For example, for adult-onset polycystic kidney disease, which is typically an AD trait, homozygosity of hypomorphic variants in the polycystic kidney disease 1 gene PKD1 may be disease causing, while heterozygous mutations lead to a mild phenotype with only minor renal cysts, altogether rather advocating for incomplete penetrance than for true AR inheritance (32). The gene discussed is PKD1; the disease is kidney disorder.