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Kidney Week

Abstract: FR-PO608

SLC5A2 Mutation in a Patient Presenting with Volume Depletion

Session Information

Category: Genetic Diseases of the Kidneys

  • 1202 Genetic Diseases of the Kidneys: Non-Cystic

Authors

  • Martinez Lopez, Maria Fernanda, Universidad Iberoamericana, Santo Domingo, Dominican Republic
  • Janosevic, Danielle, Indiana University School of Medicine, Indianapolis, Indiana, United States
Introduction

We present a patient found to have a heterozygous SLC5A2 mutation in the absence of glucosuria with volume depletion and underlying tubulopathy.

Case Description

30 year old African American male, no prior medical history with chief complaint of fatigue and persistent alkalemia on bloodwork. Evaluation of fatigue included a sleep study negative for central/obstructive sleep apnea, pulmonary function testing without obstruction/restriction. He stated the fatigue had been worsening over the past year, prior asymptomatic, water intake 4L/day. He denied the use of laxatives, diuretics, antacids, herbals and medications. ROS was positive for orthostasis, palpitations, denied: poor oral intake, nausea, vomiting, diarrhea, polyuria. Family history unknown, and he never had surgery. Exam revealed BP: 89/60 mmHg, HR 88 bpm, RR 16 bpm, small/thin stature, positive orthostatics, moist mucous membranes. Labs remarkable for Serum: bicarbonate 34 mmol/L, normal: sodium, potassium, chloride, magnesium, phosphorus, creatinine, glucose, elevated plasma renin 58.9 pg/ml. Fractional excretions of: Sodium 0.3%, Chloride 0.5% Magnesium 5%, Potassium 17%, and urine significant for K/Cr 9 and Ca/Cr 0.05, no glucosuria on urinalysis, diuretic screen negative, Uosm 685 mOsmol/kg. Renal US: 1 simple cyst, absence of nephrocalcinosis. Differential included volume depletion on background of salt wasting tubulopathy. Genetic testing performed which revealed SLC5A2 heterozygous mutation (c.1024G>T, p.Glu342*). He was counseled to intake copious fluids and sodium chloride to mitigate the effects of volume depletion and symptoms improved.

Discussion

SLC5A2 encodes the renal sodium/glucose transporter, responsible for renal glucose reabsorption. While homozygous mutations result in glucosuria which may lead to volume depletion, heterozygous mutations are variable with differing phenotypes, and many do not manifest with overt volume depletion in the absence of glucosuria. Here we present a patient with a heterozygous mutation in the SLC5A2 gene without glucosuria, who presented with evidence of volume depletion and electrolyte wasting tubulopathy. This case emphasizes the need for phenotyping various mutations in the SLC5A2 gene, to aid in the differential of metabolic alkalosis and altered tubular handling of electrolytes in the setting of such mutations.