Normolipemic papular xanthomatosis in erythrodermic atopic dermatitis

We describe papular xanthomatosis that progressively developed in a patient with long-standing erythrodermic atopic dermatitis and normal lipid metabolism and without an associated systemic disease. Light microscopy showed a lobulated aggregate of sometimes foamy histiocytes. Ultrastructurally, these histiocytes contained lipid inclusions and lacked features of Langerhans or epithelioid cells. Other granulomatous skin diseases such as tuberculosis, sarcoidosis, or foreign body granuloma were excluded by histologic study, polarizing microscopic examination, electron microscopy, and microbiologic investigations. Nevertheless, these xanthomas showed an antigen expression pattern similar to that found in noninfectious granulomas (CD1a-, MS-1-, CD11c+, MRP-8/-14+, 25F9+, RM 3/1+/-, CD36(+), indicating that normolipemic papular xanthomatosis may be reactive process and should not be included among the true cutaneous non-Langerhans cell histiocytoses.