[Nontuberculous pulmonary mycobacteriosis complicated by pleuritis].

Pleuritis is a rare complication associated with nontuberculous mycobacteriosis of the lung and its etiology remains to be clarified. We investigated pleuritis associated with nontuberculous mycobacteriosis of the lung in 304 patients who visited our hospital. Of these, 9 patients (3%) had pleural effusion not attributable to any factor other than pleuritis; these cases were diagnosed as pleuritis. Massive pleural effusion requiring drainage was rare (1 patient, 0.3%) and pleuritis accompanied by pneumothorax was also rare (2 patients, 0.7%). The lung lesions in the patients with pleuritis were often extensive or contained a cavity. All these patients showed infection with Mycobacterium avium complex (MAC). Although it is difficult to diagnose MAC-induced pleuritis, patients with this condition often present with at least 1 of the following signs: the presence of nontuberculous mycobacterium in pleural effusion, a predominance of lymphocytes among the cells detected in pleural effusion, a high adenosine deaminase level, and the disappearance of pleural effusion following treatment. Recognizing these signs may aid the diagnosis of MAC-induced pleuritis.