Histiocytosis X of the skin in an elderly man

A 76 yr old man had a papular erythematous rash, limited to his trunk, of 6 mth duration. Light microscopy revealed dense infiltration of the papillary dermis and overlying epidermis by histiocytic cells characterized by oval and reniform nuclei, nucleoli, and ill defined abundant eosinophilic cytoplasm. Mitotic figures were uncommon. Admixed with the histiocytic infiltrate were occasional lymphocytes and rare plasma cells and polymorphonuclear leukocytes. Eosinophils were not identified. Electron microscopy revealed characteristic Langerhans granules within the cytoplasm and contiguous with the plasma membrane of many of the infiltrating histiocytic cells. Skeletal films during life and autopsy studies failed to reveal any extracutaneous involvement. The findings are reminiscent of the cutaneous lesions seen in Letterer Siwe disease and diagnostic for histiocytosis X. The absence of extracutaneous involvement and the age of the patient are distinctly unusual, but not unprecedented. Adult forms of histiocytosis X showing both limited and diffuse organ involvement have been described. The finding of the Langerhans cell with its characteristic granules provides both a probable cell of origin and unifying feature for this disease complex.