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.