Langerhans cell histiocytosis. Coloured frontal and side view X-rays of the ankle of a patient with Langerhans cell histiocytosis (LCH). Lesions (brown) can be seen on the tibia (shin bone). LCH is a disorder of the immune system and is characterised by a great increase in the number of histiocytes, a cell of the immune system. These cells move into bones, causing damage such as the lesions seen here. Symptoms are pain and swelling around the affected bones and also fever and general malaise. LCH is treated with corticosteroids. Many patients recover fully, although some may suffer relapses. The cause of the disease is not known.