A Case of Indeterminate Cell Histiocytosis

Indeterminate cell histiocytosis (ICH) is a rare proliferative disorder of indeterminate cells, which express S-100 and CD68 antigens and show variable reactivity for CD1a, but lack Birbeck granules. ICH has been reported in both adults and children, as solitary or multiple papulonodules with rare extracutaneous involvement. We describe the case of a 2 month-old boy who presented with multiple flesh to brown-colored papules on the face, neck, and trunk. Histologic findings showed an infiltrate of histiocytes on the papillary dermis. The histiocytes were positive for S-100 protein and CD68, but negative for CD1a. Ultrastructural study with transmission electron microscopy showed no Birbeck granules, confirming the diagnosis of ICH. There was no visceral involvement and the cutaneous lesions showed spontaneous regression after 1 monthope