To study trends in the incidence of juvenile rheumatoid arthritis (JRA) and to obtain information on the incidence of other juvenile rheumatic diseases in Finland.
The present study covered those subjects entitled under the nationwide sickness insurance scheme to receive specially reimbursed medication for juvenile rheumatic diseases in 5/21 central hospital districts in Finland (population base about 270,000 children < 16 years of age) in 1980, 1985 and 1990.
A total of 114 incident cases (34 boys, 80 girls) satisfied the criteria for JRA during the three study years: 1980, 1985 and 1990. Seven of the patients had systemic-onset disease. The incidence of JRA remained similar (14/100,000 in the population < 16 years of age). The female: male ratio was 2.4: 1. Only one case of juvenile spondyloarthropathy was found. Seven patients had juvenile systemic lupus erythematosus and four had juvenile dermato/polymyositis. The corresponding annual incidence rates were 0.1, 0.9 and 0.5/100,000, respectively, in this population.
The present study provides population-based figures on the occurrence of various chronic arthritic syndromes in childhood using a unified data base. The incidence of JRA remained quite similar for the three study years. The incidence figures for systemic rheumatic and connective tissue diseases were slightly higher than those reported in previous studies.