Abstract Background and Aims Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a systemic renal ciliopathy characterized by progressive renal cyst expansion and extrarenal manifestations following loss-of-function mutations. ADPKD is primarily caused by PKD1 (72-75%) and PKD2 (15-18%), with a high level of allelic heterogeneity: it is rare to identify the same germ-line mutation in different families since mutations are “private”. In recent years the identification of several new genes has underlined the genetic heterogeneity of ADPKD. The Aim of this study is to describe a cohort of PKD2 gene-linked families with the same germ-line mutation. Method Patients (pts) with ADPKD referral to the Genetic Kidney Diseases clinic of the UOC of Nephrology of ULSS8 Berica (San Bortolo Hospital in Vicenza) were enrolled and followed prospectively. Diagnosis of ADPKD was made upon the revised Ravine's criteria. Complete clinical details were recorded, including family history and pedigree. We performed NGS with Sophia Genetic “Nephropathies Solution” Panel or Sanger sequencing to identify disease-causing mutations in the cohort. Furthermore, microsatellite analysis was performed in PKD2 gene pts with same germ-line nonsense mutation c.2533C>T (p.Arg845Ter), to identify disease haplotype. Results We identified a cohort of 30 ADPKD pts belonging to 13 families with same PKD2 germ-line nonsense mutation c.2533C>T (p.Arg845Ter). Regarding pedigree analysis, 8 families had their origin from the same geographical area and the remaining 5 were from an area 100 km away. In 4 families, we found a common individual. Concerning the microsatellite analysis, all 30 pts shared the same haplotype Chromosome 4 CEN – VG2 (TG)20, VG3 (TA + GA)32, VG4 (CA)13, D4S2929 (AC)26, D4S1563 (TG)20 – TEL indicating that those families may originate from a common ancestor. Conclusion We found the same PKD2 germline mutation in 30 ADPKD pts belonging to 13 families that share the same haplotype. Since, ADPKD mutations are “private” and Vicenza province counts almost 860000 inhabitants, our findings provide an evidence that a founder effect exists, maybe due to a founder effect in our region.