A case report and literature review of "primary" pulmonary histiocytosis X of childhood.

"Primary" pulmonary histiocytosis X, a well-described entity in young adult males in which pulmonary disease is the overriding site of involvement, is exceedingly rare in children younger than 15 years old. We report a new case in a 2-year-old male and review other reported prepubertal cases. The diagnosis of pulmonary histiocytosis X is based on examination of lung tissue. Langerhans cells containing Birbeck granules, seen by electron microscopy, are virtually pathognomonic of histiocytosis X. These Langerhans cells also react with a monoclonal antibody (OKT6) as well as with antibody to S-100 protein. Based on the lack of consensus for the appropriate treatment of pulmonary histiocytosis X and on our patient's favorable response, we recommend initial therapy with corticosteroids alone, reserving more toxic agents for patients who fail to respond to this initial therapy.