An Unusual Cause of Hypokalemia to Consider

Abstract

Apparent mineralocorticoid excess syndrome is a rare disorder that can be acquired through inhibition of the enzyme 11 β-hydroxysteroid dehydrogenase type 2 by various substances such as bile acids. We report the case of a 61-year-old woman presenting with painless jaundice. Computed tomography demonstrated a pulmonary as well as a pancreatic tumor, with multiple metastases and dilated bile ducts. Laboratory findings showed persistent hypokalemia despite aggressive enteral and parenteral supplementation, as well as hypertension, metabolic alkalosis, and elevated cholestasis enzymes. Urinary potassium excretion was inappropriately high. Plasma aldosterone concentration was 0.97 ng/dL (26.91 pmol/L) (reference range, 2.21-25.30 ng/dL [61.31-701.82 pmol/L]) and direct renin concentration was 3.9 mIU/L (2.1 ng/L) (reference range, 4.4-46.1 mIU/L [2.53-27.42 ng/L]). Endogenous hypercortisolism was ruled out. After the placement of a metal biliary stent via endoscopic retrograde cholangiopancreatography and the subsequent decrease in cholestasis enzyme levels, potassium levels, hypertension, and metabolic alkalosis gradually normalized. The case was ultimately diagnosed as apparent mineralocorticoid excess syndrome resulting from 11 β-hydroxysteroid dehydrogenase type 2 inhibition caused by elevated bile acids secondary to malignant obstruction of the biliary tract.

Keywords: HSD11B2; apparent mineralocorticoid excess syndrome; bile acids; glycyrrhetinic acid-like factors; hypokalemia; pseudohyperaldosteronism.

Figure 1.

Evolution of potassium level and supplementation. Evolution of kalemia (mmol/L; mEq/L) and potassium supplementation (mmol/day) throughout the patient's hospitalization. On the 10^th day of admission, the patient presented the lowest kalemia value: 2.4 mmol/L (mEq/L) despite receiving 153 mmol/day of potassium. On the 7^th day of admission, an endoscopic retrograde cholangiopancreatography (ERCP) with sphincterotomy and placement of a metallic biliary stent was performed. As a result of this procedure, cholestatic enzyme levels and the associated hypokalemia gradually normalized, which allowed for a reduction in potassium supplementation.

Figure 2.

Evolution of total bilirubin level. Evolution of total bilirubin level (A, mg/dL); (B, mmol/L) throughout the patient's hospitalization. On the 7^th day of admission, an endoscopic retrograde cholangiopancreatography (ERCP) with sphincterotomy and placement of a metallic biliary stent was performed. As a result of this procedure, cholestatic enzyme levels and the associated hypokalemia gradually normalized, which allowed for a reduction in potassium supplementation.