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

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.

L’haploinsuffisance de A20 : que doit connaître le clinicien?

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.

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.

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.