A20 Haploinsufficiency Research Articles

A20 haploinsufficiency disturbs immune homeostasis and drives the transformation of lymphocytes with permissive antigen receptors.

Genetic TNFAIP3 (A20) inactivation is a classical somatic lymphoma lesion and the genomic trait in haploinsufficiency of A20 (HA20). In a cohort of 34 patients with HA20, we show that heterozygous TNFAIP3 loss skews immune repertoires toward lymphocytes with classical self-reactive antigen receptors typically found in B and T cell lymphomas. This skewing was mediated by a feed-forward tumor necrosis factor (TNF)/A20/nuclear factor κB (NF-κB) loop that shaped pre-lymphoma transcriptome signatures in clonally expanded B (CD81, BACH2, and NEAT1) or T (GATA3, TOX, and PDCD1) cells. The skewing was reversed by anti-TNF treatment but could also progress to overt lymphoma. Analysis of conditional TNFAIP3 knock-out mice reproduced the wiring of the TNF/A20/NF-κB signaling axis with permissive antigen receptors and suggested a distinct regulation in B and T cells. Together, patients with the genetic disorder HA20 provide an exceptional window into A20/TNF/NF-κB-mediated control of immune homeostasis and early steps of lymphomagenesis that remain clinically unrecognized.

Genetic Mutations Associated With TNFAIP3 (A20) Haploinsufficiency and Their Impact on Inflammatory Diseases.

TNF-α-induced protein 3 (TNFAIP3), commonly referred to as A20, is an integral part of the ubiquitin-editing complex that significantly influences immune regulation, apoptosis, and the initiation of diverse immune responses. The A20 protein is characterized by an N-terminal ovarian tumor (OTU) domain and a series of seven zinc finger (ZNF) domains. Mutations in the TNFAIP3 gene are implicated in various immune-related diseases, such as Behçet's disease, polyarticular juvenile idiopathic arthritis, autoimmune thyroiditis, autoimmune hepatitis, and rheumatoid arthritis. These mutations can lead to a spectrum of symptoms, including, but not limited to, recurrent fever, ulcers, rashes, musculoskeletal and gastrointestinal dysfunctions, cardiovascular issues, and respiratory infections. The majority of these mutations are either nonsense (STOP codon) or frameshift mutations, which are typically associated with immune dysfunctions. Nonetheless, missense mutations have also been identified as contributors to these conditions. These genetic alterations may interfere with several biological pathways, notably abnormal NF-κB signaling and dysregulated ubiquitination. Currently, there is no definitive treatment for A20 haploinsufficiency; however, therapeutic strategies can alleviate the symptoms in patients. This review delves into the mutations reported in the TNFAIP3 gene, the clinical progression in affected individuals, potential disease mechanisms, and a brief overview of the available pharmacological interventions for A20 haploinsufficiency. Mandatory genetic testing of the TNFAIP3 gene should be performed in patients diagnosed with autoinflammatory disorders to better understand the genetic underpinnings and guide treatment decisions.

Autoinflammatory syndromes mimicking Behçet's disease with gastrointestinal involvement: a retrospective analysis.

This retrospective study aimed to investigate the clinical characteristics and genetic findings in paediatric patients with gastrointestinal involvement in Behçet's disease (BD), elucidating the spectrum of autoinflammatory syndromes mimicking BD in this young population. Fifty paediatric patients diagnosed with BD between January 2016 and December 2022, including 24 (48%) with gastrointestinal involvement, underwent comprehensive analysis. Clinical presentations, laboratory examinations, gastrointestinal endoscopy, and genetic tests were conducted, with patients stratified based on genetic results for rigorous comparative clinical analysis. The cohort, with a median age of disease onset at 4.0 years, predominantly manifested with recurrent oral ulcers (100%). Gastrointestinal symptoms were prevalent in 83.3%, with abdominal pain (70%) and haematochezia (16.7%) being notable. Endoscopic evaluations unveiled lesions primarily in the terminal ileum and ileocecal region, with diverse ulcers across various anatomical sites. While 70.8% initially met ICBD criteria, only 41.6% fulfilled new paediatric classification criteria. Genetic analysis in 18 patients unveiled pathogenic variants in 7, with the genetic-positive group exhibiting earlier onset and more atypical symptoms. Noteworthy cases included X-linked deficiency in ELF4, A20 haploinsufficiency, and Majeed syndrome, with two cases revealing chromosomal abnormalities such as trisomy 8 syndrome. Comparative analysis underscored earlier disease onset, heightened inflammatory markers, and distinctive gastrointestinal lesions in the genetic-positive cohort. Identification of monogenic diseases and chromosomal abnormalities resembling BD underscores the imperative of precise diagnosis for tailored treatment and genetic counselling. Expanding genetic screening initiatives holds promise for enhancing our comprehension of the genetic landscape associated with BD.

