Abstract: SA-PO0614
Hypomagnesemia as the Initial Manifestation of HNF1B Whole-Gene Deletion
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Case Reports - 2
October 24, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Dhayalan, Dhayanithi, Adventist Health Central Valley Network, Hanford, California, United States
- Adapa, Sreedhar R., Adventist Health Central Valley Network, Hanford, California, United States
- Rajendran, Abinaya, Pondicherry Institute of Medical Sciences, Puducherry, PY, India
Introduction
HNF1B-related disease is a recognized cause of renal magnesium wasting and may initially present with hypomagnesemia before the development of diabetes, chronic kidney disease, or other structural abnormalities. Early diagnosis is important because affected patients require longitudinal surveillance for renal and extrarenal manifestations
Case Description
A 22-year-old woman with migraine, asthma, and reactive airway disease was referred for evaluation of chronic refractory hypomagnesemia. Her course was complicated by recurrent syncopal episodes suspected to be secondary to QTc prolongation from severe hypomagnesemia. Review of systems was notable only for chronic malformed stools with liquid consistency occurring 3 to 4 times daily. She denied alcohol use, gastrointestinal surgery, daily proton pump inhibitor use, prolonged antibiotic exposure, diabetes, diuretic use, nephrolithiasis, urinary symptoms, and family history of kidney or electrolyte disorders. Vital signs and physical examination were unremarkable. Complete blood count and metabolic panel were normal except for severe hypomagnesemia, with serum magnesium intermittently falling below 1.0 mg/dL despite aggressive oral replacement. Parathyroid hormone was 31 pg/mL and calcium was 10.2 mg/dL. Twenty-four-hour urine studies demonstrated magnesium excretion of 147 mg, consistent with renal magnesium wasting. Kidney ultrasound showed bilateral simple renal cysts. Genetic testing with copy-number analysis identified an HNF1B whole-gene deletion. She remained refractory to magnesium oxide 800 mg four times daily and amiloride 5 mg daily, and was transitioned to magnesium glycinate, with intravenous magnesium under consideration.
Discussion
Young patients with unexplained hypomagnesemia should be considered for early genetic evaluation, particularly when urinary magnesium wasting is demonstrated. HNF1B mutations are associated with hypomagnesemia, renal cysts, MODY, hyperuricemia, and parathyroid abnormalities, and early recognition can clarify the etiology, guide management, and enable long-term surveillance for associated renal and extrarenal complications