Table 1.

Causes of primary and secondary HLH

Primary HLH (Mendelian inherited conditions leading to HLH) (Table 4)
 Defects in the cytolytic function of cytotoxic T cells and/or NK cells13,46,51
 Defects in inflammasome regulation122,123
Secondary HLH (apparently non-Mendelian HLH)10
 Infections (mainly viruses, such as EBV, HIV, and CMV, but also bacteria, parasites, and fungi)14
 Malignancies (mainly malignant lymphoma)15
 Macrophage activation syndrome in autoinflammatory or autoimmune disorders111
 Other causes (organ or stem cell transplantation; metabolic, traumatic, iatrogenic [immunosuppression, vaccination, surgery, hemodialysis] causes; and, rarely, pregnancy)10,14
  • CMV, cytomegalovirus; EBV, Epstein-Barr virus.