The Complexity of Being A20: From Biological Functions to Genetic Associations.

A20, encoded by TNFAIP3, is a critical negative regulator of immune activation. A20 is a ubiquitin editing enzyme with multiple domains, each of which mediates or stabilizes a key ubiquitin modification. A20 targets diverse proteins that are involved in pleiotropic immunologic pathways. The complexity of A20-mediated immunomodulation is illustrated by the varied effects of A20 deletion in different cell types and disease models. Clinically, the importance of A20 is highlighted by its extensive associations with human disease. A20 germline variants are associated with a wide range of inflammatory diseases, while somatic mutations promote development of B cell lymphomas. More recently, the discovery of A20 haploinsufficiency (HA20) has provided real world evidence for the role of A20 in immune cell function. Originally described as an autosomal dominant form of Behcet's disease, HA20 is now considered a complex inborn error of immunity with a broad spectrum of immunologic and clinical phenotypes.

A20 Haploinsufficiency: A Systematic Review of 177 Cases

A20 haploinsufficiency is an autoinflammatory disease caused by defective inactivation of the NF-κB pathway. We conducted a systematic literature review of articles reporting patients with TNFAIP3 sequence variants from 2016 to August 2023 following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Data from 177 patients from 65 articles were retrieved (108 women). The principal features were mucosal ulcers (n= 129); fever (n= 93) followed by gastrointestinal (n= 81); skin features (n= 76); autoimmunity (n= 61), including thyroiditis (n= 25) and lupus (n= 16); and joint involvements (n= 54). Five patients had died at the time of publication. In 54 of 63 patients, CRP was significantly elevated during flares, with a median of 51 mg/l. The most commonly used treatment included corticosteroids and nonsteroidal anti-inflammatory drugs (n= 32), TNF blockers (n= 29), colchicine (n= 28), and methotrexate (n= 14). TNFAIP3 variants impacted the ovarian tumor domain in 92 cases and a Zinc finger domain in 68 cases. Geographic origin, reported sex, and variant type significantly impacted phenotype. A better understanding of the wide A20 haploinsufficiency phenotype could facilitate the diagnosis process. Much remains to be elucidated about pathogenesis and treatment to improve outcome in patients with A20 haploinsufficiency.

Efficacy and safety of thalidomide in children with monogenic autoinflammatory diseases: a single-center, real-world-evidence study

BackgroundMonogenic autoinflammatory diseases (AIDs) are rare inflammatory diseases caused by genetic variants. The pathogenesis is complex and treatment options are limited. This study aimed to describe the safety and efficacy of thalidomide in the treatment of monogenic AIDs.MethodsThis was a single-center, single-arm, real-world study. From September 2016 to August 2021, patients with monogenic AIDs who met the inclusion and exclusion criteria were given thalidomide for 12 months. There was a 3-month run-in period before dosing. The efficacy and adverse events were evaluated and recorded every 3 months. After 3 and 12 months of thalidomide treatment, clinical manifestations, disease activity score, inflammatory markers, and background medication adjustments were compared with baseline for efficacy analyses.ResultsA total of 16 patients entered this study, including 3 with Aicardi-Goutières syndrome (AGS), 4 Blau syndrome, 2 chronic infantile neurologic cutaneous articular syndrome (CINCA), 2 A20 haploinsufficiency (HA20), 1 adenosine deaminase 2 deficiency(DADA2), 1 familial Mediterranean fever (FMF),1 tumor necrosis factor (TNF) receptor-associated periodic syndrome (TRAPS), 1 PLCγ2-associated antibody deficiency and immune dysregulation (PLAID), and 1 stimulator of interferon genes-associated vasculopathy with onset in infancy(SAVI). The efficacy rate in the 16 patients after 3-month and 12-month thalidomide treatment in patients was 56.3%. Twelve patients completed the study, the fever improved in all of them, rash improved in 7 patients, and 5 patients stopped using glucocorticoids or other immunosuppressive agents. C-reactive protein was normal in 8 patients and erythrocyte sedimentation rate was normal in 11 patients. Anorexia and nausea occurred in 2 cases, with no other reported drug-related adverse reactions.ConclusionThe largest cohort of monogenic AIDs with the treatment of thalidomide demonstrated that thalidomide can help reduce disease activity and inflammation, reduce the dosage of glucocorticoids, and improve clinical outcomes. Thalidomide is relatively safe in monogenic AIDs.

