Introduction Langerhans cell histiocytosis (LCH) is a rare disease with diverse clinical courses. Despite improvement in survival outcomes in the recent decades, sequelae of the disease remain a concern. This study aimed to provide information on the long-term outcomes in patients with LCH, particularly on the sequelae and any associated factors.

Method Medical records of patients with diagnosis of LCH and being managed in our centre were retrospectively reviewed. Data on the courses of illness, mortality, intervention, types and time of late events were collected and analysed.

Results 70 patients were included with a mean observation time of 12 years (median 10.7 years, range 1–31.3 years). Sequelae related to LCH were present in 56% (n=39), being more common in multisystem diseases and patients with reactivations. Prevalence of sequelae is as follows: orthopaedic related 27%, diabetes insipidus 19%, growth retardation 13%, cosmetic 10%, neurological 7%, hearing 7%, anterior pituitary hormone deficiency 7%, hepatobiliary 4% and ophthalmological 3%. Neurological sequelae could manifest even 10 years after initial diagnosis of LCH. Reactivations, presence of central nervous system (CNS) risk lesions and treatment with radiotherapy were associated with a higher rate of sequelae. The cumulative incidence of reactivation was 34%. Most reactivations occurred in the first 2.5 years after diagnosis.

Conclusion Sequelae were common after LCH, although some were mild. Neurological sequelae could be particularly severe and debilitating. Vigilant long-term follow-up would be essential for optimising patient outcomes. Further studies on the prevention and treatment of CNS disease of LCH are warranted.