A number sign (#) is used with this entry because of evidence that familial Behcet-like autoinflammatory syndrome-1 (AIFBL1) is caused by heterozygous mutation in the TNFAIP3 gene (191163) on chromosome 6q23.

Familial Behcet-like autoinflammatory syndrome-1 (AIFBL1) is an autosomal dominant monogenic autoinflammatory disease characterized predominantly by painful and recurrent mucosal ulceration affecting the oral mucosa, gastrointestinal tract, and genital areas. The onset of symptoms is usually in the first decade, although later onset has been reported. Additional more variable features include skin rash, uveitis, and polyarthritis, consistent with a systemic hyperinflammatory state. Many patients have evidence of autoimmune disease. Rare patients may also have concurrent features of immunodeficiency, including recurrent infections with low numbers of certain white blood cells or impaired function of immune cells. The disorder results from a failure of mutant TNFAIP3 to suppress the activation of inflammatory cytokines in the NFKB (see 164011) signaling pathway; treatment with tumor necrosis factor (TNFA; 191160) inhibitors may be beneficial. Although some of the clinical features of AIFBL1 resemble those of Behcet disease (109650), the more common form of Behcet disease is believed to be polygenic, typically shows later onset in early adulthood, and has symptoms usually restricted to the mucosa (summary by Zhou et al., 2016; Aeschlimann et al., 2018, and Kadowaki et al., 2018).

Genetic Heterogeneity of AIFBL

See also AIFBL2 (301074), caused by mutation in the ELF4 gene (300775) on chromosome Xq26, and AIFBL3 (618287), caused by mutation in the RELA gene (164014) on chromosome 11q13.

Zhou et al. (2016) reported 14 patients, 12 females and 2 males, from 6 unrelated families with an autosomal dominant autoinflammatory disorder. The age at onset ranged from 2 to 16 years in all but 1 patient who had onset at age 29. Patients had oral and genital ulcers reminiscent of Behcet disease (see 109650). Additional features found in some patients included polyarthritis, skin rash, uveitis (3 patients), and inflammation or ulceration in the gastrointestinal tract (4 patients). Two patients had periodic fevers, 1 had hemolytic anemia, and 1 had idiopathic thrombocytopenia. Three patients from 1 family had lupus anticoagulant and other autoantibodies, and 3 additional unrelated patients had antinuclear autoantibodies. Some patients responded to treatment with TNF inhibitors or colchicine.

Aeschlimann et al. (2018) reviewed 15 patients from 6 unrelated families with AIFBL1 previously reported by Zhou et al. (2016) and reported an additional patient (P16) who developed mucosal and gastrointestinal ulcerations at 1 week of age and died at 8 years of age. His clinical features were consistent with both Crohn disease and Behcet disease. He had poor feeding with diarrhea and bowel perforation, small vessel central nervous system vasculitis, hyperglycemia, cataracts, and hypertension. Among the cohort of patients, the disease course was highly variable both between and within families, and some clinical features emerged over several years. All patients developed recurrent painful oral, genital, and/or gastrointestinal ulcers. Other common features that occurred at various time points during the disease included gastrointestinal complaints (56%), polyarthritis and/or arthralgia (56%), skin involvement (50%), and recurrent fever (50%). Ocular and cardiovascular involvement was also less frequently observed (19% of patients for each feature). Some patients had severe multisystemic inflammation, including 2 with CNS vasculitis. Laboratory studies usually showed elevation of acute phase reactants during relapses, as well as fluctuating levels of various autoantibodies. Seven patients (44%) had recurrent upper and lower respiratory tract infections, both bacterial and viral, and 2 sibs (P11 and P12 from family 5) had an immunodeficiency with low IgG, poor vaccination response, lymphopenia, and recurrent infections. None of the patients developed lymphoma or malignancy. The authors suggested that the phenotypic variability was due to modifying alleles or environmental factors.

Kadowaki et al. (2018) reported 30 patients from 9 unrelated Japanese families with AIFBL1. Twenty-two patients were confirmed to be TNFAIP3 mutation carriers, and 8 were clinically diagnosed with the disorder due to a Behcet-like phenotype with autosomal dominant inheritance. The patients, who ranged from 11 months to 71 years of age, mostly had onset of disease symptoms in the first decade, but a few had onset as teenagers. The main features included recurrent inflammatory attacks with fever and mucosal ulcerations resembling Behcet disease, although less than half of patients met the full diagnostic criteria for Behcet. Most patients had recurrent aphthous stomatitis, genital ulcers, or abdominal symptoms due to intestinal inflammation and ulceration. Polyarthritis was also occasionally observed; a few patients presented with polyarthritis before the onset of mucosal ulcers. The phenotype and severity of the disorder were heterogeneous, even within families. Some had only stomatitis, whereas others had more severe systemic involvement with onset in infancy. More variable features included skin rash, arthralgias, and pathergy. None had uveitis or ocular symptoms. There was a high frequency of autoimmune disorders, including systemic lupus erythematosus (SLE), psoriatic arthritis, juvenile idiopathic arthritis, autoimmune hepatitis, nephritic syndrome, and Hashimoto thyroiditis. Autoantibodies were identified in several patients. Laboratory studies showed an excess production of proinflammatory cytokines, including TNFA (191160), TNFR1 (191190), IL6 (147620), IL18 (600953), and IP10 (CXCL10; 147310), consistent with activation of the inflammasome. There was also an excess of differentiated T-helper 17 (Th17) cells. Treatment with anti-TNF agents successfully induced remission in some patients.