A critical region of A20 unveiled by missense TNFAIP3 variations that lead to autoinflammation.

A20 haploinsufficiency (HA20) is an autoinflammatory disease caused by heterozygous loss-of-function variations in TNFAIP3, the gene encoding the A20 protein. Diagnosis of HA20 is challenging due to its heterogeneous clinical presentation and the lack of pathognomonic symptoms. While the pathogenic effect of TNFAIP3 truncating variations is clearly established, that of missense variations is difficult to determine. Herein, we identified a novel TNFAIP3 variation, p.(Leu236Pro), located in the A20 ovarian tumor (OTU) domain and demonstrated its pathogenicity. In the patients' primary cells, we observed reduced A20 levels. Protein destabilization was predicted in silico for A20_Leu236Pro and enhanced proteasomal degradation was confirmed in vitro through a flow cytometry-based functional assay. By applying this approach to the study of another missense variant, A20_Leu275Pro, for which no functional characterization has been performed to date, we showed that this variant also undergoes enhanced proteasomal degradation. Moreover, we showed a disrupted ability of A20_Leu236Pro to inhibit the NF-κB pathway and to deubiquitinate its substrate TRAF6. Structural modeling revealed that two residues involved in OTU pathogenic missense variations (i.e. Glu192Lys and Cys243Tyr) establish common interactions with Leu236. Interpretation of newly identified missense variations is challenging, requiring, as illustrated here, functional demonstration of their pathogenicity. Together with functional studies, in silico structure analysis is a valuable approach that allowed us (i) to provide a mechanistic explanation for the haploinsufficiency resulting from missense variations and (ii) to unveil a region within the OTU domain critical for A20 function.

Molecular profile of patients with inborn errors of immunity from Nepal

Background and AimsInborn errors of immunity (IEIs) are increasingly being diagnosed in various regions of the world. There are significant challenges in the diagnosis and treatment of IEIs in resource-limited countries. With the availability of one immunologist and increasing awareness, IEIs are diagnosed with increasing frequency and accuracy in Nepal. IEIs are also being evaluated in children presenting with autoimmune manifestations. We describe the profile of patients diagnosed with IEIs in Nepal during 2020–2022. MethodsRecords of all patients with IEIs who were diagnosed and treated at our tertiary care center in Nepal from August 2020 to April 2022 were analysed. Lead author (DB) has examined and diagnosed all cases. IEIs were diagnosed based on the European Society for Immunodeficiencies (ESID) diagnostic criteria and genetic analysis. ResultsThirty-two patients with IEI (19 boys; 13 girls) and 801 children with autoimmune disorders were diagnosed during the study period. Genetic analysis was done on 18 patients. The diagnostic profile of the patients includes patients with chronic granulomatous disease, X-linked agammaglobulinemia, severe combined immunodeficiency, Job syndrome, selective IgA deficiency, specific antibody deficiency, Wiskott-Aldrich Syndrome, CTLA4 deficiency, IPEX syndrome, IFN-IL12 axis defect, hereditary angioedema, MonoMac syndrome, ARPC1B deficiency, leukocyte adhesion defect, PAPA syndrome, autoimmune lymphoproliferative syndrome, ADA2 deficiency, early-complement deficiency lupus, familial cold auto-inflammatory syndrome, A20 haploinsufficiency, and Blau syndrome. Some patients succumbed before the scope of diagnosis. HSCT is planned for 3 patients. ConclusionsOur is the first report of genetically proven IEIs in Nepal. Logistic constraints coupled with a lack of awareness of IEIs among laity and pediatrician accounted for a missed diagnosis, late diagnosis, and poor outcomes in resource-limited settings. Antimicrobial prophylaxis reduced the incidence of breakthrough infections. The lack of HSCT facilities precludes definitive treatment of many IEIs.

