Definition of Hemophagocytic Lymphohistiocytosis (HLH)

Hemophagocytic lymphohistiocytosis: A rare, cancer-like disorder in which both certain types of immune system cells (histiocytes and lymphocytes) start to proliferate and damage body tissues or organs. It can be an inherited condition, or it can occur as a result of immunosuppression (as in organ transplants) or infection. Most patients are young children; signs and symptoms include

• changes in blood cell counts,
• enlarged liver and spleen,
• enlarged lymph nodes, and
• rash.

Treatment is by chemotherapy and in some cases bone-marrow transplantation.

See also histiocytosis.