A clinicopathological study of histiocytosis X.

Thirty-five cases of histiocytosis X in the National Children's Hospital were clinicopathologically studied. Fourteen cases were categorized in diffuse histiocytosis X, Letterer-Siwe type (DHX), 19 cases in multifocal eosinophilic granuloma (MEG) and 2 cases in unifocal eosinophilic granuloma (UEG). Nine of 14 DHX died, of which 6 died of opportunistic infection due to hypoproteinemia and pancytopenia, and 3 died of pulmonary fibrosis probably due to histiocytic infiltration and resultant lymphedema. Infiltration of histiocytes in the bone marrow, thymus and lungs, in addition to the lymphoreticular organs, was conspicuous in autopsy cases of DHX. Skin biopsy was valuable for diagnosis and the immunostaining with anti-S100 antibody was a good marker to characterize infiltrating histiocytes. Prognostic factors and effects of treatments were also evaluated. Only one of 19 MEG died of opportunistic viral infection, but a longer duration for treatment was usually necessary compared to that for DHX. Pathogenesis of histiocytosis X was discussed in relation to T-zone histiocytes.