A Novel Type I Interferon Primed Dendritic Cell Subpopulation in TREX1 Mutant Chilblain Lupus Patients.

Heterozygous TREX1 mutations are associated with monogenic familial chilblain lupus and represent a risk factor for developing systemic lupus erythematosus. These interferonopathies originate from chronic type I interferon stimulation due to sensing of inadequately accumulating nucleic acids. We here analysed the composition of dendritic cell (DC) subsets, central stimulators of immune responses, in patients with TREX1 deficiency. We performed single-cell RNA-sequencing of peripheral blood DCs and monocytes from two patients with familial chilblain lupus and heterozygous mutations in TREX1 and from controls. Type I interferon pathway genes were strongly upregulated in patients. Cell frequencies of the myeloid and plasmacytoid DC and of monocyte populations in patients and controls were similar, but we describe a novel DC subpopulation highly enriched in patients: a myeloid DC CD1C+ subpopulation characterized by the expression of LMNA, EMP1 and a type I interferon- stimulated gene profile. The presence of this defined subpopulation was confirmed in a second cohort of patients and controls by flow cytometry, also revealing that an increased percentage of patient's cells in the subcluster express costimulatory molecules. We identified a novel type I interferon responsive myeloid DC subpopulation, that might be important for the perpetuation of TREX1-induced chilblain lupus and other type I interferonopathies.

Pernio and early SARS-CoV-2 variants: natural history of a prospective cohort and the role of interferon.

Cases of new-onset pernio and recurrences in our cohort align tightly with trends in mean 7-day COVID-19 positivity in Wisconsin and mean temperature in Madison, Wisconsin by month.

Photosensitivity and cGAS-Dependent IFN-1 Activation in Patients with Lupus and TREX1 Deficiency.

The exonuclease TREX1 safeguards the cells against DNA accumulation in the cytosol and thereby prevents innate immune activation and autoimmunity. TREX1 mutations lead to chronic DNA damage and cell-intrinsic IFN-1 response. Associated disease phenotypes include Aicardi‒Goutières syndrome, familial chilblain lupus, and systemic lupus erythematosus. Given the role of UV light in lupus pathogenesis, we assessed sensitivity to UV light in patients with lupus and TREX1 mutation by phototesting, which revealed enhanced photosensitivity. TREX1-deficient fibroblasts and keratinocytes generated increased levels of ROS in response to UV irradiation as well as increased levels of 8-oxo-guanine lesions after oxidative stress. Likewise, the primary UV-induced DNA lesions cyclobutane pyrimidine dimers were induced more strongly in TREX1-deficient cells. Further analysis revealed that single-stranded DNA regions, frequently formed during DNA replication and repair, promote cyclobutane pyrimidine dimer formation. Together, this resulted in a strong UV-induced DNA damage response that was associated with a cGAS-dependent IFN-1 activation. In conclusion, these findings link chronic DNA damage to photosensitivity and IFN-1 production in TREX1 deficiency and explain the induction of disease flares on UV exposure in patients with lupus and TREX1 mutation.

Monogenetic causes of chilblains, panniculitis and vasculopathy: the Type I interferonopathies.

Type I interferonopathies are a clinically heterogeneous group of inherited disorders of the innate immune system characterized by constitutive activation of the type I interferon signaling pathway. Cutaneous vasculopathy, lipodystrophy, interstitial lung disease and brain calcifications are the typical manifestations characterizing affected patients. The pathogenic mechanism commonly underlying these disorders is the abnormal activation of immune pathways involved in recognition of non-self-oligonucleotides. These natural defenses against virus consent humans to survive the infections. Target therapies capable of inhibiting type I interferon signaling pathway seem effective in these patients, albeit with possible incomplete responses and severe side effects.

Familial chilblain lupus due to a novel mutation in TREX1 associated with Aicardi-Goutie'res syndrome.

