Role of the thymus in histiocytosis-X.

An increasing number of reports have demonstrated that patients with histiocytosis-X show significant morphologic changes in the thymus gland. The changes include severe dysplasia, dysmorphia, and severe nonspecific involution. These findings are present in all children with histiocytosis-X who die, but can be found even when the disease is limited to one bone and is not fatal.