The search for an in vitro model for monogenic Behçet’s disease: the influence of A20 protein on functional cell assays

BackgroundA20 protein, encoded by TNFAIP3, is involved in NF-kB pathway regulation. Mutations in TNFAIP3 can lead to A20 haploinsufficiency (A20HA), an important monogenic etiology of Behçet’s disease (BD). Understanding the effect of A20 in immune cells can help to comprehend BD pathophysiology, and pave the road for functional assays for patients with monogenic NF-κB disorders. MethodsTHP-1 (monocytic), HL-60 (neutrophilic) and Daudi (B-lymphoid) cells were transfected with a GFP-tagged plasmid containing either TNFAIP3 or mutated TNFAIP3-L227X genes. Cells were assessed for A20 protein expression, proliferation rates, phagocytic activity and reactive oxygen species (ROS) production. Flow cytometry was used for all assays. ResultsA20 expression (figure 1) was increased in Daudi-TNFAIP3 cells, compared to Daudi [mean of fluorescence intensity (MFI) 241 vs 295, p < 0.01]; THP-1-TNFAIP3 had higher A20 expression (MFI 1396 vs 1169), not statistically significant. A20 expression was reduced in THP-1-TNFAIP3-L227X (MFI 1169 vs 581, p < 0.05) and HL-60-TNFAIP3-L227X (MFI 572 vs 450, p < 0.05), compared to non-transfected cells. THP-1-TNFAIP3-L227X showed higher phagocytic activity than THP-1 and THP-1-TNFAIP3 (MFI 94748 vs 34039.33 vs 18476; p < 0.001) at baseline and after stimulus (MFI 76265 vs 35835 vs 25379; p < 0.05). Similarly, HL-60-TNFAIP3-L227X cells showed higher phagocytic activity than HL-60 (17480 vs 5862; p < 0.01) at baseline and after stimulus (16869 vs 5482; p < 0.01) (figure 2). Constitutional ROS production by THP-1-TNFAIP3 was higher than THP-1 and TNFAIP3-L227X (MFI 291919 vs 98226 vs 230711; p < 0.001). PMA-induced Ki-67 expression of THP-1-TNFAIP3-L227X was increased compared with THP-1 and THP-1-TNFAIP3 (19184 vs 2434 vs 4463; p < 0.01). Ki-67 expression was lower at baseline for Daudi-TNFAIP3-WT, compared to Daudi (MFI 10250 vs 12310; p < 0.01) (figure 3). [Display omitted] [Display omitted] [Display omitted] ConclusionsReduced expression of A20 in TNFAIP3-L227X cells is relevant, considering previous reports of A20HA did not show a dominant negative effect. THP-1-TNFAIP3-L227X presented higher phagocytic activity, a pattern also observed by neutrophilic cells (HL-60-TNFAIP3-L227X), suggesting a specific mutation-induced phenotype. Decreased THP-1-TNFAIP3-L227X oxidative burst suggests a state of cell exhaustion. Lower Ki-67 expression in THP-1-TNFAIP3 and Daudi-TNFAIP3 cells at baseline reinforces the role of A20 as an NF-κB pathway inhibitor.

A20 is a negative regulator of both NF-κB and JNK signaling following T cell receptor stimulation in humans

Abstract A20 is an NF-κB-induced, dual function ubiquitin editing enzyme that negatively regulates NF-κB signaling induced by TNF and other innate immune receptors, constraining inflammation. Indeed, A20 haploinsufficiency drives a severe autoinflammatory disease in humans. Although A20 serves a similar negative feedback function for T cell receptor (TCR) signaling, the molecular mechanisms utilized and their ultimate impact on human T cell function remain unclear. TCR engagement triggers the assembly of the CARD11-BCL10-MALT1 (CBM) protein complex, a signaling platform that governs the activation of downstream transcription factors including NF-κB and c-Jun. We employed an extensive set of mutant expression constructs to better elucidate how A20 regulates TCR signaling output in Jurkat T cells. Intriguingly, A20 knockout cells showed enhanced, sustained NF-κB and JNK signaling after stimulation, which was reversed upon wild-type (WT) A20 complementation. A20 deubiquitinase function was entirely dispensable for NF-κB and JNK regulation, whereas zinc finger domains that confer E3 ligase activity (ZnF4) and linear ubiquitin-binding capacity (ZnF7) were required. Abolishing MALT1-dependent proteolytic cleavage of A20 did not affect suppressive function, although neither N- nor C-terminal A20 cleavage fragments retained regulatory capacity. We also found that CRISPR-mediated deletion of A20 adversely affects the survival and expansion of primary human T cells. Ongoing studies will determine how A20 deletion affects human T cell effector responses after stimulation, and decipher how dysregulated NF-κB and/or JNK signaling contributes to T cell-intrinsic abnormalities that perturb adaptive immune homeostasis.

