Toward a better understanding of type I interferonopathies: a brief summary, update and beyond.

BACKGROUNDS: Type I interferonopathy is a group of autoinflammatory disorders associated with prominent enhanced type I interferon signaling. The mechanisms are complex, and the clinical phenotypes are diverse. This review briefly summarized the recent progresses of type I interferonopathy focusing on the clinical and molecular features, pathogeneses, diagnoses and potential therapies. DATA SOURCES: Original research articles and literature reviews published in PubMed-indexed journals. RESULTS: Type I interferonopathies include Aicardi-Goutières syndrome, spondyloenchondro-dysplasia with immune dysregulation, stimulator of interferon genes-associated vasculopathy with onset in infancy, X-linked reticulate pigmentary disorder, ubiquitin-specific peptidase 18 deficiency, chronic atypical neutrophilic dermatitis with lipodystrophy, and Singleton-Merten syndrome originally. Other disorders including interferon-stimulated gene 15 deficiency and DNAse II deficiency are believed to be interferonopathies as well. Intracranial calcification, skin vasculopathy, interstitial lung disease, failure to thrive, skeletal development problems and autoimmune features are common. Abnormal responses to nucleic acid stimuli and defective regulation of protein degradation are main mechanisms in disease pathogenesis. First generation Janus kinase inhibitors including baricitinib, tofacitinib and ruxolitinib are useful for disease control. Reverse transcriptase inhibitors seem to be another option for Aicardi-Goutières syndrome. CONCLUSIONS: Tremendous progress has been made for the discovery of type I interferonopathies and responsible genes. Janus kinase inhibitors and other agents have potential therapeutic roles. Future basic, translational and clinical studies towards disease monitoring and powerful therapies are warranted.

MDA5-Associated Neuroinflammation and the Singleton-Merten Syndrome: Two Faces of the Same Type I Interferonopathy Spectrum.

In 1973, Singleton and Merten described a new syndrome in 2 female probands with aortic and cardiac valve calcifications, early loss of secondary dentition, and widened medullary cavities of the phalanges. In 1984, Aicardi and Goutières defined a phenotype resembling congenital viral infection with basal ganglia calcification and increased protein content in the cerebrospinal fluid. Between 2006 and 2012, mutations in 6 different genes were described to be associated with Aicardi-Goutières syndrome, specifically-TREX1, RNASEH2A, RNASEH2B, RNASEH2C, ADAR, and SAMHD1. More recently, mutations in IFIH1 were reported in a variety of neuroimmunological phenotypes, including Aicardi-Goutières syndrome, while a specific Arg822Gln mutation in IFIH1 was described in 3 discrete families with Singleton-Merten syndrome (SMS). IFIH1 encodes for melanoma differentiation-associated gene 5 (MDA5), and all mutations identified to date have been associated with an enhanced interferon response in affected individuals. In this study, we present a male child demonstrating recurrent febrile episodes, spasticity, and basal ganglia calcification suggestive of Aicardi-Goutières syndrome, who carries the same Arg822Gln mutation in IFIH1 previously associated with SMS. We conclude that both diseases are part of the interferonopathy grouping and that the Arg822Gln mutation in IFIH1 can cause a spectrum of disease, including neurological involvement.

Type I interferonopathies in pediatric rheumatology.

Defective regulation of type I interferon response is associated with severe inflammatory phenotypes and autoimmunity. Type I interferonopathies are a clinically heterogenic group of Mendelian diseases with a constitutive activation of this pathway that might present as atypical, severe, early onset rheumatic diseases. Skin vasculopathy with chilblains and livedo reticularis, interstitial lung disease, and panniculitis are common. Recent studies have implicated abnormal responses to nucleic acid stimuli or defective regulation of downstream effector molecules in disease pathogenesis. As observed for IL1-ß and autoinflammatory diseases, knowledge of the defects responsible for type I interferonopathies will likely promote the development of targeted therapy.

[Type I interferonopathies]. / Interféronopathies de type I.

Type I interferonopathies are a group of Mendelian disorders characterized by a common physiopathology: the up-regulation of type I interferons. To date, interferonopathies include Aicardi-Goutières syndrome, familial chilblain lupus, spondyenchondromatosis, PRoteasome-associated auto-inflammatory syndrome (PRAAS) and Singleton-Merten syndrome. These diseases present phenotypic overlap including cutaneous features like chilblain lupus, that can be inaugural or present within the first months of life. This novel set of inborn errors of immunity is evolving rapidly, with recognition of new diseases and genes. Recent and improved understanding of the physiopathology of overexpression of type I interferons has allowed the development of targeted therapies, currently being evaluated, like Janus-kinases or reverse transcriptase inhibitors.