Descriptive epidemiology of childhood Langerhans cell histiocytosis in France, 2000-2004.

INTRODUCTION: Childhood Langerhans cell histiocytosis (LCH) is a rare and poorly understood multisystemic disease. The French National Registry of Childhood Hematopoietic Malignancies (NRCH) has recorded LCH cases of all subtypes since 2000. The present study describes the data on LCH collected on a national scale over a 5-year period.

MATERIALS AND METHODS: The cases were children aged less than 15 years, diagnosed with LCH of any type between 2000 and 2004, and residing in mainland France at the time of diagnosis. Completeness was evaluated by capture-recapture after cross-checking against the database compiled by the French Langerhans Cell Histiocytosis Study Group.

RESULTS: Two hundred fifty-eight cases of LCH were registered. The completeness of the NRCH was estimated to be 97%. The annual incidence rate was 4.6/10(6) children aged less than 15 years and the sex ratio was 1.2. Bone and skin were the most commonly involved organs at diagnosis. The incidence rate decreased with age from 15.3/10(6) before 1 year to 2.0/10(6) after 10 years. The disease was mainly unifocal (2.6/10(6)) and rarely disseminated (0.6/10(6)), but disseminated forms predominated in infants. The overall 2-year survival rate was 99% (95%CI: [97; 100]). About 30% of the LCH cases were enrolled in a clinical trial at first onset. No case was treated by radiotherapy.

CONCLUSION: This study evidenced the main features of LCH incidence in the overall population and was consistent with previous studies. The NRCH thus appears to be a very promising tool for further elucidation of LCH.