Dong et al. (2019) reported a 13-year-old Chinese boy who presented with a history of intermittent fever, diffuse lymphadenopathy, arthritis, and recurrent gastrointestinal ulcers. He also had skin rash and increased erythrocyte sedimentation rate (ESR). He had recurrent tonsillitis since 2 years of age and persistent EBV infection. Laboratory studies showed mild abnormalities in certain T-cell subsets, including increased proportion of effector memory cytotoxic T cells, and reduced numbers of T helper cells and CD8+ cytotoxic T cells. IgG was normal, but IgE and IgA were increased. Treatment with acyclovir and steroids resulted in transient clinical improvement. His mother, who also carried the mutation, had a milder disease course with onset of recurrent fevers and persistent oral ulcers since childhood. Both the patient and his mother had significantly increased levels of TNFA (191160) compared to controls, consistent with autoinflammation.

Gans et al. (2020) reported a 27-year-old man of Ashkenazi Jewish descent who was referred for recurrent fever, infection, mouth and genital ulcers, and chronic diarrhea since late childhood. He had a history of recurrent sinopulmonary infections, conjunctivitis, viral bronchitis, skin infection, dental caries, H. pylori gastritis, and EBV viremia. He also had hepatosplenomegaly. Laboratory studies showed hypogammaglobulinemia, poor vaccine response, low B and CD4+ T cells, decreased regulatory T cells, poor proliferative T-cell responses, and decreased numbers of NK cells that were not functional. These findings were consistent with a combined immunodeficiency in addition to a complex immune phenotype of autoimmunity and autoinflammation. His cytokine profile showed elevated inflammatory markers, and patient cells showed activation of the NFKB pathway with increased expression of interferon-response genes. Anemia was also noted. He responded well to anakinra treatment and immunoglobulin replacement. This case report expanded the immune dysregulation phenotype associated with TNFAIP3 mutations to include combined immunodeficiency.

The transmission pattern of AIFBL1 in the families reported by Zhou et al. (2016) and Kadowaki et al. (2018) was consistent with autosomal dominant inheritance with variable expressivity.

In affected members of 6 unrelated families with AIFBL1, Zhou et al. (2016) identified 6 different heterozygous truncating mutations in the TNFAIP3 gene (191163.0001-191163.0006). The mutations in the first 2 families were found by whole-exome sequencing and confirmed by Sanger sequencing; 3 subsequent mutations were found in 3 of 150 probands with a similar disorder who were directly screened for TNFAIP3 mutations. The sixth mutation was found in 1 of 768 individuals diagnosed with Behcet disease (109650) who underwent targeted sequencing. In vitro functional cellular expression studies showed that all mutations failed to suppress TNF-induced NFKB (see 164011) activity, although not in a dominant-negative fashion, which suggested haploinsufficiency as a disease mechanism. Patient cells showed reduced recruitment of TNFAIP3 to the TNFR complex (see 191190) compared to control cells. Patient-derived cells showed increased phosphorylation of IKKA (600664) and IKKB (603258) and subsequent degradation of I-kappa-B-alpha (NFKBIA; 164008), with nuclear translocation of the NFKB p65 subunit (RELA; 164014) together with increased expression of NFKB-mediated proinflammatory cytokines, consistent with activation of the NFKB pathway. Cells expressing the mutant proteins showed defective removal of lys63-linked ubiquitin from TRAF6 (602355), NEMO (IKBKG; 300248), and RIP1 (603453) after stimulation with TNF, indicating inefficient deubiquitination. Levels of proinflammatory cytokines were substantially higher in patient serum compared to controls, and showed evidence of increased IL1B (147720) signaling.

In 22 affected individuals from 9 unrelated Japanese families with AIFBL1, Kadowaki et al. (2018) identified heterozygous mutations in the TNFAIP3 gene (see, e.g., 191163.0007). There were 5 frameshift mutations, 2 splice site mutations, 1 nonsense mutation, and 1 missense variant, suggesting haploinsufficiency as the pathogenetic mechanism. Western blot analysis of cells carrying the mutations showed that the nonsense and frameshift mutations, but not the C243Y missense variant, caused decreased protein levels compared to controls. In vitro functional expression assays using a luciferase reporter showed that the nonsense and frameshift mutations, but not the C243Y missense variant, resulted in increased NFKB gene activity compared to wildtype, consistent with defective TNFAIP3 function. The authors postulated haploinsufficiency of A20 as the pathogenetic disease mechanism.

In a 13-year-old Chinese boy with AIFBL1, Dong et al. (2019) identified a heterozygous missense mutation in the TNFAIP3 gene (M476I; 191163.0008). The mutation, which was found by trio-based exome sequencing and confirmed by Sanger sequencing, was not present in public databases. The mutation was inherited from the patient's mother who had milder symptoms, consistent with variable penetrance and expressivity. Patient cells showed decreased TNFAIP3 mRNA and protein levels after stimulation with LPS compared to controls. Patient cells also showed increased activation of the NFKB1 (164011) signaling pathway compared to controls, even without stimulation.

In a 27-year-old man of Ashkenazi Jewish descent with AIFBL1, Gans et al. (2020) identified a heterozygous frameshift mutation in the TNFAIP3 gene (191163.0009). The mutation, which was found by whole-exome sequencing, was not present in population databases. The mutation occurred in the N-terminal ovarian tumor domain. Familial segregation studies and functional studies of the variant were not performed, but it was predicted to result in haploinsufficiency of TNFAIP3.