The pathogenesis of pulmonary and miliary tuberculosis.

Tuberculosis is spread from human to human by airborne transmission; it is not a highly infectious disease. Primary infection remits in 90% of cases and is progressive in the remainder; it is accompanied by lymphohematogenous seeding of many organs, and reactivation may occur as early as three months or many years after initial infection. Primary infection generally confers immunity from subsequent reinfection. The risk of reactivation of tuberculosis is greatest in the year after infection, declining sharply thereafter for most patients. Acute miliary tuberculosis has a distinctive pathogenesis that is different from localized postprimary disease. Miliary tuberculosis may appear in a patient with a normal chest roentgenogram; even in patients with abnormal chest roentgenograms, sputum cultures for acid-fast organisms may be negative. Transbronchial biopsy is the preferred method of diagnosis and prompt initiation of treatment is essential.