Abstract 281: A20 (tnfaip3) Knockdown Protects From Abdominal Aortic Aneurysms By Limiting Extra-cellular Matrix Degradation And Maintaining Aortic Smooth Muscle Cell Mass

Background: Our lab has recently demonstrated that haploinsufficiency of A20/TNFAIP3, a potent anti-inflammatory/NFκB inhibitory gene, protects mice from abdominal aortic aneurysms (AAA) by enhancing TGFβ signaling and modulating smooth muscle cell (SMC) differentiation and apoptosis. Here, we explored the impact of A20 knockdown on TGFβ-mediated SMC proliferation and extra cellular matrix (ECM) degradation, both involved in AAA pathogenesis. Methods: AAA was induced by periadventitial elastase application to the infrarenal aorta of both A20 wild-type (WT) and A20 heterozygous (Het) 10-week-old mice who received 0.2% BAPN in their drinking water. Aortae were harvested 28 days after for immunohistochemistry (IHC) analysis of SMC proliferation and ECM markers. In vitro , human aortic SMC cells (HAoSMC) were transduced with rAd.ShRNA A20 (siA20), resulting in 50-70% A20 knockdown, or control rAd.ShRNA Scramble (siScr). HAoSMC were starved for 24 hours, then treated with TGFβ. Proliferation was analyzed by MTS assay, and cell extracts assayed by Western blot (WB) for cell-cycle markers. Results: A20 haplo-insufficiency protected from AAA formation by: 1) decreasing ECM degradation, as gauged by significantly lower MMP-9 expression (n=3, p&lt;0.01), and 2) promoting vessel wall thickening by increasing SMC proliferation (ki67+ nuclei/vessel wall, n=4, p&lt;0.01). Increased SMC proliferation in Het vs. WT aortae correlated with significantly lower expression of the cell-cycle brake, p21 (p21+ nuclei/vessel wall, n=3-7, p&lt;0.05). Akin mouse aortae, A20 knockdown significantly increased TGFβ-mediated HAoSMC proliferation, assessed by the MTS assay (siA20 vs. siScr, n=5, p&lt;0.05). This associated with significantly higher protein levels of the proliferation regulator phospho-ERK1/2 in siA20 vs. siScr-transduced HAoSMC (WB, n=4, p&lt;0.001). Conclusion: Our findings qualify the protective effect of A20 knockdown against AAA development by preserving ECM integrity and promoting TGFβ-mediated SMC proliferation. These targets of A20 knockdown were validated in HAoSMC, further supporting our pursuit of A20-siRNA based therapies to prevent or limit progression of AAA.

A20 haploinsufficiency caused by loss‐of‐function TNFAIP3 mutation likely leads to progression of antiphospholipid syndrome to marginal zone lymphomas following coronavirus disease 2019 vaccination: A case study

