Key Points Reactivations of multisystem Langerhans cell histiocytosis (MS-LCH) are reduced by prolonging initial chemotherapy. The previously high mortality of high-risk (risk-organ–positive) MS-LCH in children has been markedly reduced.

This is the first study of LCH to use an active surveillance method with additional sources of ascertainment. Our incidence is comparable with those in other national reports, although it is likely to be an underestimate as each method may have missed some cases, either diagnosed or undiagnosed.

Langerhans cell histiocytosis is a rare disease. Depending on which organs are involved, the disease may prove rapidly fatal, develop a chronic reactivating but therapy-responsive pattern or resolve spontaneously. Understanding of the pathology of the disease is progressing rapidly, and while clinical trials of standard chemotherapy agents continue, it is likely that novel targeted therapy will become feasible in the next decade. Permanent consequences of the disease are more commoner than generally realised.

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Survival rates improved and there were significant increases in incidence for specific cancers in young adults in the North of England. Further research is required to identify the reasons for changing incidence and to investigate the late effects of treatment among survivors.