Primary pulmonary histiocytosis-X.

SUMMARY Primary pulmonary histiocytosis-X is a disease of the young that is characterized by granulomas formed by histiocytosis-X cells, eosinophils, macrophages, and varying numbers of lymphoid cells. Histiocytosis-X cells are similar to Langerhans' cells and are characterized by intracytoplasmic X-bodies on ultrastructural studies. An immune or hypersensitivity cause of histiocytosis-X is suspected. Clinically, patients most often present with cough and exertional dyspnea. On presentation the chest roentgenogram usually shows a diffuse nodular or reticulonodular infiltrate with relative sparing of the bases and costophrenic angles. Advanced disease is characterized by upper lobe coarsely reticular pattern with cystic lesions typical of a honeycomb lung. Current data indicate that primary pulmonary histiocytosis-X is a relatively benign disease with low mortality and a high rate of spontaneous remission. Although corticosteroids have been used extensively in the past, data on their efficacy are lacking. I would recommend the use of corticosteroids in patients who have moderate to severe symptoms or physiologic abnormalities. If, however, their benefits cannot be documented, they should be discontinued.