An epidemiological survey of psoriasis in the greater Helsinki area.

A questionnaire survey of all members of the Psoriasis Society of the Greater Helsinki area was carried out during March and April 1984 in order to determine the course of psoriasis. 1517 (85.4%) of the members responded; 1050 of them had psoriasis with skin symptoms only (psoriasis; P) and 400 had also joint symptoms (psoriatic arthritis; PA). In two thirds, the psoriasis had started before the age of 30 years. Skin lesions were more frequent in the PA-group than in the P-group, and more severe in men than in women in both groups. Of the 400 with PA, about 70% had moderate to very severe discomfort in their joints. Most of the patients had experienced their first joint symptoms at the age of 20 to 49 years. In the majority of the patients with PA the skin symptoms begun before the joint symptoms; in 7% the joint symptoms had preceded the skin symptoms; and in 10% both symptoms had begun simultaneously.