Large Kidney Cysts in HNF1B Nephropathy Mimicking Autosomal Dominant Polycystic Kidney Disease

Rationale: Hepatocyte nuclear factor 1 beta (HNF1B) nephropathy is a rare autosomal dominant monogenic kidney disease. We present a case mimicking autosomal dominant polycystic kidney disease (ADPKD), highlighting the phenotypic heterogeneity of HNF1B-related disease. Presenting concerns of the patient: A 37-year-old man presented with hypertensive urgency, accompanied by flank pain and abdominal distension. Despite the absence of familial kidney disease, imaging revealed large bilateral kidney cysts resembling ADPKD. Diagnosis: We initially suspected de novo ADPKD. However, negative genetic testing results for PKD1 and PKD2 led to a 43-gene cystic kidney sequencing panel which identified a deletion encompassing the entire HNF1B gene. Intervention: To alleviate discomfort caused by the kidney cysts, ultrasound-guided aspiration and foam sclerotherapy were performed. Tolvaptan, used for treating high-risk ADPKD, was not prescribed after confirming the diagnosis was HNF1B nephropathy. Outcomes: A diagnosis of HNF1B nephropathy was reached following gene panel testing. Abdominal symptoms improved following cyst aspiration and foam sclerotherapy. Novel findings: HNF1B nephropathy has a variable presentation but can lead to cysts appearing like ADPKD. A 43-gene cystic kidney sequencing panel identified the diagnosis in this uncertain case.