Langerhans Cell Histiocytosis (LCH) is a rare disease that primarily affects children. The disease manifests in a variety of ways, ranging from spontaneous regression, to repeated reactivations with the risk of long-term consequences. LCH can affect almost any organ (e.g. skin, bones, lung, liver, spleen, gums, ears, eyes, and/or the central nervous system). 70% of pediatric patients present with single system disease. This means that only one organ is affected. The commonest system involved is bone.  Much less frequent is a severe multisystemic disease with rapid progression.

In some ways, LCH is similar to cancer and can be treated with chemotherapy. Unlike cancer, however, LCH sometimes goes into remission without treatment. Depending on disease site and extension, the physician will decide whether to treat the patient and if yes how to treat the patient.

The disease is so rare, that there was little research into its cause and treatment in the past. Therefore 1987 the Histiocyte Society was founded as an organization that brings together physicians and basic scientists involved in treating patients with LCH in order to accumulate knowledge on the disease and to exchange experience on treating patients with LCH. Besides a much better understanding of the underlying biological reasons of the disease, the Society succeeded in developing uniform treatment plans for individual disease patterns, which has lead to a distinct improvement of the outcome of patients with LCH.