BACKGROUND: Familial chilblain lupus (FCL) is a rare, chronic form of cutaneous lupus erythematosus, which is characterized by painful bluish-red inflammatory cutaneous lesions in acral locations. Mutations in TREX1, SAMHD1 and STING have been described in FCL patients. Less than 10 TREX1 mutation positive FCL families have been described in the literature. CASE PRESENTATION: Genetic study was performed in a large, nonconsanguineous Chinese family with 13 members over 4 generations affected by chilblain lupus. Whole exome sequencing was performed for the index patient. Significant variant detection was subsequently validated by resequencing using Sanger sequencing in the index patient and other family members. A novel pathogenic mutation TREX1 p.Asp18His was iditified in the index patient. The mutation was present in affected individuals and was absent in non-affected individuals in the familiy. CONCLUSIONS: We present a four-generation Chinese family with FCL caused by a novel heterozygous mutation TREX1 p.Asp18His, which had been reported in a patient with Aicardi-Goutie'res syndrome. This is the first reported Chinese family with FCL based on mutation in TREX1.

Designation of Autoinflammatory Skin Manifestations With Specific Genetic Backgrounds.

"Autoinflammatory disease (AiD)" has first been introduced in 1999 when the responsible gene for the familial Hibernean fever or autosomal dominant-type familial Mediterranean fever-like periodic fever syndrome was reportedly identified as tumor necrosis factor receptor superfamily 1. Linked with the rapid research progress in the field of innate immunity, "autoinflammation" has been designated for dysregulated innate immunity in contrast to "autoimmunity" with dysregulated acquired immunity. As hereditary periodic fever syndromes represent the prototype of AiD, monogenic systemic diseases are the main members of AiD. However, skin manifestations provide important clinical information and there are even some AiDs originating from skin diseases. Recently, AiD showing psoriasis and related keratinization diseases have specifically been designated as "autoinflammatory keratinization diseases (AiKD)" and CARD14-associated psoriasis and deficiency of interleukin-36 receptor antagonist previously called as generalized pustular psoriasis are included. Similarly, a number of autoinflammatory skin diseases can be proposed; autoinflamatory urticarial dermatosis (AiUD) such as cryopyrin-associated periodic syndrome; autoinflammatory neutrophilic dermatosis (AiND) such as pyogenic sterile arthritis, pyoderma gangrenosm, and acne syndrome; autoinflammatory granulomatosis (AiG) such as Blau syndrome; autoinflammatory chilblain lupus (AiCL) such as Aicardi-Goutieres syndrome; autoinflammatory lipoatrophy (AiL) such as Nakajo-Nishimura syndrome; autoinflammatory angioedema (AiAE) such as hereditary angioedema; and probable autoinflammatory bullous disease (AiBD) such as granular C3 dermatosis. With these designations, skin manifestations in AiD can easily be recognized and, even more importantly, autoinflammatory pathogenesis of common skin diseases are expected to be more comprehensive.

Assessment of Clinical Response to Janus Kinase Inhibition in Patients With Familial Chilblain Lupus and TREX1 Mutation.

