Effect of long term enzyme replacement therapy in late onset Pompe disease: A single-centre experience

Late onset Pompe disease (LOPD) is a slowly progressive metabolic myopathy with variable clinical severity. The advent of enzyme replacement therapy (ERT) has modified the natural course of the disease, though the treatment effect on adult patients is modest compared to infants with the classic form. This study aims to describe the long-term clinical outcome of the Greek LOPD cohort, as assessed by 6 min walk test, muscle strength using MRC grading scale and spirometry. ERT efficacy was estimated using statistical methodology that is novel in the context of Pompe disease, which at the same time is well-suited to longitudinal studies with small samples and missing data (local non-linear regression analysis). Improvement over baseline was significant at 1 year for motor performance and muscle strength (p < 0.05), and at 2 years for FVC-U and FVC-S (p < 0.05). A subgroup analysis showed that the onset of the disease before adulthood (18 years), a male gender, and a latency of more than 2 years between the onset of symptoms and ERT administration are unfavorable prognostic factors. Conclusively, this study presents longitudinal data from the Greek LOPD cohort supporting previous observations, that therapeutic delay is related to worse prognosis and treatment effects may decline after several years of ERT.