Abstract
Pegvaliase (Palynziq®) was FDA approved in 2018 as an enzyme substitution therapy in patients with Phenylketonuria. However, various drug induced hypersensitivity adverse events (HAEs) have been reported. We present a case of Pegvaliase (Palynziq®) induced anaphylaxis and successful desensitization. A 13-step desensitization protocol was performed using three solution concentrations of Palynziq with premedication of diphenhydramine and prednisone in an outpatient setting. The patient tolerated the desensitization and was able to continue Palynziq.