[Histiocytic diseases in childhood and adolescence]

Histiocytic diseases are generally rare with a variable clinical course and variable morphology which often have a peak frequency of occurrence in childhood and adolescence. Histiocytoses are subdivided into Langerhans cell histiocytosis and the so-called non-Langerhans cell histiocytosis, such as juvenile xanthogranuloma, Erdheim-Chester disease and Rosai-Dorfman disease. The most common forms of histiocytosis in childhood are Langerhans cell histiocytosis and juvenile xanthogranuloma. In contrast, forms of histiocytosis which occur more frequently in adulthood, such as Erdheim-Chester disease and Rosai-Dorfman disease are rare in childhood. Some forms of histiocytosis harbor BRAFv600E mutations. In Langerhans cell histiocytosis they have been found in 50-55 % of the cases examined and in Erdheim-Chester disease in up to 100 % of cases. In the remaining forms of histiocytosis (especially juvenile xanthogranuloma and Rosai-Dorfman disease) BRAF mutations could not be detected. A prognostic relevance could not be shown so far; however, in individual cases a mutation analysis of BRAF could provide help in the differential diagnostic considerations or the option of a therapy approach with BRAF inhibitors.