At least two probands had monogenic disease and one third carried novel or rare variants in genes well accepted to cause monogenic SLE: ACP5, C3, C4A, C4B, DNASE1, IFIH1, NRAS, RNASEH2B, RNASEH2C and SAMHD1. The gene discussed is RNASEH2C; the disease is systemic lupus erythematosus.