A Novel Complete Autosomal-Recessive STAT1 LOF Variant Causes Immunodeficiency with Hemophagocytic Lymphohistiocytosis-Like Hyperinflammation

J Allergy Clin Immunol Pract. 2020 Oct;8(9):3102-3111. doi: 10.1016/j.jaip.2020.06.034. Epub 2020 Jun 27.


Background: Complete signal transducer and activator of transcription 1 (STAT1) deficiency causes a rare primary immunodeficiency that is characterized by defective IFN-dependent gene expression leading to life-threatening viral and mycobacterial infections early in life.

Objective: To characterize a novel STAT1 loss-of-function variant leading to pathological infection susceptibility and hyperinflammation.

Methods: Clinical, immunologic, and genetic characterization of a patient with severe infections and hemophagocytic lymphohistiocytosis-like hyperinflammation was investigated.

Results: We reported a child of consanguineous parents who presented with multiple severe viral infections that ultimately triggered hemophagocytic lymphohistiocytosis and liver failure. Despite intensified therapy with antivirals and cytomegalovirus-specific donor cells, the child died after hematopoietic stem cell transplantation because of cytomegalovirus reactivation with acute respiratory distress syndrome. Exome sequencing revealed a homozygous STAT1 variant (p.Val339ProfsTer18), leading to loss of STAT1 protein expression. Upon type I and type II IFN stimulation, immune and nonimmune cells showed defective upregulation of IFN-stimulated genes and increased susceptibility to viral infection in vitro. Increased viral infection rates were paralleled by hyperinflammatory ex vivo cytokine responses with increased production of TNF, IL-6, and IL-18.

Conclusions: Complete STAT1 deficiency is a devastating disorder characterized by severe viral infections and ensuing hyperinflammatory responses. Early diagnosis can be made by exome sequencing and variant validation by functional testing of STAT1-dependent programmed cell death 1 ligand 1 surface expression on monocytes. Furthermore, high awareness for hyperinflammatory complications and potential targeted treatment strategies such as IL-18 binding protein could be considered. Hematopoietic stem cell transplantation is the only definitive treatment strategy but remains challenging.

Keywords: CXCL10; Hematopoietic stem cell transplantation; Hemophagocytic lymphohistiocytosis; Hyperinflammation; IL-18; LOF; PD-L1; Primary immune deficiency; STAT1.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Child
  • Cytomegalovirus
  • Hematopoietic Stem Cell Transplantation*
  • Humans
  • Immunologic Deficiency Syndromes* / diagnosis
  • Immunologic Deficiency Syndromes* / genetics
  • Lymphohistiocytosis, Hemophagocytic* / diagnosis
  • Lymphohistiocytosis, Hemophagocytic* / genetics
  • STAT1 Transcription Factor / genetics
  • Virus Diseases*


  • STAT1 Transcription Factor
  • STAT1 protein, human