In addition, in humans, ADPKD is a heterozygous state, whereby mutations leading to loss of one PKD1 or PKD2 allele is combined with somatic mutations in the kidney (i.e., a second hit) to cause renal cystic disease [20], [21], [22], [23], [24]. The gene discussed is PKD2; the disease is autosomal dominant polycystic kidney disease.