progressive pulmonary tuberculosis

Progressive pulmonary tuberculosis may ensue in the elderly and immunosuppressed. The apical lesion enlarges with expansion of the area of caseation. Erosion into a bronchus evacuates the caseous center, creating a ragged, irregular cavity lined by caseous material that is poorly walled off by fibrous tissue.

Erosion of blood vessels results in hemoptysis. With adequate treatment, the process may be arrested, although healing by fibrosis often distorts the pulmonary architecture. Irregular cavities, now free of caseation necrosis, may remain or collapse in the surrounding fibrosis.

If the treatment is inadequate or if host defenses are impaired, the infection may spread by direct expansion via dissemination through airways, lymphatic channels, or the vascular system.