Circulating BAFF levels are elevated in patients with systemic lupus erythematosus (SLE; Zhang et al., 2001; McCarthy et al., 2013; Salazar-Camarena et al., 2016), multiple sclerosis (MS; Kannel et al., 2015; Steri et al., 2017), rheumatoid arthritis (Cheema et al., 2001), or IgA nephropathy (Xin et al., 2013; Li et al., 2014). The gene discussed is TNFSF13B; the disease is systemic lupus erythematosus.