Jun

23

2022

How is hemophagocytic lymphohistiocytosis (HLH) classified?

By William Aird

  • Primary (genetic) HLH:
    • Mendelian inherited conditions leading to HLH.
    • Rare in adults.
    • Associated with impaired perforin-dependent cytotoxicity of T- and natural killer (NK)-cells.
    • Often triggered by an infection.
  • Secondary (reactive) HLH:
    • Non-Mendelian HLH.
    • Accounts for nearly all of adult cases.
    • May occur in setting of:
      • Infection – accounts for about half of HLH cases in adults.
      • Malignancy – reported in about 40%-70% of adult cases.
      • Autoimmune disease – also called macrophage activating syndrome [MAS] when it occurs in this patient population.
      • Transplantation