Laboratory examination showed hyperkalemia (serum potassium of 5.3 mmol/L [normal 3.6–4.8]), normal serum sodium (139 mmol/L, normal 135–145), hyperchloremia (107 mmol/L, normal 95–105), hypomagnesemia at 0.55 mmol/L (normal 0.73–1.00), elevated serum creatinine at 1.18 mg/dL (normal <0.90) with an estimated glomerular filtration rate of 51 mL/min (CKD-EPI [40], normal 90–140), elevated urea of 47 mg/dL (normal 21–43), suppressed renin concentration (<1.0 pg/mL [normal 1.7–23.9]), and aldosterone of 157 pg/mL (normal 12–236). Here, REN is linked to familial primary hypomagnesemia.