A 50% dosage reduction of gene product, known as haploinsufficiency, as found in
heterozygotes with an inactivating mutation, is not usually associated with a detectable
physiologic effect. Consequently, either loci associated with dominant disease are those
rare ones that are sensitive to haploinsufficiency, or an additional mechanism plays a role to
enhance the effect of the single mutant allele. In the case of autosomal dominant polycystic
kidney disease (ADPKD), adult-onset disease is characterized by focal cyst development …