[The epidemiology of pulmonary disease caused by Mycobacterium avium complex in Japan]

The number of the patients of active lung tuberculosis and nontuberculous lung mycobacteriosis (NTM) admitted to the 97 sanatoriums in Japan were studied. The number and the prevalence rate of tuberculosis did not decrease during the years from 1985 to 1990, indicating the prevalence rate of 43.1 in 1990 per 100,000 population. Nevertheless, the number of NTM has gradually increased in these 6 years. The prevalence rate of NTM and pulmonary M. avium complex disease (MAC) calculated were 4.18 and 2.46 in 1985, increasing to 6.90 and 4.53 in 1990. Consequently, annual number of the patients newly infected with MAC was suspected to be approximately 5500 in 1990 in Japan. These infections occurred principally in South-West of Japan in the previous years, and were not so common in northern part of Japan. However, a remarkable increase in the number and the prevalence rate of MAC infection has also been noted in northern part of Japan in these 6 years. The number of MAC patients distributed equally in both sexes and the average age was 67 years. The 60% of the patients had some underlying diseases.