Pulmonary tuberculosis in children.

TB is no longer the scourge it once was, but it remains an important cause of morbidity and mortality worldwide. Fueled by increasing poverty, homelessness, immigration, drug abuse, declining prevention programs, and the HIV epidemic, its incidence in the United States has increased dramatically. The complex natural history of pulmonary TB in children is reflected in its varied radiographic manifestations. Strict distinction between "adult" and "childhood" patterns of TB should be avoided (Fig 16). In general, adenopathy is the footprint of childhood primary pulmonary TB, with or without a readily apparent primary parenchymal focus or pleural effusion. Infants and young children are more likely to present with adenopathy only than their older counterparts. The pediatric tracheobronchial tree is particularly susceptible to compression by surrounding nodes, producing segmental atelectasis, or less commonly, obstructive emphysema. Self-limited lymphohematogenous dissemination is the rule, but actual miliary disease is the exception. Pediatric postprimary TB, when it occurs, is usually observed in adolescents. It is characterized by parenchymal disease with an anatomic bias for the upper lung zones. Proper image interpretation is inextricably dependent on an understanding of the pathogenesis of this fascinating and often baffling illness whose appearance widely varies depending on host age and immunity as well as the virulence of the organism itself.