Racial and Ethnic Differences in the Incidence of Langerhans Cell Histiocytosis Across the Age Spectrum

Langerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasia with an annual incidence of 5 cases per million children <15 and 1-2 cases per million adults ≥18. Pediatric LCH incidence is known to vary by race/ethnicity; less is known among adults. Therefore, we sought to compare LCH incidence by race/ethnicity in the United States (US) across the age spectrum using data from the US Cancer Statistics (USCS) database. LCH incidence data (2010-2022) were obtained from the USCS database and stratified by age at diagnosis and race/ethnicity. Age was defined as childhood (0-14 years), adolescent/young adult (AYA; 15-39 years), and adult (40+ years); race/ethnicity as non-Hispanic White (NHW), non-Hispanic Black, non-Hispanic Asian/Pacific Islander, non-Hispanic American Indian/Alaska Native, and Hispanic. Age-adjusted incidence rate-ratios (IRRs) and 95% confidence intervals (CIs) were calculated using SEER*Stat. A total of 4,080 childhood, 1,399 AYA, and 1,819 adult incident cases with LCH were identified in the USCS database. Hispanic children experienced significantly higher LCH IRRs compared to NHW children (IRRHispanic_children_0to14=1.16, 95% CI: 1.08-1.24), while Hispanic AYAs and adults exhibited significantly lower IRRs compared to NHWs AYAs and adults (IRRHispanic_AYAs_15to39=0.74, 95% CI: 0.64-0.85; IRRHispanic_adults_40+=0.54, 95% CI: 0.45-0.65). A sub-analysis among childhood cases demonstrated the strongest effects were among Hispanic children aged 1-4 and 5-9 compared to NHW children (IRRHispanic_children_1to4=1.35, 95% CI: 1.20-1.51; IRRHispanic_children_5to9=1.16, 95% CI: 1.01-1.33). Hispanic children, particularly those 1-9 years, experience the highest incidence of LCH; a trend not observed in Hispanic AYAs and adults. These findings suggest differences in LCH etiology across the age spectrum.