Long‐term follow‐up of 64 children with classical infantile‐onset Pompe disease since 2004: A French real‐life observational study

Abstract Background Classical infantile‐onset Pompe disease (IOPD) is the most severe form of Pompe disease. Enzyme replacement therapy (ERT) has significantly increased survival but only a few studies have reported long‐term outcomes. Methods We retrospectively analyzed the outcomes of classical IOPD patients diagnosed in France between 2004 and 2020. Results Sixty‐four patients were identified. At diagnosis (median age 4 months) all patients had cardiomyopathy and most had severe hypotonia (57 of 62 patients, 92%). ERT was initiated in 50 (78%) patients and stopped later due to being ineffective in 10 (21%). Thirty‐seven (58%) patients died during follow‐up, including all untreated and discontinued ERT patients, and 13 additional patients. Mortality was higher during the first 3 years of life and after the age of 12 years. Persistence of cardiomyopathy during follow‐up and/or the presence of heart failure were highly associated with an increased risk of death. In contrast, cross‐reactive immunologic material (CRIM)‐negative status ( n = 16, 26%) was unrelated to increased mortality, presumably because immunomodulation protocols prevent the emergence of high antibody titers to ERT. Besides survival, decreased ERT efficacy appeared after the age of 6 years, with a progressive decline in motor and pulmonary functions for most survivors. Conclusions This study reports the long‐term follow‐up of one of the largest cohorts of classical IOPD patients and demonstrates high long‐term mortality and morbidity rates with a secondary decline in muscular and respiratory functions. This decreased efficacy seems to be multifactorial, highlighting the importance of developing new therapeutic approaches targeting various aspects of pathogenesis.