Tolvaptan, used for treating high-risk ADPKD, was not prescribed after confirming the diagnosis was <i>HNF1B</i> nephropathy.<h4>Outcomes</h4>A diagnosis of <i>HNF1B</i> nephropathy was reached following gene panel testing. The gene discussed is HNF1B; the disease is autosomal dominant polycystic kidney disease.