Incidence of psoriatic arthritis in Finland.

Patients with psoriasis have an increased incidence of arthritis. Information on the incidence of psoriatic arthritis (PsA) is sparse. The present study covered those subjects who were entitled under the nationwide sickness insurance scheme to receive specially reimbursed medication for PsA in 5/21 central hospital districts in Finland (population basis approximately 1 million adults) in 1990. A total of 65 incident cases satisfied the concept of PsA. The annual incidence of PsA was 6/100,000 of the adult population (> or = 16 yr of age). The mean age at diagnosis was 46.8 yr. The peak incidence occurred in the 45-54 yr age group. The male to female ratio was 1.3:1. The incidence rate in the present study is in agreement with the sparse former figures, but age-specific incidence figures which have not been published earlier are also presented.