Importance: Familial chilblain lupus is a monogenic autosomal dominant form of cutaneous lupus erythematosus that in most cases is caused by mutations in the 3 prime repair exonuclease 1 (TREX1). Familial chilblain lupus presents in early childhood with cold-induced painful erythematous infiltrates leading to mutilation and is associated with systemic involvement illustrated by an elevated type I interferon (IFN) signature in the skin and blood. Effective treatment is currently not available. Objectives: To evaluate the clinical response to the Janus kinase inhibitor baricitinib in familial chilblain lupus and assess the effect of cold on patient fibroblasts. Design, Setting, and Participants: In this case series, 3 patients with familial chilblain lupus due to TREX1 mutation underwent treatment with baricitinib for 3 months. Interventions: Doses of baricitinib, 4 mg, were administered daily for 3 months. Main Outcomes and Measures: Reduction of cutaneous lupus lesions was measured by the revised cutaneous lupus area and severity index, pain due to skin and joint involvement was assessed by visual analog scale, type I IFN signature in blood was determined by polymerase chain reaction, and the in vitro response of fibroblasts to cold exposure was analyzed. Results: All 3 patients (2 women and 1 man; mean [SD] age, 51 [24] years) showed a significant improvement of cutaneous lupus lesions with suppression of systemic type I IFN activation. One patient had a complete remission regarding pain and, in 2 patients, pain associated with joint inflammation was partially reduced. No severe adverse reactions were reported. Exposure of patient fibroblasts to cold induced a stress response and enhanced senescence along with induction of IFN-stimulated gene in vitro. Conclusions and Relevance: These findings demonstrate the therapeutic efficacy of Janus kinase inhibition in a monogenic form of lupus among 3 patients and provide mechanistic insight into the process of disease exacerbation by cold in TREX1-deficient cells. This finding may be relevant to other type I IFN-mediated disorders and implicates Janus kinase inhibition as a potential therapeutic option also for multifactorial cutaneous lupus erythematosus.

TREX-1-Related Disease Associated with the Presence of Cryofibrinogenemia.

PURPOSE: Cryofibrinogenemia is a rare cryopathy presenting as acrocyanosis following exposure to cold. Familial presentation has been described but the underlying molecular cause remained undetermined. METHODS: Forty (40) members from a large family with an initial diagnosis of familial cryofibrinogenemia were interviewed and examined to determine affected status and collect DNA. Exome sequencing was performed on three affected individuals from distinct branches of the pedigree. RESULTS: Seventeen (17) family members reported a history of acrocyanosis with cold exposure. None reported symptoms were suggestive of lupus. Exome sequencing of three subjects identified the heterozygous mutation D18N in the TREX1 gene which was then confirmed by Sanger sequencing in all affected as well as 2 unaffected family members. The mutation is already being associated with familial chilblain lupus erythematosus (CHLE), and a systematic review of literature was undertaken to compare reports of familial CHLE and cryofibrinogenemia. Both entities were found to share highly similar clinical presentations suggesting they are part of a same syndrome in which cryofibrinogenemia and lupus manifestations have variable penetrance. CONCLUSIONS: Familial cryofibrinogenemia without lupus should be added to the spectrum of TREX1-related disease.

[Familial chilblain lupus: Four cases spanning three generations]. / Lupus-engelures familial : quatre cas sur trois générations.

BACKGROUND: Familial chilblain lupus is a hereditary form of cutaneous lupus erythematosus seen in young children. It shows autosomal dominant inheritance due to mutations in the TREX-1 gene, or, more rarely, SAMHD1 or TMEM173 (STING). It belongs to the type I interferonopathies, i.e. inflammatory diseases associated with excessive interferon production and characterized by a positive "interferon signature". This is a rare entity with fewer than 10 families described to date. We report a new family followed over several years. PATIENTS AND METHODS: The patients were four subjects from the same family and spanning three generations (a brother and sister aged 17 and 15 years, their 39-year-old mother, and their 60-year-old grandfather). The initial cutaneous lesions on the extremities were described as papular, erythematous, purplish, infiltrated, hyperkeratotic, pruritic and/or painful. They occurred in childhood, improved during summer and stabilized over time. Immunological abnormalities such as positive antinuclear antibodies were noted. The interferon signature was positive in all patients. Molecular analysis of TREX-1, SAMHD1 and STING genes in both children showed no evidence of mutation. DISCUSSION: The cutaneous involvement was classic except for absence of the scarring and mutilating progression, photosensitivity and vasculopathy reported in other families. There was no intrafamily variability other than unconstant immunological abnormalities. At the molecular level, no mutations in the known genes were identified. A complementary molecular analysis is in progress. CONCLUSION: We report a new case of familial LEF, thus adding to knowledge about this very rare form of lupus erythematosus.

