Familial Renal Glycosuria Presenting with Longstanding Asymptomatic Glycosuria and New-Onset Ketonuria and Bilirubinuria: A Case Report

A Case Report

Abstract

INTRODUCTION

Glycosuria, defined as the presence of glucose in the urine, is most commonly associated with hyperglycemia resulting from diabetes mellitus or other metabolic disorders. Under normal physiological conditions, filtered glucose is almost completely reabsorbed in the proximal renal tubules through sodium-glucose cotransporters, resulting in negligible urinary glucose excretion. Therefore, persistent glycosuria in the presence of normal blood glucose levels is an uncommon finding that warrants further clinical evaluation to identify underlying renal causes [1,2]. Familial renal glycosuria (FRG) is a rare inherited renal tubular disorder characterized by persistent urinary glucose excretion despite normal plasma glucose concentrations and preserved renal function. The condition is most commonly caused by mutations in the SLC5A2 gene, which encodes the sodium-glucose cotransporter-2 (SGLT2) responsible for the majority of renal glucose reabsorption in the proximal tubule [3,4]. Impaired SGLT2 function results in isolated glycosuria without the systemic manifestations typically observed in diabetes mellitus. FRG is generally considered a benign condition and is frequently detected incidentally during routine laboratory investigations [5].The differential diagnosis of isolated glycosuria includes diabetes mellitus, Fanconi syndrome, renal tubular disorders, pregnancy, and drug-induced glycosuria, particularly in individuals receiving sodium-glucose cotransporter-2 inhibitors. Careful clinical assessment and laboratory evaluation are therefore essential to distinguish FRG from other pathological conditions that may require specific treatment or long-term monitoring [6,7].Most reported cases of familial renal glycosuria remain asymptomatic throughout life and demonstrate stable renal function with an excellent prognosis. However, the occurrence of additional urinary abnormalities may complicate the diagnostic process and raise concerns regarding the presence of concurrent renal, hepatic, or metabolic disorders [8,9]. The appearance of ketonuria or bilirubinuria in patients with longstanding isolated glycosuria has rarely been described in the literature, making such presentations diagnostically challenging [10].Recognition of familial renal glycosuria is important because misinterpretation of glycosuria may result in unnecessary investigations, inappropriate treatment, and patient anxiety. A detailed family history, normal glycemic profile, and preserved renal function can provide important clues toward establishing the diagnosis [11,12].We report a case of a 53-year-old male with a longstanding history of asymptomatic glycosuria and a positive family history suggestive of familial renal glycosuria, who subsequently developed new-onset ketonuria and bilirubinuria despite normal blood glucose levels and preserved renal function. This unusual presentation highlights the diagnostic challenges associated with atypical urinary findings in patients with presumed familial renal glycosuria