Histiocytosis X in an elderly patient. Ultrastructure and immunocytochemistry after PUVA photochemotherapy.

The clinical features of a 76-year-old man with histiocytosis X of the Letterer-Siwe type, with extensive skin involvement, are described. The patient's lesions responded dramatically to PUVA-photochemotherapy. Light microscopic, immunocytochemical and immunoelectron microscopic findings, before and after PUVA, are reported. Birbeck granules in phagolysosomes of dermal macrophages indicated uptake of destroyed HX cells. Residual HX cells in the skin and HX cells in a recurring lesion expressed the same membrane antigens as in the primary lesions.