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Pediatr Blood Cancer. 2015 Feb;62(2):346-352. doi: 10.1002/pbc.25308. Epub 2014 Nov 8.

Incidence and clinical presentation of primary hemophagocytic lymphohistiocytosis in Sweden.

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Childhood Cancer Research Unit, Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden.
Clinical Genetics Unit, Department of Molecular Medicine and Surgery, and Center for Molecular Medicine, Karolinska Institutet, Karolinska University Hospital Solna, Stockholm, Sweden.
Department of Women's and Children's Health, University of Gothenburg, The Queen Silvia Children's Hospital, Gothenburg, Sweden.
Centre for Infectious Medicine, Department of Medicine, Karolinska Institutet, Karolinska University Hospital Huddinge, Stockholm, Sweden.
Broegelmann Research Laboratory, Department of Clinical Sciences, Univerisity of Bergen, Bergen, Norway.



Primary hemophagocytic lymphohistiocytosis (HLH) represents a group of inherited hyperinflammatory immunodeficiencies, including familial HLH (FHL), Griscelli syndrome type 2 (GS2), and X-linked lymphoproliferative syndrome (XLP). We previously reported an annual incidence of suspected primary HLH in Sweden 1971-1986 of 0.12 per 100,000 children. Here, we determined if the incidence had increased with concomitant awareness.


Children <15 years old presenting with HLH 1987-2006 in Sweden were identified through the national mortality registry as well as by nation-wide inquiries to all pediatric centers. HLH was diagnosed according to the HLH-2004 diagnostic guidelines (in case of missing data of at least three of the eight diagnostic criteria, fulfillment of four was sufficient for inclusion). We defined primary HLH as patients presenting with HLH requiring transplantation or dying of disease.


Remarkably, the minimal annual incidence rate of primary HLH remained 0.12 per 100,000 children, equating to 1.8 per 100,000 live births. Notably, an increased overall survival was observed in 1997-2006, relative to the period 1987-1996. During the subsequent 5-year period, 2007-2011, the incidence of genetically and/or functionally verified primary HLH was 0.15 per 100,000 children per year, suggesting that new assays may aid the identification of patients with primary HLH.


The annual incidence of primary HLH in Sweden is 0.12-0.15 per 100,000 children per year. Pediatr Blood Cancer 2015;62:346-352. © 2014 Wiley Periodicals, Inc.


cytotoxic lymphocyte; hemophagocytic lymphohistiocytosis; incidence; primary immunodeficiency

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