Alpelisib-Induced Diabetic Ketoacidosis in a Patient With Metastatic Breast Cancer

We report the case of a 45-year-old woman with metastatic breast cancer who started treatment with alpelisib nine days before developing diabetic ketoacidosis (DKA). At the time of DKA diagnosis, blood tests showed a capillary blood glucose of 30 mmol/L, serum carbon dioxide level of 11 mmol/L, an anion gap of 25 mEq/L, and a glycated hemoglobin A1C (HbA1c) level of 6.4% (50 mmol/mol). Her HbA1C on admission was 5.6% (38 mmol/mol). Capillary blood glucose levels improved upon discontinuation of alpelisib and returned to baseline four days after drug discontinuation. DKA is a rare but serious adverse effect of alpelisib. Patients on this medication should be closely monitored for hyperglycemia and DKA. Further studies are needed to help identify patients at risk of hyperglycemia and DKA.