Recurrent LCHRecurrent Langerhans cell histiocytosis (LCH) is disease that has recurred (come back) after it has been treated. The disease may come back in the same place or in other parts of the body. It often recurs in the bone, ears, skin, or pituitary gland. LCH often recurs the year after stopping treatment. Recurrent LCH is also called reactivation.