In 2012, new classification criteria of SLE were published by the SLICC group (Systemic Lupus International Collaborating Clinics) (3), and expert consensus included low complement protein 3 and 4 (C3 and C4) or low CH50 [complement hemolytic activity (4)] in the classification criteria. The gene discussed is C4A; the disease is systemic lupus erythematosus.