C3 and autoimmune polyendocrinopathy: Among the whole group of 131 patients at diagnosis, 80.2% had raised anti-dsDNA antibodies and 67.2% low C3 levels; 55.7% of patients had positive anti-Ro, 52.7% anti-RNP, 36.6% anti-Smith and 21.4% anti-La antibodies; 43.5% of patients had at least one overlapping disease, the most frequent being Sjögren’s syndrome (n = 17, 13%), APS (n = 16, 12.2%), RA (n = 11, 8.4%) and hypothyroidism (n = 13, 9.9%).