Hemophagocytic Lymphohistiocytosis: A Review

Hemophagocytic lymphohistiocytosis (HLH) is a disorder charecterised by immune dysregulation. Though it was underdiagnosed earlier now it is increasingly being diagnosed across the world with better awareness among physicians. “Hypercytokinemia” which is the hallmark of HLH can result in end organ damage and even death in some cases if there is delay in diagnosis. It has a wide array of presentation but commonly presents as fever with organomegaly and bicytopenia. A vast majority of cases are acquired due to secondary causes but primary HLH is also not uncommon which also intern gets triggered by infection as suggested by recent studies. Laboratory parameters like Ferritin, triglycerides and fibrinogen along with bicytopenia/pancytopernia aid in further confirmation of this diagnosis. Bone marrow may or may not show evidence of HLH, Hence absence of involvement should not exclude the diagnosis of HLH. Newer modalities like flow cytometry and genetic analysis have contirbuted for widespread recognition of its pathogenesis and etiology. Like various other emergencies, timely diagnosis remains one of the key stones of its management. Management is largely based on HLH-2004 protocol for secondary cases and almost all cases of primary HLH require Hematopeitic Stem Cell transplantation after initial treatment with HLH 2004 protocol. Recent advances have been made in exploring other modalities of treatment like immunomodulatory agents and monoclonal antibodies (ATG, Alemtuzumab, IFN-y) for resistant/refractory cases to achieve desirable outcomes. Our article aims to summarize the new advances in the diagnosis and management of HLH and also gives comprehensive review of the pathophysiology, clinical observations and modern laboratory methods for HLH diagnosis. Early and prompt recognition remains the gold standard to decrease the mortality related to this condition