuating in a further 10%. A small number of joints only deteriorated radiographically (10% of the distal and indistinguishable groups). The men in the distal group showed greater radiographic changes and more deterioration in the terminal interphalangeal joints of the fingers than the women. Similarly they showed more deterioration of the metatarsophalangeal joints than the women. 18 patients died, one with gastric haemorrhage resulting from treatment of exfoliative psoriasis with immunosuppressive therapy, and 2 from bronchopneumonia thought to be related to immobility caused by the arthritis.