AbstractAntiphospholipid syndrome (APS) is a rare autoimmune systemic disorder. Previously, no report suggests that APS could progress to extranodal marginal zone lymphomas (EMZL). In this study, we met an unusual APS patient with such progression to EMZL. The patients had been diagnosed with APS two years ago and was in a stable condition after regular treatment until his readmission to our hospital and re‐diagnosed with EMZL recently. Coincidentally, we noticed that the patient had been immunized against inactivated COVID‐19 vaccine just 2 days before his readmission. Furthermore, we performed whole‐exome sequencing and identified a heterozygous, new variant in TNFAIP3 (tumor necrosis factor, α‐induced protein 3) which encoded A20 protein, a key molecule controlling NF‐κB signaling. This variation caused a loss of a base A in TNFAIP3 gene at position 443_444, leading to a frameshift mutation and the production of a truncated A20 Lys148fs*67. A20 Lys148fs*67 failed to suppress TNF‐α‐induced NF‐κB activation and might act through haploinsufficiency. Vaccines work by triggering an immune response to a virus or bacterium within the body. A20 negatively regulates NF‐κB signaling to protect immune system from overactivation. In our case, the newly identified mutation in the TNFAIP3 led to the production of a loss‐of‐function A20 Lys148fs*67, which lost the ability to inhibit inflammation. The patient with such a heterozygous mutation, when facing with the “second hit” of COVID‐19 vaccination challenge, might produce excessive amounts of inflammatory cytokines and formed "cytokine storm" duo to A20 haploinsufficiency, eventually leading to the progression from APS to EMZL.

The Expanding Spectrum of Autoinflammatory Diseases

Autoinflammatory diseases are systemic disorders caused by genetic or acquired abnormalities in certain signaling pathways of the innate immune system. Dysregulated activation of the inflammasome, i.e. molecular platforms responsible for the activation of caspase-1 and production of interleukin-1β, causes autoinflammation. Familial Mediterranean fever (FMF), the most common genetic autoinflammatory disease, is characterized by a periodic fever and serositis. The complex and heterogeneous genetic background of Japanese FMF patients, accompanied by potential overlap with other rheumatic diseases, suggests crosstalk between genetic and environmental factors. Recently, FMF has been recognized as being part of a spectrum of autoinflammatory syndromes named pyrin-associated autoinflammatory diseases. The discovery of a new monogenic autoinflammatory disease, A20 haploinsufficiency, may provide novel insights into early-onset Behçet's-like diseases. In contrast, adult-onset Still's disease and Schnitzler's syndrome are acquired autoinflammatory diseases without a monogenic abnormality. Although the concept of autoinflammatory diseases originally applied to monogenic hereditary recurrent fevers, it has been expanded to include non-genetic complex autoinflammatory diseases. Information concerning monogenic autoinflammatory diseases may prove useful for elucidating the molecular mechanisms underlying non-genetic autoinflammatory diseases.

Hematopoietic cell transplantation for monogenic inflammatory bowel disease

The pathogenesis of inflammatory bowel disease (IBD) may include immune dysregulation. About 20% of inborn errors of immunity (IEIs) are related to IBD, and more than 60 IEIs are known to present IBD. Monogenic IBDs include those that are refractory to traditional treatment and can be cured by allogeneic hematopoietic cell transplantation (HCT), making early diagnosis and treatment essential. In this report, we present a series of monogenic IBDs that are relatively frequently found in Japan, such as interleukin (IL)-10/IL-10 receptor deficiency, chronic granulomatous disease, XIAP deficiency, immunodysregulation, polyendocrinopathy, enteropathy, and X-linked (IPEX) syndrome, NEMO deficiency, and A20 haploinsufficiency and will describe the features of each IEI and the indications for HCT.

Assessment of type I interferon signatures in undifferentiated inflammatory diseases: A Japanese multicenter experience.

PurposeUpregulation of type I interferon (IFN) signaling has been increasingly detected in inflammatory diseases. Recently, upregulation of the IFN signature has been suggested as a potential biomarker of IFN-driven inflammatory diseases. Yet, it remains unclear to what extent type I IFN is involved in the pathogenesis of undifferentiated inflammatory diseases. This study aimed to quantify the type I IFN signature in clinically undiagnosed patients and assess clinical characteristics in those with a high IFN signature.MethodsThe type I IFN signature was measured in patients’ whole blood cells. Clinical and biological data were collected retrospectively, and an intensive genetic analysis was performed in undiagnosed patients with a high IFN signature.ResultsA total of 117 samples from 94 patients with inflammatory diseases, including 37 undiagnosed cases, were analyzed. Increased IFN signaling was observed in 19 undiagnosed patients, with 10 exhibiting clinical features commonly found in type I interferonopathies. Skin manifestations, observed in eight patients, were macroscopically and histologically similar to those found in proteasome-associated autoinflammatory syndrome. Genetic analysis identified novel mutations in the PSMB8 gene of one patient, and rare variants of unknown significance in genes linked to type I IFN signaling in four patients. A JAK inhibitor effectively treated the patient with the PSMB8 mutations. Patients with clinically quiescent idiopathic pulmonary hemosiderosis and A20 haploinsufficiency showed enhanced IFN signaling.ConclusionsHalf of the patients examined in this study, with undifferentiated inflammatory diseases, clinically quiescent A20 haploinsufficiency, or idiopathic pulmonary hemosiderosis, had an elevated type I IFN signature.

