The hemophagocytic lymphohistiocytosis (HLH) family encompasses a spectrum of acquired (secondary) and also congenital (primary) life-threatening hyperinflammatory syndromes.
- Primary congenital or familial HLH is a genetically heterogeneous, hereditary, autosomal recessive, hyperinflammatory syndrome caused by a massively exuberant, sepsis-like, inflammatory response of the immune system with overwhelming activation of T lymphocytes and macrophages. It is based on mutations in genes leading to a disruption of the cytolytic function of NK and T cells. The disease is life threatening.
- Secondary, acquired HLH is a reactive, massively exuberant, sepsis-like, inflammatory reaction of the immune system triggered by different initiators. Causes include various bacterial, viral or mycotic infections. Furthermore, hematopoietic neoplasms of various origins. Cytomegalovirus, Epstein-Barr virus, HIV and COVID-19 are the most common triggers. Autoimmune diseases such as juvenile rheumatoid arthritis or systemic lupus erythematosus can also trigger this hyperinflammatory response.