Slow, progressive myopathy in neonatally treated patients with infantile-onset Pompe disease: a muscle magnetic resonance imaging study

Background: Patients with infantile-onset Pompe disease (IOPD) can be identified through newborn screening, and the subsequent immediate initiation of enzyme replacement therapy significantly improves the prognosis of these patients. However, they still present residual muscle weakness. In the present study, we used longitudinal muscle magnetic resonance imaging (MRI) to determine whether this condition is progressive. Materials and methods: A cohort of classic IOPD patients who were diagnosed through newborn screening were treated with recombinant human acid a-glucosidase (rhGAA) and followed prospectively from birth. The trunk (and abdominal wall), pelvis and upper thighs were scanned for muscle MRI every 2-3 years. Seven groups of muscles were individually scored from 0 to 4 based on the extent of their involvement, and the sum was correlated to the clinical manifestations. Results: Twenty-four MRI scans from a total of 12 neonatally treated IOPD patients were analyzed in the present study. The median age at the time of MRI scanning was 4.2 years (13 days to 9 years). High intensity over the quadriceps on T2-weighted and short-tau inversion recovery images was observed in all scans and was followed by a decrease in muscle mass. Trunk muscle involvement was slower, except in one patient who exhibited progressive psoas atrophy. Among the 10 patients for whom follow-up scans were repeated more than 2 years after the first scan, four patients (40 %) showed increased myopathy severity. Conclusion: This prospective muscle MRI study provides evidence for the occurrence of slow, progressive muscle damage in neonatally treated IOPD patients during childhood. New treatment strategies are necessary to improve outcomes in these patients.