A child with both Langerhans and non-Langerhans cell histiocytosis.

The histiocytic syndromes consist of a group of disorders that share in common the proliferation of cells of the monocytic/macrophage lineage. It has been conventional to divide the histiocytoses into two separate groups: Langerhans cell histiocytosis (LCH) and non-LCH. We present a 2-year-old Hispanic boy who was referred to the dermatology clinic for evaluation of an asymptomatic cutaneous eruption of the head and upper trunk. In addition, he had a 3-week history of pain in his right leg and difficulty in walking. The patient's physical examination was normal, excluding the skin findings. On plain radiography, multiple lytic lesions in the skull, lumbar spine, and right tibia were seen. Histopathologic examination of a skin biopsy specimen revealed a predominantly histiocytic infiltrate in the dermis which was negative for S-100 and CD1a stains. A tibial biopsy specimen showed a monomorphous infiltrate of histiocytes that were S-100 and CD1a positive. This patient's concomitant findings of both LCH and non-LCH histiocytoses further support a potential overlap within the histiocytic syndromes, as has been suggested by others.