TNFAIP3 mutation causing haploinsufficiency of A20 with a hemophagocytic lymphohistiocytosis phenotype: a report of two cases

BackgroundA20 haploinsufficiency (HA20) is a newly introduced autosomal dominant autoinflammatory disorder, also known as Behcet’s-like disease. Some of the most common symptoms of the disease are recurrent oral, genital, and/or gastrointestinal (GI) ulcers, episodic fever, musculoskeletal symptoms, cutaneous lesions, and recurrent infections. Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening condition of multi-organ failure due to excessive immune activation. HLH has been reported in a few HA20 patients. Herein, we report two children with the primary presentation of HLH, with a mutation in TNFAIP3, in favor of HA20.Case presentationsOur first patient was a 4-month-old boy who presented with fever, irritability, pallor, and hepatosplenomegaly. Pancytopenia, elevated ferritin, and decreased fibrinogen levels were found in laboratory evaluation. He was diagnosed with HLH and was treated with methylprednisolone and cyclosporine. Two years later, whole exome sequencing (WES) indicated a mutation in TNFAIP3 at NM_001270507: exon3: c.C386T, p.T129M, consistent with A20 haploinsufficiency. Etanercept, a TNF inhibitor, was prescribed, but the parents were reluctant to initiate the therapy. The patient passed away with the clinical picture of cerebral hemorrhage.The second patient was a 3-month-old boy who presented with a fever and hepatosplenomegaly. Laboratory evaluation found pancytopenia, hyperferritinemia, hypoalbuminemia, hypertriglyceridemia, and hypofibrinogenemia. With the establishment of the HLH diagnosis, he was treated with etoposide, dexamethasone, and cyclosporine, and recovered. WES results revealed a heterozygous de novo variant of TNFAIP3 (c. T824C in exon 6, 6q23.3) that leads to a proline to leucine amino acid change (p. L275P). He was treated with etanercept and has been symptom-free afterward.ConclusionsThis report is a hypothesis for developing of the HLH phenotype in the presence of TNFAIP3 mutation. Our results provide a new perspective on the role of TNFAIP3 mutation in HLH phenotypes, but more extensive studies are required to confirm these preliminary results.

The Expanding Spectrum of Autoinflammatory Diseases.

Autoinflammatory diseases are systemic disorders caused by genetic or acquired abnormalities in certain signaling pathways of the innate immune system. Dysregulated activation of the inflammasome, i.e. molecular platforms responsible for the activation of caspase-1 and production of interleukin-1β, causes autoinflammation. Familial Mediterranean fever (FMF), the most common genetic autoinflammatory disease, is characterized by a periodic fever and serositis. The complex and heterogeneous genetic background of Japanese FMF patients, accompanied by potential overlap with other rheumatic diseases, suggests crosstalk between genetic and environmental factors. Recently, FMF has been recognized as being part of a spectrum of autoinflammatory syndromes named pyrin-associated autoinflammatory diseases. The discovery of a new monogenic autoinflammatory disease, A20 haploinsufficiency, may provide novel insights into early-onset Behçet's-like diseases. In contrast, adult-onset Still's disease and Schnitzler's syndrome are acquired autoinflammatory diseases without a monogenic abnormality. Although the concept of autoinflammatory diseases originally applied to monogenic hereditary recurrent fevers, it has been expanded to include non-genetic complex autoinflammatory diseases. Information concerning monogenic autoinflammatory diseases may prove useful for elucidating the molecular mechanisms underlying non-genetic autoinflammatory diseases.

A20 Haploinsufficiency in East Asia.

