[Pneumoconiosis and mycobacterial infection].

This symposium was organized to provide recent informations concerning pneumoconiosis and mycobacterial diseases in Japan. Pneumoconiotic workers have been decreasing in number and in severity because of change in industrial structure and improvement of occupational health measures. But radiological figures of dust exposed worker are going to be complex and be difficult for diagnosis due to aging, smoking and of complicated respiratory and non-respiratory diseases. Major complications such as pulmonary tuberculosis and tuberculous pleurisy are decreasing but non-tuberculous mycobacterial infections have become common among dust exposed workers. Dr. Katsuhiro Suzuki (National Kinki-Chuo Hospital) reported pulmonary tuberculosis complicated with pneumoconiosis. A few reports regarding tuberculosis with pneumoconiosis have been published in recent years, particularly in Japan. Thus, clinical characteristics of the cases in our hospital between 1998 and 2003 were summarized here. There were 22 such patients, who consisted of 21 men and one woman and were 49 to 91 years old. There were 19 cases with silicosis, two cases with asbestosis, and one case with siderosis. Bilateral and cavitary lesions in a chest XP were revealed in 82% and 29% of the cases, respectively. Standard chemotherapeutic regimens consisted of three or four drugs with a prolonged period were found to be as effective as that for healthy subjects, judging from the sputum conversion rate after 8 week treatment. Dr. Toshiyuki Yamauchi (Keihai Rosai Hospital) reported, based on autopsy findings, trends in combined-type tuberculosis accompanying pneumoconiosis. The study period was divided into first (1963-1980) and second (1981-2000) stages based on year of patients death. To assess the therapeutic efficacy of antituberculosis agents, patients with combined-type tuberculosis were pathologically divided into those with active tuberculosis and those with inactive tuberculosis. The incidence of active tuberculosis during the second stage was significantly lower than that during the first stage. In both first and second stages, the average age of death for patients with inactive tuberculosis was older than that for those with active tuberculosis. It was shown that active combined-type tuberculosis was resistant to antituberculosis therapy and the prognosis of those patients tends to be poor. But for all patients with active and inactive combined-type tuberculosis, the average age of death was comparable to that of patients without tuberculosis in each stage. The results indicated that the antituberculosis agents were effective to combined-type tuberculosis. Dr. Kiyonobu Kimura (Iwamizawa Rosai Hospital) carried out retrospective studies on some clinico-epidemiologic problems in the cases accumulated in his hospital during the past 49 years. Since his cases consist of various different pathological changes, he has adopted the term "pneumoconiosis complicated with pulmonary tuberculosis" instead of silico-tuberculosis. The results were summarized as follows: (1) The rates of active pulmonary tuberculosis out of 1051 total dead cases were 43.8% (28/64) from 1955 to 1964, 28.8% (62/215) from 1965 to 1974, 24.7% (93/376) from 1975 to 1984, and 10.1% (40/396) from 1985 to 1994. (2) The rates of those who died of pulmonary tuberculosis were 17.2% (11/64) from 1955 to 1964, 9.3% (20/215) from 1965 to 1974, 1.9% (7/376) from 1975 to 1984, and 3.3% (13/396) from 1985 to 1994, respectively. (3) The average age of death of pulmonary tuberculosis has become older and is not significantly different from that of pneumoconiosis patients who died of other cause. (4) The rate of sputum negative conversion was only 9.1% (3/33) during the first 10 years (from 1955 to 1964). On the other hand, 95% (21/22) in the recent 9 years (from 1993 to 2002). (5) Out of the 104 autopsy cases in whom pneumoconiosis and tuberculosis were diagnosed pathologically, 64 cases were combined form of tuberculosis, and other 40 cases were complicated form of tuberculosis. Dr. Hiroki Morita (Asahi Rosai Hospital) studied the nontuberculous mycobacteria (NTM) in the patients with pneumoconiosis and the clinical courses of the 4 types of pneumoconiosis complicated with NTM pulmonary disease. NTM were detected in the 73 (29%) of 252 pneumoconiosis. The 14 species (M. gordonae, M. avium, M. terrae, M. fortuitum, M. nonchromogenicum, M. peregrinum, M. intracellulare, M. szulgai, M. abscessus, M. simiae, M. chelonae, M. scrofulaceum, M. xenopi, M. triviale) were identified. In the long-term follow-up study of the pneumoconiosis patients complicated by NTM pulmonary disease, it was very difficult to catch the onset of NTM pulmonary disease because the clinical signs and symptoms were nonspecific and the radiographic findings moved very slowly. Dr. Mitsunori Sakatani (National Kinki-Chuo Hospital) reviewed the laws related safety and health for dust exposed workers, pneumoconiosis and tuberculosis, and he pointed out importance for prevention, diagnosis, treatment and compensation.