A case of S-100-negative CD1a-positive indeterminate cell histiocytosis.

Histiocytoses are a group of rare disorders characterized by a proliferation of monocytes/macrophages and dendritic cells. We present a case of a 3-year-old girl with a diffuse papular eruption without systemic symptoms demonstrating a proliferation of strongly CD1a ⁺ histiocytes, but negative for S-100 and langerin on histopathology. Systemic work-up including bone marrow biopsy was unremarkable, and the patient received a diagnosis of CD1a ⁺ S ^- 100-indeterminate cell histiocytosis.
(© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)