<h4>Background</h4>Sodium-glucose cotransporter 2 inhibitors (SGLT-2i) have proven benefits in patients with biventricular heart failure; however, their role in patients with univentricular physiology and failing Fontan circulation (FC) remains largely unexplored.<h4>Clinical presentation</h4>A 21-year-old male with failing FC, preserved ejection fraction, and protein-loosing enteropathy (PLE) presented to our Adult Congenital Heart Disease Unit for evaluation. This evidence concerns the gene SLC5A2 and heart disorder.