How common is HLH? Which age groups is HLH seen in?

  • Estimated at <1 per 100,000 children under 18
  • Likely to be significantly under-recognised
  • Incidence may be as high as 1 in 2000 adult admissions at tertiary medical centres
  • Traditionally considered a disease of children, particularly those <18 months
  • Adults now comprise up to 40% of cases of HLH:
  • Median age of diagnosis being mid-40s to 50s
  • Cases are even seen above age 70