[Sporadic progressive mucinous histiocytosis]

Progressive mucinous histiocytosis is a very rare, benign, non-Langerhans' cell histiocytosis limited to the skin. This disorder has been observed solely in women, with the exception of three cases in male patients, and most cases are hereditary. The hereditary forms begin in childhood, with sporadic cases occurring later, and it is characterized by numerous papules of slow progression. The aetiology and mode of genetic transmission remain unclear. We report one sporadic case of progressive mucinous histiocytosis.

A 33-year-old woman presented with a 15-year history of multiple small purplish asymptomatic papules on the outside of both legs. There was no history of similar cases in her family. The dermatologists she consulted suggested a diagnosis of lichen planus. A punch biopsy was performed and revealed dermal accumulation of histiocytes with abundant mucin deposition.

Seventeen hereditary cases in seven families, all of which concerned women except for three males, and five sporadic cases have been described to date. The clinical and histological presentation is typical. Histopathology shows dermal accumulation of histiocytes with abundant mucin deposition. The ultrastructural aspect (intracytoplasmic phospholipid deposits) and progressive extension suggest a disorder similar to that observed in lysosomal diseases. However, primary proliferation of macrophages in response to an unknown stimulus cannot be ruled out. At present, there is no treatment.