Low copy numbers of three variants in the α-defensin gene locus (DEFA1A3) are associated with an increased risk of IgA nephropathy (IgAN) as well as with renal dysfunction and increased serum levels of IgA1 and galactose-deficient IgA1 in patients with this disease, say researchers. Ai et al. identified these variants in two independent southern Han Chinese cohorts and confirmed their findings in a Caucasian cohort. They report that copy number variation in the DEFA1A3 locus explains 4.96% of disease risk in patients with IgAN, so might be a potential target for therapy.