Pulmonary involvement by histiocytosis X in the pediatric age group.

The lungs may be involved by histiocytosis X either as part of a generalized disease or as a separate entity, primary pulmonary histiocytosis X. The former is much more frequent in the pediatric age group, and although it occurs primarily in those who are quite sick with widely disseminated disease, the lung involvement rarely caused symptoms and almost invariably clears. By contrast, primary pulmonary histiocytosis X is mainly seen in young adult males and frequently leads to severe disability. Twelve patients less than 20 years old with lung involvement by histiocytosis X are presented.