Pathogenesis of the Sporadic Case of Tuberculosis

PROBABLY every physician has been surprised by the sporadic appearance of pulmonary and other forms of tuberculosis in a previously healthy older person in whom recent exposure to an open case of the infection appeared highly unlikely. Occasionally, active tuberculosis is discovered at autopsy as the cause of an unexplained illness in a person with no apparent source of infection in the environment. When the disease is extrapulmonary (kidney, spine and so forth) it is usually explained as a late progression of a dormant infection. But when it lies within the lung, it is common to invoke reinfection (or superinfection) . . .