Spectrum of clinical disease in pulmonary infection with Mycobacterium avium-intracellulare.

Cases of infection with Mycobacterium avium-intracellulare reported in Milwaukee, Wisconsin, have become more common in recent years, and their incidence--50 cases per year--is now similar to that of tuberculosis. Cases usually occur in middle-aged men with underlying lung diseases, but variations in age, sex, presentation, and severity of disease are wide. Several cases that illustrate pathogenesis and spectrum of disease, from primary, to chronic-active, to healing stages, are presented. The disease tends to run an indolent course in most cases, but extensive disease and unfavorable early course indicate poor prognosis. At a 10-year review, mortality had reached sizable numbers in this aging population with frequent serious underlying problems. Only a small number of these deaths can be attributed directly to mycobacterial disease.