Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Hemophagocytic lymphohistiocytosis ?
    ### Response:
    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.
    