Background and purpose: Data on interruption of enzyme replacement therapy (ERT) are scarce in late onset Pompe disease. Due to the COVID‐19 crisis, eight neuromuscular reference centers in France were obligated to stop the treatment for 31 patients. Methods: We collected the motor and respiratory data from our French registry, before COVID‐19 and at treatment restart. Results: In 2.2 months (mean), patients showed a significant deterioration of 37 m (mean) in the 6‐min walk test and a loss of 210 ml (mean) of forced vital capacity, without ad integrum restoration after 3 months of ERT restart. Conclusions: This national study based on data from the French Pompe Registry shows that the interruption of ERT, even as short as a few months, worsens Pompe patients' motor and respiratory function. [ABSTRACT FROM AUTHOR]