Short description of the current situation in Langerhans Cell Histiocytosis

Langerhans cell histiocytosis (LCH) and non-Langerhans cell histiocytosis are rare diseases of the mononuclear phagocytic cell system with heterogeneous clinical presentations and unpredictable courses affecting patients of all ages. The annual incidence of LCH is about 0.5 out of 100,000 children under 15 years old. Approximately 400 new cases are diagnosed annually in the EU. Despite a common histopathological definition for LCH several clinical courses are observed. LCH involvement can be limited to skin or bone with an excellent prognosis or extend to the severe multi-system involvement associated with a poor outcome. About a third of patients experience permanent consequences: diabetes insipidus, growth hormone deficiency, liver sclerosing cholangitis, respiratory insufficiency and the neurogenerative cerebellar syndrome. Such permanent consequences, which appear late in the course of the disease, can have significant effects on quality of life and life expectancy.

Many specialists are usually involved in the diagnosis and care of the children, including paediatricians, hemato-oncologists, orthopaedists, endocrinologists, dermatologists, neurologists, pneumonologists, hepatologists, etc. Since treatment often involves chemotherapy, the coordination of clinical networks in different countries is commonly led by paediatric hemato-oncologists. The situation for adults is less well organized.

The associated partners of the Histio Net project have been involved or closely associated to almost all studies in this field in the last 10 years. Their scientific production is available by pubmed.

Both the rarity of LCH, and its multi system presentation, cause a major challenge in conducting clinical trials and collecting comprehensive clinical data. To date, through international collaboration, it has been possible to conduct several clinical trials for patients with advanced disease, representing around 15% of the patients. Studies to prevent the late and devastating consequences of LCH remain to be organised for all patients. This will only be possible by co-ordinating national initiatives through the creation of a histiocytosis network. This project aims at supporting the existing national reference centres for LCH in order to coordinate their work. It also aims at disseminating appropriate recommendations for this extremely rare disease to reinforce the quality of patient care across the EU.

Today, many health care professionals have very limited LCH expertise in diagnosing, treating and counselling. Some centres could follow less than a single patient a year, leading to deleterious practice. And often, clinicians find it extremely difficult to answer questions posed by patients and their families, for example about the clinical course, without using medical jargon.