Obstructive granulomatous bronchiolitis due to Mycobacterium avium complex in an immunocompetent man.

While the development of pulmonary disease due to Mycobacterium avium complex (MAC) infection is most commonly associated with underlying predisposing factors, this organism occasionally causes symptomatic disease in otherwise normal individuals. Patients with MAC pulmonary disease most often present with cavitating granulomas, but a spectrum of pathologic changes has been described. The authors present a case of MAC pulmonary disease in an immunocompetent, middle-aged man with no identified predisposing factors. The diagnostic biopsy disclosed the unusual finding of noncaseating granulomas with predominant involvement of bronchioles, corresponding to the patient's obstructive and restrictive pulmonary dysfunction.