The higher frequency of these ABCB6 variants in these severely affected porphyria patients of European descent compared with European Americans tabulated in the NHLBI Exome Variant Server (22.2% versus 3.8%, Fisher's exact test, P=0.0034, two sided; http://evs.gs.washington.edu/EVS/; Supplementary Table 4) suggests these variants might be non-functional. The gene discussed is ABCB6; the disease is porphyria.