Pulmonary diseases due to Mycobacterium kansasii in Japan.

In Japan, the rate of pulmonary nontuberculous mycobacteriosis (NTM) (atypical mycobacterial diseases) in the total pulmonary mycobacteriosis is continously increasing, in 1994 it reached 14.0% in newly admitted mycobacteriosis cases in 211 sanatoriums throughout Japan (1), and NTMbecame considered an important chest disease. This increase is mainly dependent uponthe recent rapid decrease of tuberculosis in Japan, but partially on the substantial increase in NTMcases, especially those due Xo Mycobacterium kansasii. Nontuberculous mycobacteria include several species, and M. kansasii holds the second most important position after Mycobacteriumavium complex in Japan. The first Japanese case ofM. kansasii was reported in 1963 by Kawabe et al (2). Prior to 1980, the rate of this infection in total NTMwas only 6% or7%, and the cases were limitedto the Tokyo and Kanagawa areas, but in 1980 the rate increased to over 20% and this infection began to appear in throughout Japan (3). Since 1980, the rate of M. kansasii cases has increased gradually; it reached 27.5% in 1985 and has maintained almost the same level since then (1, 4). The reason for the change in epidemiological status of infection ofM. kansasii is unclear, but in part it depends on the ecological changes in Japan, and in part on the development of methods for identification of the species of mycobacteria.