Purpose Mutations in TNFAIP3 have recently been recognized as critical cause leading to early-onset autoinflammatory and autoimmune syndrome. And gradually more TNFAIP3 gene mutations were reported, most were frameshift and truncation mutations, and only a few were missense mutations. Here, we reported five Chinese patients manifested with unclassified autoinflammatory syndrome which exhibit two identical novel missense heterozygous variants of uncertain significance (VUS) mutations in TNFAIP3 and verified their pathogenicity. Methods We analyzed the clinical, genetic, and immunological features of five Chinese patients with two novel missense heterozygous VUS in TNFAIP3, and verified their pathogenicity. Results We identified two missense heterozygous mutations ( c.208 G>A, p.Asp70Asn and c.770 T>C, p.Phe257Ser), which were located in the highly conserved residue of amino-terminal ovarian tumor (OTU) domain of TNFAIP3. Only the p.Asp70Asn mutation changes the structure of TNFAIP3 but both variants alter the expression of A20 in peripheral blood mononuclear cells (PBMCs). Accordingly, in vitro TNF-α stimulated patients’ PBMCs showed higher levels of p65 NF-kB phosphorylation and increased IkBα degradation, as well as increased production of the proinflammatory cytokines IL-1β, IL-18 and TNF-a after lipopolysaccharide (LPS) stimulation in vitro Conclusion our data further expands the understanding of the HA20 disease.andhighlights the necessity of functional analysis to evaluate the pathogenicity of VUS in TNFAIP3 for accurate diagnose of HA20.