A homozygote TREX1 mutation in two siblings with different phenotypes: Chilblains and cerebral vasculitis.

Three prime repair exonuclease 1 degrades single and double stranded DNA with 3'-5' nuclease activity and its mutations are related to type 1 IFN mediated autoinflammation due to accumulated intracellular nucleic acids. To date, several cases of systemic lupus erythematosus, Aicardi-Goutieres syndrome, familial chilblain lupus, retinal vasculopathy-cerebral leukodystrophy have been reported with TREX1 mutations. Chilblain lupus is a skin disease characterized by blue-reddish coloring, swelling or ulcers on acral regions of body such as fingertips, heels, nose and auricles. Central nervous system vasculitis is a prominent cause of childhood strokes. 10 families with familial chilblain lupus related to TREX1 mutations were reported previously in the literature, in which homozygote D18N variant in TREX1 gene was related to chilblains with cerebral vasculitis. In this report, whole-exome-sequencing revealed a homozygote R114C mutation in TREX1 gene was shown in two siblings with recurrent chilblains whom one of them was the second case accompanied by cerebral vasculitis in the literature. As a result, the approach of WES in clinical use revealed a novel mutation in clinically heterogenous patients to provide genetic counseling.

Methods of Assessing STING Activation and Trafficking.

The signaling adapter protein STING is crucial for the host immune response to cytosolic DNA and cyclic dinucleotides. Under basal conditions, STING resides on the endoplasmic reticulum (ER ) , but upon activation, it traffics through secretory pathway to cytoplasmic vesicles, where STING activates downstream immune signaling. Classical STING activation and trafficking are triggered by binding of cyclic dinucleotide ligands. STING signaling can also be activated by gain-of-function mutations that lead to constitutive trafficking of STING. These gain-of-function mutations are associated with several human diseases such as STING-associated vasculopathy with onset in infancy (SAVI), systemic lupus erythematosus (SLE), or familial chilblain lupus (FCL). This dynamic activation pathway presents a challenge to study. We describe methods here for measuring ligand-dependent and ligand-independent activation of STING signaling in HEK293T cells. We also describe a retroviral-based reconstitution assay to study STING protein trafficking and activation in immune competent cells such as mouse embryonic fibroblasts (MEF), which avoids the use of plasmid DNA. These methods will expedite research regarding STING trafficking and signaling dynamics in the settings of infection and autoimmune diseases.

Familial Chilblain Lupus - What Can We Learn from Type I Interferonopathies?

PURPOSE OF REVIEW: Familial chilblain lupus belongs to the group of type I interferonopathies and is characterized by typical skin manifestations and acral ischaemia. This review aims to give an overview of clinical signs and the pathophysiological mechanisms. RECENT FINDINGS: There are several mutations that can lead to this autosomal dominant disease. Most frequent is a mutation of the gene for TREX-1. However, as well cases of families with mutations in the SAMHD1 gene and, recently, with one for the gene that codes for the protein stimulator of interferon genes have been described. These genes are involved in the process of the detection of intracellular DNA, and their mutation results in an increased production of type I interferons and their gene products, resulting in auto-inflammation and auto-immunity. JAK inhibitors have been successfully used to treat this disorder. Familial chilblain is a rare disorder with very distinct clinical signs. Its pathophysiological mechanism gives insight into the process of interferon-induced inflammation in auto-immune diseases.

Aicardi-Goutières syndrome: unusual neuro-radiological manifestations.

