To obtain information on the incidence of rare systemic rheumatic and connective tissue diseases in Finland.
Population-based epidemiological study.
Five out of 21 central hospital districts in Finland (population: about 1 million adults > or = 16 years of age).
Subjects entitled under the nationwide sickness insurance scheme to receive specially reimbursed medication for rare systemic rheumatic or connective tissue diseases in 1990.
Incidence.
A total of 30 incident cases occurred. Nine patients had mixed connective tissue disease, four had systemic sclerosis, four had dermato/polymyositis and one patient had inclusion body myositis; the corresponding annual incidence rates were 8, 4, 4 and 1/million of the adult population. Only one patient had adult Still's disease. The overall annual incidence rate of systemic vasculitides was 9/million of the adult population.
This study provides population-based figures on the incidence of rare systemic rheumatic and connective tissue diseases in Finland.