Although it is difficult to define HLA-DRB1*1501 as a molecular biomarker of anti-GBM nephritis or lupus, the fact that these identical twins were both HLA-DRB1*1501 homozygotes supports the possible association of this allele with anti-GBM and lupus. Here, HLA-DRB1 is linked to systemic lupus erythematosus.