Abstract: FR-PO448
An Unexpected Cause of Hypokalemia
Session Information
- Pediatric Nephrology - I
November 04, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
Abstract Time: 10:00 AM - 12:00 PM
Category: Genetic Diseases of the Kidneys
- 1102 Genetic Diseases of the Kidneys: Non-Cystic
Authors
- Schretlen, Claire Frances, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Haq, Kanza, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Cervantes, Carmen Elena, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
- Hanouneh, Mohamad A., Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
Introduction
Gitelman syndrome is an autosomal recessive hypokalemic and salt wasting tubulopathy caused by loss-of-function mutations in the sodium chloride cotransporter encoded by SLC12A3, leading to disrupted entry of sodium and chloride at the apical membrane of distal convoluted tubule cells (fig 1).
Case Description
A 20-year-old man with bulimia nervosa and CKD stage IIIA was referred to clinic for refractory hypokalemia attributed to vomiting. Home medications included potassium chloride 60 mEq four times daily. His blood pressure was 100/60 mmHg. Basic laboratory values are shown in fig 2A. Further workup revealed elevated serum renin (62.6 ng/L) and normal serum aldosterone (10 ng/dL). Urine studies showed random urine chloride of 60 mEq/L with renal losses of sodium, potassium, and magnesium along with hypocalciuria (fig 2B). Genetic testing confirmed the diagnosis of Gitelman syndrome with 2 pathogenic variants in the SLC12A3 gene [c.2221G>A (p.G741R) and c.247C>T (p.R83W)]. Aldosterone secretion is independently regulated by angiotensin II and plasma potassium concentrations. As such, aldosterone may not increase despite of high renin/angiotensin II levels in the context of severe hypokalemia. This can explain the normal level in our case. Further, the patient’s CKD is likely due to longstanding severe hypokalemia causing tubulointerstitial disease. He was started on amiloride 10 mg daily with a normalization of potassium and magnesium levels without supplementation.
Discussion
Gitelman syndrome is associated with reduction of extracellular fluid volume, hyperreninemia and secondary hyperaldosteronism, metabolic alkalosis, renal wasting of potassium, sodium, and magnesium, and decreased urinary excretion of calcium. Its diagnosis is confirmed with genetic testing.