Aicardi-Goutières syndrome (AGS) is one of the expanding group of inherited congenital infection like syndromes. Here, we describe the detailed clinical and imaging findings of two sibs with AGS. Each shows scattered periventricular intracranial calcifications, severe global delay, seizures, microcephaly and spasticity. Interestingly, chilblains were observed in the two sisters as well as their parents and a paternal uncle. The brain MRI of the older sister showed marked ventricular dilatation as a result of unusual associated porencephalic cysts. Unexpectedly, unilateral cerebellar hypoplasia was also noted. In comparison, her younger sister displayed the classic atrophic changes and white matter loss of AGS. The diagnosis of AGS was confirmed by sequence analysis, which identified a previously reported homozygous RNASEH2B mutation, c.554 T > G (p.V185G). Parents were heterozygous for the same mutation. Further molecular analysis excluded mutations in potentially related manifestations of COL4A1 gene. This is the first report of chilblains associated with heterozygous RNASEH2B mutation. Further, the brain imaging findings appear particularly interesting, which until now has not been reported in any AGS patient. We discuss the possible reasons for this unusual presentation.

Familial chilblain lupus due to a gain-of-function mutation in STING.

OBJECTIVES: Familial chilblain lupus is a monogenic form of cutaneous lupus erythematosus caused by loss-of-function mutations in the nucleases TREX1 or SAMHD1. In a family without TREX1 or SAMHD1 mutation, we sought to determine the causative gene and the underlying disease pathology. METHODS: Exome sequencing was used for disease gene identification. Structural analysis was performed by homology modelling and docking simulations. Type I interferon (IFN) activation was assessed in cells transfected with STING cDNA using an IFN-ß reporter and Western blotting. IFN signatures in patient blood in response to tofacitinib treatment were measured by RT-PCR of IFN-stimulated genes. RESULTS: In a multigenerational family with five members affected with chilblain lupus, we identified a heterozygous mutation of STING, a signalling molecule in the cytosolic DNA sensing pathway. Structural and functional analyses indicate that mutant STING enhances homodimerisation in the absence of its ligand cGAMP resulting in constitutive type I IFN activation. Treatment of two affected family members with the Janus kinase (JAK) inhibitor tofacitinib led to a marked suppression of the IFN signature. CONCLUSIONS: A heterozygous gain-of-function mutation in STING can cause familial chilblain lupus. These findings expand the genetic spectrum of type I IFN-dependent disorders and suggest that JAK inhibition may be of therapeutic value.

The importance of chilblains as a diagnostic clue for mild Aicardi-Goutières syndrome.

Aicardi-Goutières syndrome (AGS) is classically characterized by early-onset encephalopathy. However, in some cases, the presenting symptom of concern may actually be cutaneous rather than neurological, leading to the misdiagnosis of the condition. We report the case of three teenage siblings who presented with a lifetime history of chilblain lesions, only one of whom had notable neurologic deficits. Additional findings included acrocyanosis, Raynaud's phenomenon, low-pitch hoarse voice, headache, and arthritis. They were found to have two pathogenic sequence variants in the SAMHD1 gene: a c.602T>A substitution resulting in p.Ile201Asn protein change, previously reported as a pathogenic mutation, as well as a deletion c.719delT which has not been previously reported but results in a predicted pathogenic frame shift mutation. It is important to consider the diagnosis of AGS in patients and families with chilblain lesions in the presence of unexplained neurologic and rheumatic symptoms. © 2016 Wiley Periodicals, Inc.

Phenotypic familial aggregation in chronic chilblains.

BACKGROUND: Our clinical observations and two earlier studies indicate familial clustering to be involved in chronic chilblains. Demonstrating phenotypic familial aggregation is a next step to investigate the origin of familial clustering. OBJECTIVE: This study was initiated to assess evidence for phenotypic familial aggregation in chronic chilblains. METHODS: Using a case-control family design in a primary care setting, we computed the familial relative risk of at least one episode of chronic chilblains during life with 95% confidence intervals (CIs). The study population consisted of 192 relatives of 31 case probands (at least one confirmed episode of chronic chilblains). The control population consisted of 178 relatives of 31 sex- and age-matched index controls (no history of chronic chilblains). RESULTS: The familial relative risk of chronic chilblains was 3.6 (95% CI 1.9-7.3). Additional sensitivity analysis shows similar figures. CONCLUSION: We demonstrate robust phenotypic familial aggregation in chronic chilblains.