Three Chinese pedigrees of A20 haploinsufficiency: clinical, cytokine and molecular characterization

A20 haploinsufficiency diagnosis beyond systemic lupus erythematosus: A systematic review of the literature

Systemic lupus erythematosus (SLE) is an autoimmune disease whose pathophysiology remains incompletely understood, involving genetic and epigenetic factors. However, an increasing small subset of patients present with monogenic lupus, providing insight into the pathogenesis of the disease. This systematic review focuses on SLE associated with A20 haploinsufficiency (HA20), a monogenic disorder associated with tumor necrosis factor alpha-induced protein 3 gene (TNFAIP3) variants. Besides the mainly auto-inflammatory phenotypic expression of HA20 mimicking Behçet's disease spectrum, some of its clinical and biological manifestations are part of the spectrum of autoimmune diseases, including glomerulonephritis as well as the frequent presence of antinuclear antibodies, sometimes with anti-DNA specificity. Among all the 191 HA20 patients reported in the literature, we identified 16 patients (8.4 %) with a compatible diagnosis of SLE. When estimable, the SLICC 2012 and EULAR/ACR 2019 classification criteria were positive for 92.9 % of them. A majority had multi-system involvement, mainly cutaneous (81.3 %), musculoskeletal (56.3 %), and/or renal (56.3 %) manifestations. They also seemed to exhibit differences compared to other SLE patients: higher prevalence of fever, chronic cutaneous lupus erythematosus, oral and genital ulcers, neuropsychiatric manifestations, autoimmune cytopenia, and elevated biologic inflammatory markers. This review highlights the necessity of considering TNFAIP3 variants in SLE patients with early-onset disease, familial history, and/or specific clinical manifestations suggestive of autoinflammatory diseases. Recognizing HA20-SLE patients may improve our understanding of SLE pathogenesis and lead to better therapeutic strategies for these patients.

Expanding clinical characteristics and genotypic profiling of Yao syndrome in Chinese patients

Objectives

Yao syndrome (YAOS, OMIM# 617321) is a kind of systemic autoinflammatory diseases (SAIDs) linked to the nucleotide-binding oligomerization domain containing 2 (NOD2). Clinical reports of YAOS in China are sparse. Herein, we reported the largest YAOS cohort of Chinese patients to expand the understanding of its phenotype, genotype, and therapeutic responses.

Methods

This study enrolled 15 adult patients diagnosed with YAOS at Peking Union Medical College Hospital from April 2015 to May 2024. Whole-exome sequencing was performed on all patients. Clinical data, genetic variations, and treatment responses were documented and compared with a Caucasian cohort.

Results

The mean age of disease onset was 35 ± 17 years old. The most common clinical manifestations included recurrent high-grade fever (100%), gastrointestinal symptoms (73.3%), arthralgia/arthritis, fatigue, myalgia, and lower extremity swelling (46.7%). All patients exhibited elevated acute-phase reactants during episodes. 12 heterozygous NOD2 variants were identified, with Q902K in 4 patients, R471C in 3, and variants c.-14C>T, A110T, S127L, R311W, A432V, Y514H, R541P, A661P, K818Q, A886V each found in individual patients. 90% of the patients responded well to glucocorticoids, and 55.6% to sulfasalazine. 66.7% of patients who received TNF inhibitors achieved complete resolution of symptoms. Additionally, one patient each responded favorably to canakinumab and tocilizumab. Compared to the Caucasian cohort, our cohort exhibited a more balanced gender ratio and a higher proportion of recurrent fever, proteinuria/hematuria as well as more frequent leukocytosis, elevated acute phase reactants, and anemia. Lower proportions of arthralgia/arthritis, skin rashes, headaches, and sicca-like symptoms were noted in our cohort. Moreover, a higher proportion of patients in our cohort showed a good response to TNF inhibitors.

Conclusion

Chinese patients with YAOS had more pronounced inflammatory manifestations compared to the Caucasian cohort. Variants c.-14C>T, A110T, S127L, A661P, K818Q, A886V, R471C, and A432V were identified as novel NOD2 variants in YAOS. TNF, IL-6, and IL-1 inhibitors are the promising treatment options. These findings expand the clinical spectrum, genetic profile, and treatment efficacy of YAOS, underscoring the need for heightened awareness of this disease in diverse populations.

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.

[A20 haploinsufficiency: what do clinicians need to know?]

A20 Haploinsufficiency (HA20) is a monogenic autoinflammatory disease associated with an autosomal dominant mutation in the TNFAIP3 gene. It induces a defect in the inactivation of the pro-inflammatory NF-κB pathway. Less than 200 cases have been described worldwide. The clinical picture of the disease is essentially based on the association of recurrent fever and/or biologic inflammatory syndrome, aphtosis, often bipolar, and cutaneous folliculitis. However, the clinical spectrum of HA20 is very broad, including gastrointestinal (mainly colonic ulceration), articular, cutaneous, pericardial and lymph node involvement, as well as frequent association with organ-specific or non-specific autoimmune manifestations and/or autoantibodies, including antinuclear antibodies and anti-dsDNA. As a result, the diagnosis of a number of systemic or organic disorders, most notably Behçet's disease, Crohn's disease, and sometimes even systemic lupus, has been corrected to HA20 by molecular research for a heterozygous mutation with functional deficiency of TNFAIP3. Although the first signs of the disease often appear in the first years of life, the diagnosis is often made in adulthood and requires the involvement of both paediatric and adult physicians. Treatment for HA20 is not codified and relies on conventional or biological immunomodulators and immunosuppressants adapted to the patient's symptomatology. This review highlights the enormous diagnostic challenges in this autoinflammatory disease.

