The diagnosis of autosomal dominant polycystic kidney disease (ADPKD) relies on imaging criteria in the setting of a positive familial history. Molecular analysis, seldom used in clinical practice, identifies a causative mutation in >90% of cases in the genes PKD1, PKD2, or rarely GANAB. We report the clinical and genetic dissection of a 7-generation pedigree, resulting in the diagnosis of 2 different cystic disorders. Using targeted next-generation sequencing of 65 candidate genes in a patient with an ADPKD-like phenotype who lacked the familial PKD2 mutation, we identified a COL4A1 mutation (p.Gln247*) and made the diagnosis of HANAC (hereditary angiopathy with nephropathy, aneurysms, and muscle cramps) syndrome.