A sporadic case of progressive mucinous histiocytosis

Hereditary progressive mucinous histiocytosis is a rare autosomal dominant non-Langerhans cell histiocytosis. We describe a sporadic case of this synd rome in a 64-year-old woman who had multiple dark-red dome-shaped papulonod ules located mainly on the back of her hands, forearms and thighs. Light mi croscopy revealed a circumscribed upper dermal aggregate of ovoid or spindl e-shaped histiocytes with abundant mucin deposition. Iron deposits and nume rous mast cells were scattered throughout the tumour but giant cells were r are. Electron microscopy revealed a high number of zebra bodies and myeloid bodies in the cytoplasm of the histiocytes. Immunohistochemistry showed po sitive labelling with alpha-1 antitrypsin, Factor XIIIa and CD68, while CD1 a, CD34 and S100 protein were negative. The differential diagnosis of histi ocytic syndromes is discussed.