What causes Hemophagocytic lymphohistiocytosis ?
What causes hemophagocytic lymphohistiocytosis? There are inherited and non-inherited (acquired) causes of hemophagocytic lymphohistiocytosis (HLH). There are five subtypes of inherited HLH which are designated familial HLH, types 1-5. Each subtype is caused by a change (mutation) in a different gene that helps regulate the immune system. The genetic cause of familial HLH, type 1 is currently unknown. Familial HLH, type 2 is caused by mutations in the PRF1 gene. Familial HLH, type 3 is caused by mutations in the UNC13D gene. Familial HLH, type 4 is caused by mutations in the STX11 gene. Familial HLH, type 5 is caused by mutations in the STXBP2 gene.  All of the genes that cause HLH serve as the instructions for proteins that help destroy or turn off activated immune cells that are no longer needed. Changes in these genes lead to an overproduction of immune cells which results in an excessive immune response and the many signs and symptoms of familial HLH. The acquired causes of HLH include: infection, medications that suppress the immune system, autoimmune diseases, immunodeficiencies, certain types of cancer and/or metabolic diseases.