A case of generalized eruptive histiocytosis.

Histiocytoses are a heterogeneous group of diseases, characterized by the accumulation of reactive or neoplastic histiocytes in various tissues. Generalized eruptive histiocytosis belongs to cutaneous non-Langerhans' cell histiocytoses and is a rare, generalized, self-healing disorder that usually follows a benign clinical course. Herein, we report a case of generalized eruptive histiocytosis in a 41-year-old woman with peculiar clinical and histological features. Clinically, the papules showed a marked distribution into the seborrhoeic areas of the trunk, with a great tendency to coalesce. Furthermore, immunohistochemical labelling demonstrated that the histiocytes were positive for CD68, but negative for CD34, S100, CD1a and XIIIa factor. This is the second report of generalized eruptive histiocytosis with a negative XIIIa factor. We discuss the differential diagnoses of the clinical picture and emphasize that this benign cutaneous disorder should be subjected to close follow-up, owing to the possibility of evolution to a more severe type of histiocytosis or the association with underlying diseases. Spontaneous regression was observed in this actual case.