Hypersensitivity Reaction and a Single‐Bag Rapid Desensitization to Idursulfase

Idursulfase is the first-line and only available enzyme replacement therapy (ERT) for Mucopolysaccharidosis type II (MPS II), or Hunter Syndrome. Deficiency in the lysosomal enzyme iduronate-2-sulfatase leads to progressive skeletal deformities, neurologic deterioration, airway obstruction, and cardiomyopathy. In severe cases, these deformities can lead to death during teenage years (Stapleton et al. 2017). Continuous treatment with ERT is essential to prevent irreversible changes. However, 16 out of 108 (15%) patients had hypersensitivity reactions to idursulfase during clinical trials. Hypersensitivity reactions have also been reported several years into treatment (Elaprase 2018). Therefore, it is critical to evaluate for hypersensitivity reactions and desensitize patients to idursulfase. We report a fourteen-year-old male who was evaluated using a nonirritating skin test concentration and underwent a novel desensitization protocol for Lysosomal Storage Disease ERT.