An idiopathic variation of Langerhans cell histiocytosis, commonly seen as a non-neoplastic osteolytic lesion of bone. Lesions can be unifocal or multifocal. The disease also presents as chronic inflammation in the soft tissue and can result in painless nodules around the head and neck. Lymphadenopathy is common as are fever, eosinophilia, and bone pain. The skin, lungs, eyes, brain, liver, gastrointestinal tract, and bone marrow may also become involved. Seen in adults, but occurs most often in children and twice as frequently in males. Lesions characteristically contain Langerhans cells with histiocytes, neutrophils, eosinophils, and lymphocytes. Treatments include surgery and chemotherapy.