Hemophagocytic Lymphohistiocytosis: manifestation of an untamed immune system
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EDITORIAL COMMENTARY
Hemophagocytic Lymphohistiocytosis: manifestation of an untamed immune system Narendra Kumar Bagri 1 Received: 12 May 2020 / Accepted: 12 May 2020 / Published online: 26 May 2020 # Dr. K C Chaudhuri Foundation 2020
Hemophagocytic lymphohistiocytosis (HLH) is a hyperinflammatory state secondary to impaired cytotoxicity and resultant cytokine storm, presenting with fever, multi-organ failure, cytopenias, hyperferritinemia and coagulation abnormalities. HLH can either be primary/familial caused by mutations in FHLH (familial HLH) genes or secondary to various infections, malignancy, immunodeficiency or rheumatic diseases; in which it is widely known as macrophage activation syndrome (MAS). The impaired cytotoxicity and aberrant immune activation leading to cytokine storm is the common pathogenic mechanism for all forms of HLH [1]. HLH is a life threatening condition with mortality rates as high as 95% in FHLH and 20–30% in secondary HLH. However, with timely diagnosis and the current immunosuppressive protocols, the mortality rates have optimistically reduced to 40% in FHL and less 10% for MAS [1, 2]. Over the last decade there has been increased awareness about HLH but despite this it likely that only tip of the iceberg is being surfaced as many patients with unremitting fever, systemic inflammation, multi-organ involvement and hyperferritinemia may indeed be having underlying HLH [3]. In the current issue of this Journal, Nandhakumar et al. have published their experience with 52 Indian children with HLH [4]. In the present series, infection associated HLH constituted an important cause of HLH (73%) with dengue being the most common inciting trigger; contrasting to the data from Taiwan where infection associated HLH accounted for 53% of all cases, whereas 24% were secondary to underlying rheumatic disease contrary to 9% in the present series [5]. These differences may be due to variability in referral patterns or the classification criteria used for identifying HLH. The recently proposed criteria including 2016 MAS classification criteria, * Narendra Kumar Bagri [email protected] 1
Division of Pediatric Rheumatology, Department of Pediatrics, All India Institute of Medical Sciences, New Delhi, India
MAS/systemic juvenile idiopathic arthritis (SJIA) [MS] score with a sensitivity 73 and 85% and specificity of 99 and 95% respectively, seems more promising for early detection of MAS in underlying rheumatic disease specially, SJIA [6, 7]. Despite the availability of these classification tools for HLH/ MAS, its diagnosis is challenging and it is important to closely observe for evolving clinical symptoms and trend of laboratory parameters for contemplating the underlying diagnosis. The therapeutic strategies opted by authors include use of various drugs ranging from intravenous immunoglobulins, corticosteroids to complete HLH 2004 protocol. It is intriguing to note that more than half of the children with secondary HLH and 65% of those with dengue, improved with symptomatic management and
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