The pathology and pathophysiology of mycobacterial infections.

Classic tuberculosis is the result of infection with the human strain of Mycobacterium tuberculosis, and atypical tuberculosis is the result of infection with atypical mycobacteria. The pathology and course of the disease depend on the sensitivity of the host. Primary tuberculosis is the first infection in an unsensitized host, and secondary, postprimary, or chronic tuberculosis results from reactivation of previously acquired infection or, rarely, reinfection of a sensitized host. The pathology of infection with M avium-intracellulare in patients with acquired immunodeficiency syndrome (AIDS) is different from that of tuberculosis; formation of noncaseating lesions and a marked macrophage response resemble changes seen in lepromatous leprosy. These infections in patients with AIDS are predominantly extrapulmonary.