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Abstract: SA-PO701

Diagnostic Dilemma of a Case of Complex Refractory Hypomagnesemia

Session Information

Category: Fluid, Electrolytes, and Acid-Base Disorders

  • 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical

Authors

  • Elhilali, Osama, University of Florida College of Medicine - Jacksonville, Jacksonville, Florida, United States
  • Hasan, Irtiza, University of Florida College of Medicine - Jacksonville, Jacksonville, Florida, United States
  • Heilig, Charles W., University of Florida College of Medicine - Jacksonville, Jacksonville, Florida, United States
Introduction

Magnesium (Mg+) diisorders are usually less common & not well investigated. Renal Mg+ wasting can be associated with Barter syndrome, Gitelman syndrome, Familial renal magnesium wasting, Hepatocyte nuclear factor-1-beta gene mutations, Epidermal growth factor gene mutation, or Cyclin M2 mutations.

Case Description

A 69-year-old white female with PMH of CKD Stage 2, HTN, DM, Sarcoidosis, presented with severe chronic hypomagnesemia. Her daughter also has chronic hypomagnesemia. She was on pantoprazole & HCTZ for >7 years, HCTZ was discontinued 1 year prior to the presentation. Now on oral & Mg+ IV infusion (4 gm/month). Other medications included Spironolactone, Gabapentin, Glyburide, Lantus, Aspirin, and Mepolizumab. Pantoprazole was discontinued, continued on oral Mg+, but increased Mg+ IV infusions (4 gm/week). Despite these changes her Mg+ level was still ranging between 0.9 to 1.3 mg/dL. Later stopping spironolactone was also unsuccessful to improve the Mg+ level, but her K+ dropped to low normal. Workup as follows: Na+ 140 mmol/L, K+ 3.4 mmol/L, Cl- 102 mmol/L, CO2 27 mmol/L, BUN 8 mg/dL, Creatinine 0.7 mg/dL, Glucose 205 mg/dL, Ca+ 9.7 mg/dL, Phosp 4.2 mg/dL & Mg+ ranging between 1.0 to 1.3. UA- normal. 24-hour urine lytes: Mg+ 59.4 mg, Ca+ 68 mg/dL, K+ 50 mmol, Na+ 90 mmol. 24-hour Creatinine 0.8 g. Urine Mg+ 4.4 mg/dL. Fractional excretion (FE) of Mg+ 6.87%.

Discussion

A daily excretion of >10 to 30 mg or a FE of Mg+ above 3 to 4% in a person with hypomagnesemia & normal kidney function, indicates renal Mg+ wasting. In contrast, a 24-hour urinary Mg+ excretion of <10 mg or a FE of Mg+ <2% usually indicates an extrarenal Mg+ losses (typically GI). Our patient’s FE of Mg+ is 6.87%, & 24-hour urine Mg+ was 59.4 mg. Gitelman syndrome (GS) is the most common form of familial renal Mg+ wasting. Bartter syndrome (type 3) that resemble GS, may also present with hypomagnesemia. The 24-hour urine calcium/creatinine ratio is 85 mg/g. The upper range for the urine calcium/creatinine ratio in adults is about 200 mg/g. The lower limit of normal for calcium excretion is unknown. A spot urine calcium/creatinine ratio of <70 mg/g has been proposed to define hypocalciuria in adults when Gitelman syndrome is suspected. Our patient has a spot ratio of 19 mg/g. The patient is undergoing genetic testing to identify the etiology of hypomagnesemia.