Canagliflozin-induced Fanconi syndrome in a patient with previously unrecognized type 1 diabetes.

PURPOSE: Canagliflozin is a sodium-glucose cotransporter-2 (SGLT2) inhibitor which received U.S. Food and Drug Administration approval in 2013 for the treatment of type 2 diabetes mellitus. Fanconi syndrome is a rare acquired disorder which typically occurs in adults as an adverse effect of medications. The literature includes few case reports of Fanconi syndrome caused by the use of canagliflozin. Here, we present a case of Fanconi syndrome in a patient with type 1 diabetes previously miscategorized as type 2 diabetes.

SUMMARY: A 32-year-old woman with a 6-year history of type 2 diabetes was started on canagliflozin. Within 2 months of therapy initiation, she began to develop symptoms of high anion gap metabolic acidosis. Further laboratory test results showed severe life-threatening hypophosphatemia. Further investigation by nephrology revealed the presence of Fanconi syndrome. During the admission, she was found to have clinical and laboratory features of type 1 (insulin-dependent) diabetes. After discontinuation of canagliflozin, she was treated with intravenous (i.v.) fluids for hydration, subcutaneous insulin, and i.v. potassium phosphate. She recovered from all metabolic acidosis and electrolyte abnormalities.

CONCLUSION: Fanconi syndrome is a rare, exogenously acquired disorder in adults that often develops as an adverse effect of medication therapy. Our patient presented with Fanconi syndrome as a complication of canagliflozin use for the treatment of presumed type 2 diabetes. She was then started on subcutaneous insulin monotherapy for the treatment of type 1 diabetes mellitus.