Patient 2, the 29-year-old brother of Patient 1, shares the same HNF1B defect, presenting with left kidney agenesis and multiple right kidney cysts contributing to renal function deterioration (latest eGFR 79 mL/min/1.73 m2, eGFR decline at 3 mL/min/1.73 m2/year), dorsal pancreas agenesis, psoriasis, diabetes and abnormal liver function tests. Here, HNF1B is linked to diabetes mellitus.