Alpelisib-Induced Diabetic Ketoacidosis in a Non-diabetic Patient

Alpelisib is a phosphoinositol-3-kinase alpha catalytic subunit (PIK3CA) inhibitor used in patients with PIK3CA mutated breast cancer. The phosphatidylinositol 3-kinase (PI3K) pathway is responsible for activating protein kinase-B (AKT), and activated AKT promotes translation of glucose transporter 4 and glycogen synthesis in insulin-responsive tissues. Therefore, it is perhaps not surprising that hyperglycemia is the most common side effect of alpelisib, though diabetic ketoacidosis (DKA) appears to be a rare complication. This case describes the unique presentation of a patient with no prior history of diabetes who presented with DKA after starting alpelisib, and returned to euglycemia off of insulin just three days after stopping the drug suggesting that alpelisib can cause DKA in patients who did not previously have diabetes, and that the hyperglycemia is completely reversible upon discontinuation of the PIK3CA inhibitor and consequent restoration of the PI3K/AKT pathway.