A local outbreak of sarcoidosis in Northern Japan.

The annual chest X-ray surveys conducted in Hokkaido during a 5 year period from 1972 to 1976 disclosed that the Furano basin located in a central mountainous district had an extremely high discovery rate of the cases with sarcoidosis. Miniature films sized 70 x 70 mm were ready by two or more sarcoidologists. The cases suspicious of sarcoidosis were requested to attent nearby general hospitals for histological examinations. The number of the cases diagnoses as sarcoidosis were 16 out of about 30000 examinees in the Furano basin, 2 out of about 37000 in Sapporo City, the capital of Hokkaido, and one out of about 100000 in other 7 areas. The Furano basin had a significantly higher rate of discovery than Sapporo City or the other 7 areas. Due to the rural localisation, 6 of the 16 Furano cases were confirmed by biopsies, but the remaining 10 were carefully diagnosed with clinical and laboratory findings as they could not come up to general hospitals. Three of the Furano cases belonged to 3 generations in a family. Even if only the 6 histologically confirmed cases were observed, the rate in Furano is still higher than in the other two districts. Thus an intensive epidemiological investigation has been conducted in this district.