Combined omalizumab and desensitization to control IgE-mediated hypersensitivity in enzyme replacement therapy for late-onset Pompe disease

Background: Pompe disease is a rare, progressive lysosomal storage disorder caused by acid α-glucosidase deficiency, leading to glycogen accumulation, proximal muscle weakness, and respiratory decline. Enzyme replacement therapy (ERT) significantly improves survival and stabilizes motor function, but IgE-mediated hypersensitivity reactions (HSRs) can critically compromise treatment, posing a major clinical challenge. Desensitization protocols allow temporary tolerance to ERT, yet breakthrough reactions may occur, necessitating adjunctive strategies such as omalizumab. Results: We report a 40-year-old woman with late-onset Pompe disease who developed severe IgE-mediated HSRs to alglucosidase alfa after years of uneventful therapy. Basophil activation testing (BAT) and serum-specific IgE confirmed an IgE-mediated mechanism. A 15-step, 5-bag desensitization protocol allowed temporary tolerance, but breakthrough reactions required therapy interruption. Upon switching to avalglucosidase alfa, BAT demonstrated IgE cross-reactivity, and a new desensitization protocol was implemented. Initial infusions were complicated by recurrent HSRs. The addition of subcutaneous omalizumab (300 mg monthly), administered two days before ERT, enabled safe reintroduction. Moreover, therapy was resumed gradually, starting at 50% of the target dose and escalating stepwise to the full therapeutic dose, resulting in uninterrupted treatment. Follow-up showed stable neuromuscular and respiratory function, progressive decline in BAT reactivity, and improved quality of life. Conclusions: This case highlights the critical role of BAT in diagnosing and monitoring IgE-mediated HSRs, the efficacy of individualized desensitization protocols, and the utility of omalizumab as an adjunctive therapy in refractory cases. In rare diseases like Pompe, documenting such integrated allergological strategies provides practical guidance for maintaining access to life-prolonging therapy and offers a reproducible framework for managing complex allergic complications.