Other names: Haemophagocytic Lymphohistiocytosis; Haemophagocytic Syndrome; Hemophagocytic Syndrome; HLH

Hemophagocytic lymphohistiocytosis (HLH)  is a life-threatening condition due to overactive cells of the immune system causing excessive inflammation, which results in damage to tissue and organs especially the liver, brain, skin and bone marrow.

There are two types of HLH, primary HLH and secondary HLH.   Primary HLH is a hereditary condition that is also called  familial hemophagocytic lymphohistiocytosis (FHL).   Secondary HLH or acquired hemophagocytic lymphohistiocytosis usually occurs after a substantial immune reaction for example a systemic infection, malignancy or immunodeficiency.

In the immune system when the T cells and NK cells work correctly their job is to destroy damaged or infected cells within the body.  However in HLH there is a decrease in NK cell activity and an increase in T cells, with a resulting increase in cytokines.  This causes an prolonged macrophage activation and inflammatory reactions which results in the extensive tissue and organ damage and symptoms.

Symptoms of HLH are usually rash, fever, enlarged lymph nodes, enlarged liver and spleen, swollen gums and gastrointestinal problems. If HLH is untreated it can progress to multi-organ failure.  Therapy for HLH is aimed at reducing the life-threatening inflammation.

Drugs used to treat Hemophagocytic Lymphohistiocytosis