We confirmed the association of HLA-DR3-DQ2 positive T1D with other autoimmune diseases and discovered credible candidate loci for clustering of AIDs: RGS1 and possibly NRP1, FUT2, and CD69 are risk loci for having other AIDs in addition to T1D, and within the region between CCR3 and CCR5 might exist a risk locus for clustering of AIDs in families of patients affected by T1D. This evidence concerns the gene FUT2 and autoimmune disease.