TNFSF13B and systemic lupus erythematosus: Systemic lupus erythematosus (SLE) is an unpredictable and multifaceted chronic systemic autoimmune disease.1 One of the most prominent breakthroughs in SLE has been the discovery of the pathogenic role of B cell‐activating factor from the tumor necrosis factor (TNF) family (BAFF) [also known as B lymphocyte stimulator (BLyS)].2 BAFF has a crucial role in B cell maturation, differentiation and survival, and is part of the BAFF/a proliferation‐inducing ligand (APRIL) system.