A20, encoded by the TNFAIP3 gene, is a negative regulator of tumor necrosis factor (TNF)-nuclear factor-κB signaling. It was recently demonstrated that A20 haploinsufficiency (HA20), caused by a heterozygous mutation in the TNFAIP3 gene, can present as an early onset autoinflammatory disease resembling Behçet’s disease (BD). In addition to autoinflammatory symptoms, HA20 was also reported to be associated with autoimmune diseases and immunodeficiency. Because the phenotypes associated with HA20 are broad, with different severities observed even among individuals in the same family with identical mutations, it has been assumed that the symptoms of HA20 may depend on genetic background and environmental factors. In this review, we summarize the characteristics of patients with HA20 in East Asia and compare these with patients in other regions, mainly the USA and Europe. Patients with HA20 in East Asia developed recurrent fever more frequently than patients in other regions, but were less likely to develop typical BD symptoms such as skin rashes and genital ulcers. In addition, patients with HA20 in East Asia had low rates of complication with autoimmune diseases and low autoantibody detection rates. While anti-TNF-α agents were the primary treatments for severe HA20 in East Asia, anti-interleukin-1 agents and Janus kinase inhibitors were also administered in other regions. Future studies will need to establish methods for analyzing the pathophysiology of HA20 and determining optimal treatment strategies for each patient.

Pathergy Phenomenon.

Skin pathergy reaction (SPR) is a hyperreactivity response to needle induced trauma which is characterized by a papule or pustule formation, 24–48 h after sterile-needle prick. It is affected by a wide array of factors, including the physical properties of the needles being used, number of pricks and disease related factors such as male gender, active disease. There is a great variation in reactivity among different populations with very low positivity rate in regions of low prevalence like Northern Europe, and higher prevalance mainly in communities living along the historical Silk Road, like Turkey, China and Middle Eastern countries. SPR is not constant during the disease course, has lost its sensitivity over decades and can be positive in various disorders including Sweet's syndrome, pyoderma gangrenosum, Crohn's diesease, A20 haploinsufficiency, deficiency of IL-1-receptor antagonist and few others. Nevertheless, it is a criteria included into many currently used diagnostic or classification criteria for Behçet's disease. Although, not being fully uncovered yet, available data points to the activation of both innate and adaptive immune system with an inflammatory response mediated by polymorphonuclears and T-cells. In addition to its utility in diagnosis of Behçet's Disease, SPR may serve as a model for investigating the inflammatory pathways involved in the etiopathogenesis of this complex disease.

Clinical characteristics and genetic analysis of A20 haploinsufficiency

PurposeTo evaluate the clinical and genetic characteristics of 3 children with Haploinsufficiency of A20 (HA20). Methods:The clinical and genetic testing data of 3 children with HA20 treated at Capital Institute of Pediatrics (CIP) between August 2016 and October 2019 were retrospectively analysed.ResultPatient 1 presented with arthritis and inflammatory bowel disease, patient 2 presented with axial spinal arthritis and lupus-like syndrome, and patient 3 presented with recurrent oral ulcers, gastrointestinal ulcers, and perianal abscesses. Regarding laboratory tests, patients were found to have elevated white blood cell (WBC) count, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). The CRP and ESR was reported to be high in all the patients. The WBC was reported to be high in patient 1 and 3. Patient 2 was positive for antinuclear antibodies, anti-Sjögren’s syndrome antigen A, dsDNA, rheumatoid factor and Coombs test. Genetic testing showed that all three patients had heterozygous mutation in TNFAIP3 gene. As for the treatment, patient 1 was treated with TNFα antagonist, patient 2 was treated with TNF α antagonist and sulfasalazine, and patient 3 was treated with corticosteroids and thalidomide. Patients 1 and 2 were followed for four and 3 months, respectively. There was an improvement in joint and gastrointestinal symptoms; inflammatory indices and rheumatoid factor (RF) were normal, and dsDNA and Coombs test became negative. Patient 3 was treated at another hospital and showed gradual improvement in oral ulcers and perianal abscesses.ConclusionHA20 is a single-gene auto-inflammatory disease caused by mutation in tumour necrosis factor (TNF)-α-induced protein 3 (TNFAIP3) gene. It may present as Behçet-like syndrome and resemble various other autoimmune diseases as well. Corticosteroids and immunosuppressive agents are effective treatments, and cytokine antagonists can be used in refractory cases. Whole-exome genetic testing should be proactively performed for children with early-age onset or Behçet-like syndrome to achieve early diagnosis and accurate treatment.