Topic- Hemophagocytic Lymphohistiocytosis: A New Foe
Journal Title: Progressing Aspects in Pediatrics and Neonatology - Year 2018, Vol 1, Issue 2
Abstract
Hemophagocytic lymphohistiocytosis (HLH) is an aggressive and life-threatening syndrome of excessive immune activation. It commonly affects infants from birth to 18 months of age, but the disease can be seen in children and adults of all ages. HLH can occur as a familial or sporadic disorder, and it can be triggered by a variety of events that disrupt immune homeostasis. Prompt recognition of the disease and initiation of treatment is essential for the survival of affected patients [1]. HLH is an aggressive and life threatening syndrome of excessive immune activation.HLH is not a single disease entity but rather a syndrome consisting of clinical signs and laboratory abnormalities that result from the uncontrolled proliferation and activation of cells of the monocyte/macrophage lineage. It is characterized by highly activated lymphocytes and macrophages that infiltrate tissues and produce large amounts of proinflammatory cytokines [1,2]. The term hemophagocytosis describes the pathologic finding of activated macrophages, engulfing erythrocytes, leukocytes, platelets, and their precursor cells; typically seen in bone marrow, spleen and lymph nodes. It can rarely be seen in central nervous system, skin and peripheral blood. This phenomenon is an important finding in patients with HLH. However, it may be absent in initial stages of the disease [3]. PATHOPHYSIOLOGY-Macrophages are antigen presenting cells derived from circulating monocytes; they present foreign antigens to lymphocytes. In HLH, macrophages become activated and secrete excessive amounts of cytokines. This leads to severe tissue damage that can result in organ failure. In HLH, Natural killer (NK) cells and cytotoxic T- lymphocytes (CTLs) fail to eliminate activated macrophages. This results in excessive macrophage activity and highly elevated levels of interferon gamma plus other cytokines. Most patients with HLH also exhibit impaired cytotoxic function of NK cells and CTLs [4]. In addition to increased cytokine production, macrophages can also phagocytize host cells. Hemophagocytosis refers to the engulfment of host blood cells by macrophages. Hemophagocytosis is characterized by the presence of red blood cells, platelets, or white blood cells (or fragments of these cells) within the cytoplasm of macrophages. It can be seen on biopsies of immune tissues (lymph nodes, spleen, liver) or bone marrow aspirates. Hemophagocytosis alone is neither pathognomonic of, nor required for, an HLH diagnosis. CLASSIFICATION-HLH can either be genetic, inherited in an autosomal recessive pattern or it can be acquired due to trigger of various infections, malignancies or rheumatic diseases (MAS). Familial HLH is then further sub-classified as with and without hypopigmentation [5].
Authors and Affiliations
Rohit Vohra, Dr Minakshi
Keywords
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- EP ID EP575617
- DOI 10.32474/PAPN.2018.01.000108
- Views 94
- Downloads 0
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