Sarcoidosis: changing clinical manifestation in Japan.

An increase in the number of patients with sarcoidosis in Japan has been recognized noticed in Japan since the 1960's. Sarcoidosis is a systemic disorder, the lesion of which is characterized as an epithelioid cell granuloma formation stimulated by unknown agents. In Japan, the majority of the patients show thoracic involvement which can easily be detected by annual check-up even when they are asymptomatic. The increase in the numbers became prominant during the 1970's and 1980's. However, as half of the patients were asymptomatic, and 75%of cases recovered, sarcoidosis was not clinically recognized as a serious disease during that period. However, in the 1990's, a substantial numberof these patients developed serious respiratory failure due to pulmonary fibrosis. The reason is that in 5%of the cases who were detected during the 1960's and 1970's the disease progressed within 10-15 years after the onset/detection (1 ). They could be justly evaluated as recipients for lung transplantation. Current issues to be solved are as follows: 1) What are the causative agent(s), 2) Whatpathophysiological processes cause epithelioid cell formation. From the histopathological similarity of the lesions between sarcoidosis and tuberculosis, sar-