What is it HLH?
Hemophagocytic Lymphohistiocytosis (HLH) is a rare and often fatal syndrome of uncontrolled and ineffective inflammatory response to a certain trigger. It is characterized by excessive proliferation of lymphocytes and macrophages (histiocytes), hence the name “lymphohistiocytosis”. This results in the overproduction of cytokines, responsible for many of the clinical features present in this syndrome.
Familial, or genetic, HLH occurs as a result of a genetic mutation leading to impaired cytotoxic function. There have been several genetic mutations indicated in the development of HLH, including an association with congenital immunodeficiency syndromes, such as Chediak-Higashi, Griscelli and X-Linked Lymphoproliferative Syndromes. This form most often occurs within the first year of life (median age 8 months), with the majority of pediatric cases occurring <2 years of age, but can range from infancy to adulthood.
Acquired HLH occurs in the setting of an underlying condition, such as immunodeficiency, malignancy, or autoimmune disease. When HLH is secondary to a predisposing autoimmune disease, it is referred to as macrophage activating syndrome (MAS). Acquired HLH is the most common cause of this syndrome in adults, but this form can be seen in all ages. Overall, the syndrome is most often triggered by an infectious agent in an otherwise healthy person....Read More