Severe Fever with Thrombocytopenia Syndrome Complicated by Haemophagocytic Lymphohistiocytosis: A Retrospective Cohort Study

Haemophagocytic lymphohistiocytosis (HLH) is an acute and rapidly progressive systemic inflammatory disorder characterized by cytopenia, excessive cytokine production and hyperferritinemia( 1 Al-Samkari H. Berliner N. Hemophagocytic Lymphohistiocytosis. Annual review of pathology. 2018; 13 (DOI): 27-49https://doi.org/10.1146/annurev-pathol-020117-043625 Crossref PubMed Scopus (258) Google Scholar ). The primary form is caused by various mutations with genetic inheritance and is predominantly observed in childhood. Secondary HLH occurs in the presence of an underlying disorder, often reactive to a malignant, infectious, or autoimmune stimulus. Increasing reports indicate that viral infections are a common cause of secondary HLH(1). Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne haemorrhagic fever caused by Dabie bandavirus in the family Phenuiviridae of the order Bunyavirales (formerly SFTS virus, SFTSV). Since its emergence nearly a decade ago, SFTSV has affected a growing number of individual across wider geographic regions in Asia. While most people infected with SFTSV experience mild-to-moderate disease, a subset fall critically ill with poor or even fatal outcomes( 2 Li J.C. Zhao J. Li H. Fang L.Q. Liu W. Epidemiology, clinical characteristics, and treatment of severe fever with thrombocytopenia syndrome. Infect Med (Beijing). 2022; 1 (DOI): 40-49https://doi.org/10.1016/j.imj.2021.10.001 Crossref Scopus (7) Google Scholar ). Previous studies have described HLH as a fatal complication of SFTS, however, these studies mainly report isolated cases without any association analysis performed ( 3 Kim K.H. Lee M.J. Ko M.K. Lee E.Y. Yi J. Severe Fever with Thrombocytopenia Syndrome Patients with Hemophagocytic Lymphohistiocytosis Retrospectively Identified in Korea, 2008-2013. J Korean Med Sci. 2018; 33 (DOI): e319https://doi.org/10.3346/jkms.2018.33.e319 Crossref Scopus (8) Google Scholar , 4 Jung I.Y. Ahn K. Kim J. Choi J.Y. Kim H.Y. Uh Y. et al. Higher Fatality for Severe Fever with Thrombocytopenia Syndrome Complicated by Hemophagocytic Lymphohistiocytosis. Yonsei Med J. 2019; 60 (DOI): 592-596https://doi.org/10.3349/ymj.2019.60.6.592 Crossref Scopus (20) Google Scholar ).