UNASSIGNED: A 3-year-and-6-month-old child was reported to have recurrent high fever with generalized lymph node enlargement and significant elevation of inflammatory markers such as C-reactive protein and procalcitonin in tests. Later, whole exome sequencing determined that the child\'s disease was haploinsufficiency of A20 (HA20).
UNASSIGNED: After immunosuppressive therapy, the child\'s symptoms improved significantly, and the inflammatory markers dropped to the normal range.
UNASSIGNED: Because of the characteristics of HA20, this disease is often underdiagnosed and misdiagnosed in clinical practice. By reporting this case of HA20 in a child, we hope to increase the awareness of this disease in the clinic.

UNASSIGNED: Haploinsufficiency of A20 (HA20) is a newly described rare autoinflammatory disease caused by TNFAIP3 gene mutations. HA20 has seldom been documented in the Chinese population. Herein, we report eight patients with HA20 from three unrelated families in China.
UNASSIGNED: Eight Chinese Han patients were diagnosed with HA20 in our department from 2018 to 2021. Their clinical data and genotypes were carefully documented and studied. The newly identified variants were functionally verified. We also conducted a systematic literature review of HA20, and the clinical characteristics and genotype of HA20 between the Chinese population and other populations were compared.
UNASSIGNED: Eight HA20 patients from three families comprised six adults and two children. There was one man and seven women. The clinical characteristics included recurrent oral ulcers (8/8, 100%), fever (4/8, 50%), perianal ulcer (3/8, 38%), skin lesions (2/8, 25%), arthritis (1/8, 13%), and uveitis (1/8, 13%). Three TNFAIP3 variants, A547T, c.1906+2T>G, and R271X, were identified. Two novel variants, A547T and c.1906+2T>G, were validated to be pathogenic in our study. In a literature review a total of 126 patients with HA20 reported by 35 articles were included. The clinical phenotype of Chinese HA20 patients was similar to that of patients from other populations except for a lower frequency of genital ulcers (16.7% vs. 54.4%, p < 0.01). Autoantibodies were detectable in approximately one-third of the 126 patients, among which ANA and anti-thyroid antibodies were commonly seen.
UNASSIGNED: The rarity and diversity of phenotypes make the diagnosis of HA20 a huge challenge to physicians. HA20 should be considered in child-onset patients with manifestations that resemble Behçet\'s syndrome, especially those whose family members have similar symptoms. Gene testing is critically helpful for the diagnosis of HA20. Two novel TNFAIP3 variants, A547T and c.1906+2T>G, were identified in this study.

A20, encoded by TNFAIP3, is an effective anti-inflammatory molecule that plays a crucial role in inhibiting NF-κB signal transmission and is linked to multiple inflammatory diseases. It has been reported that the haploinsufficiency of A20 (HA20) caused by multiple base mutations in TNFAIP3 shows early-onset spontaneous Behçet-like disease. However, the mechanisms by which A20 mutations involved in inflammatory disease are incompletely defined. Herein, we reported a novel TNFAIP3 (c.1804A > T, p.T602S) variation, which has not been reported before. Summarizing the patient\'s immunodeficiency phenotype, we aimed to delineate the underlying mechanism for regulation of inflammation and immunity. Candidate genes associated with the Behçet-like phenotypes of the patient were screened and identified by using whole-exome and sanger sequencing. Functional studies were performed in A20(c.1804A > T, p.T602S) patient-derived peripheral blood mononuclear cells (PBMCs) and THP-1 cell lines by lentivirus mediating stable over-expression of A20 and A20(c.1804A > T, p.T602S) to analyze the activity of NF-κB signaling pathway. The clinical manifestations in patients with syndrome are Behçet-like disorder, and sequencing revealed heterozygous mutation in TNFAIP3 (c.1804A > T, p.T602S). Functional tests found that the PBMCs of the patient and his family carrying this heterozygous variant stimulated by LPS, TNF-α, or IL-1β, increased the levels of inflammatory factors and induced over-activation of the canonical NF-κB signaling pathway. Similar results were also observed in the stable transduction THP-1 (A20, c.1804A＞T) cell line stimulated by LPS, TNF-α or IL-1β. The novel loss-of-function A20 variation (c.1804A > T, p.T602S) causes over-activation of the canonical NF-κB signaling pathway and fail to terminate NF-κB signaling in response to stimulation by inflammatory cytokines. The variation triggers a dominantly-inherited Behçet-like disorder caused by haploinsufficiency of the A20 protein. Identification of the novel A20 mutation attaches great importance to prenatal diagnosis and fetal therapeutic intervention, drastically reducing the risk of newborns suffering from HA20.

Objective: Intestinal Behcet\'s disease (iBD) is an autoimmune disorder diagnosed by typical intestinal ulcers and systemic Behcet\'s disease (BD) manifestations. Haploinsufficiency of A20 (HA20) is a recently described autoinflammatory disease with a phenotype resembling BD, caused by heterozygous loss-of-function mutations in TNFAIP3 gene (encoding A20). Methods: We described a 29-year-old female with iBD-like symptoms including relapsing ulceration of intestinal anastomosis, recurrent oral ulcers and vasculitis in extremities. Due to the atypical intestinal ulcers with long segmental involvement and intestinal obstruction, whole exome sequencing (WES) was performed to screen for the underlying genetic defect and the identified gene was confirmed by Sanger sequencing. The expression levels of A20 was evaluated by Western blot. Sanger sequencing and Western blot were also performed in the patient\'s family members. Results: A heterozygous mutation of TNFAIP3 (c.305A>G, p. Asn 102 Ser) was identified in the patient. The identical TNFAIP3 mutation was also found in her father and brother who had suffered from recurrent oral ulcers since childhood. Functional experiments revealed that the expression of A20 was decreased in the peripheral blood mononuclear cells of the patient and her family members who carried the TNFAIP3 mutation. Conclusion: We described a Chinese patient with a novel heterozygous mutation in TNFAIP3 who developed iBD-like symptoms. We proposed that the TNFAIP3 heterozygous mutation (c.305A>G, p. Asn 102 Ser) with an insufficient expression of A20 may be associated with the iBD phenotype in patients.