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.

A case of A20 haploinsufficiency complicated by autoimmune hepatitis

AIM

A20 haploinsufficiency (HA20) is a recently described autoinflammatory disease that manifests symptoms similar to those of Behçet's disease. However, little is known about the involvement of the liver in HA20. Here, we report a case of HA20 complicated by autoimmune hepatitis (AIH).

CASE PRESENTATION

A 33-year-old woman was previously diagnosed with HA20 and chronic thyroiditis, and was treated with prednisolone (PSL; 7.5 mg/day) and levothyroxine sodium hydrate (125 μg/day). She experienced general malaise and jaundice, and biochemical evaluation revealed elevated liver function with an aspartate aminotransferase level of 817 U/L, an alanine aminotransferase level of 833 U/L, and a total bilirubin of 8.3 mg/dL. Pathological evaluation of the liver biopsy revealed interface hepatitis and the patient was diagnosed with acute exacerbation of AIH. Upon increasing the PSL dose to 60 mg/day, the liver enzyme levels rapidly decreased. During tapering of PSL, azathioprine 50 mg/day was added, and there was no relapse of AIH with combination therapy of PSL 7 mg/day and azathioprine 50 mg/day.

CONCLUSION

This is the first report of biopsy-proven AIH in an Asian patient with HA20. This case has significant implications for the pathogenesis and treatment of AIH in patients with HA20.

A20 haploinsufficiency in a neonate caused by a large deletion on chromosome 6q

Haploinsufficiency of A20 (HA20) is a rare monogenic disease caused by heterozygous loss-of-function mutations in the tumor necrosis factor alpha-induced protein 3 (TNFAIP3) gene located on chromosome 6q23.3. The majority of disease-causing mutations in most cases of HA20 comprise single nucleotide variations, small insertions, or deletions in TNFAIP3, which result in a premature termination codon and subsequent disruption of its anti-inflammatory role. Large deletions have been reported sporadically. HA20 patients may present with a variety of autoinflammatory and autoimmune features during early childhood; however, cases with neonatal onset are rare. Here, we describe a Chinese neonate presenting with concomitant inflammatory and other syndromic manifestations caused by a 5.15 Mb interstitial deletion in chromosome 6; these deletions affect TNFAIP3. Taken together, the data extend the clinical and genetic spectra of HA20.

Haploinsufficiency of A20 caused by a novel pathogenic missense variant of TNFAIP3 and successfully treated with anti-TNF and immunosuppressive therapies

Loss-of-function of protein A20, encoded by TNFAIP3, leads to an early-onset haploinsufficiency of A20 (HA20). This study reports one Chinese child with HA20 and explores the genetic etiology of TNFAIP3 variant. The patient exhibited transient recurrent episodes of fever, intermittent signs of arthritis, gastrointestinal symptoms and multiple colonic ulcers. Laboratory tests revealed elevated inflammatory indicators and mild to moderate anemia. Genetic analysis identified a heterozygous de novo variant in his TNFAIP3 gene (c.740C＞T, p. P247L), which had never been reported before. The novel missense variation was validated to be pathogenic through causing insufficient expression of A20, over-activation of NF-κB signaling pathway and elevated levels of proinflammatory cytokines in response to stimulation by lipopolysaccharide. A combination of oral corticosteroids, TNF-α inhibitors and thalidomide freed him from symptoms and abnormal inflammatory indicators. Furthermore, continual improvement of the patient's condition was observed during a follow-up period of five months. We demonstrate a case with a de novo missense variant resulting in a loss-of-function of TNFAIP3, which expands the clinical spectrum of HA20. Cytokine antagonists and immunosuppressants may be effective drugs.

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.

Autoinflammatory manifestations in adult patients

Autoinflammatory diseases represent a family of immune-mediated conditions characterized by the unchecked activation of innate immunity. These conditions share common clinical features such as recurrent fever, inflammatory arthritis, and elevation of acute phase reactants, in the absence of an identified infectious etiology, generally without detectable serum autoantibodies, with variable response to glucocorticoids and in some cases colchicine, which represented the mainstay of treatment until cytokine blockade therapies became available. The first autoinflammatory diseases to be described were monogenic disorders caused by missense mutations in inflammasome components and were recognized predominantly during childhood or early adulthood. However, the progress of genetic analyses and a more detailed immunological phenotyping capacity led to the discovery a wide spectrum of diseases, often becoming manifest or being diagnosed in the adult population. The beneficial role of targeting hyperinflammation via interleukin 1 in complex non-immune-mediated diseases is a field of growing clinical interest. We provide an overview of the autoinflammatory diseases of interest to physicians treating adult patients and to analyze the contribution of hyperinflammation in non-immune-mediated diseases; the result is intended to provide a roadmap to orient scientists and clinicians in this broad area.