The study looked at how often familial IgA nephropathy is associated with other genetic kidney diseases. The researchers analyzed eleven families with biopsy-confirmed IgA nephropathy and compared them with 39 people with the sporadic form of the disease. They found that at least five (45%) and possibly as many as nine (82%) of the eleven families studied had heterozygous genetic variants associated with other kidney diseases, such as Alport syndrome, ADTKD-HNF1B, and focal segmental glomerulosclerosis. In contrast, only two of 39 people with sporadic IgA nephropathy (5%) had variants causing another genetic kidney disease. Interestingly, sometimes a proband with IgA nephropathy did not have a genetic variant that was present in other affected family members, or a combination of variants corresponding to two different diseases was present in the family. The study recommends offering genetic testing to individuals from families with IgA nephropathy, as coexisting genetic kidney diseases may explain many cases of familial nephropathy.