Initial Suspicion of Autosomal Dominant Polycystic Kidney Disease Resulted in a Diagnosis of Autosomal Dominant Tubulointerstitial Kidney Disease Caused by a UMOD Mutation.

A 44-year-old woman presented with bilateral kidney cysts, scattered hepatic cysts, and a family history of polycystic kidney disease initially suspected of being autosomal dominant polycystic kidney disease (ADPKD). However, her clinical course showed atypical features: a modest total kidney volume increase (436 to 643 mL over 4 years) and rapid progression to end-stage kidney disease by 48 years old. Genetic testing revealed autosomal dominant tubulointerstitial kidney disease caused by a UMOD mutation (ADTKD-UMOD). This case highlights the importance of considering genetic testing in ADPKD cases with atypical features, since the diagnosis affects treatment decisions, including kidney replacement therapy selection.