TOPICS: Langerhans cells, specialized dendritic cells, APCs, birbeck granules, tennis racquet shaped, CD1a, S100, Langerhans cell histiocytosis, eosinophilic granuloma, letterer siwe disease, hand schuller christian disease, osteolytic lesions, skin rash, purpura, ecchymoses, hepatosplenomegaly, exophthalmos, diabetes insipidus