Advances in the management of histiocytic disorders

Childhood histiocytoses span a range of diseases. They can vary from a single, small skin lesion that spontaneously regresses, to a systemic disease leading to multiorgan failure and death. They can be classified into Langerhans cell histiocytosis (LCH), non-Langerhans cell histiocytoses (non-LCHs), haemophagocytic lymphohistiocytoses (HLHs) and histiocyte lineage-related malignancies. The establishment of diagnostic, staging and response criteria for LCH has enabled a series of international randomized clinical trials to be conducted that are the basis of evidence-based treatment. As with non-LCHs, individual cases are often difficult to manage and require expert advice. Familial HLH is an inherited disease in which initial remission can be gained by chemotherapeutic or immunological strategies, but allogeneic stem cell transplant is required for cure. There are a variety of leukaemias and sarcomas that are phenotypically derived from the histiocytic lineage; treatment and outcomes for these are generally similar to those of the wider malignant spectrum.