Quantitative magnetic resonance imaging in late-onset Pompe disease: A prospective observational study of 19 patients

Late-onset Pompe disease (LOPD) is an autosomal recessive disorder characterized by progressive weakness of skeletal and respiratory muscles. Enzyme replacement therapy (ERT) has changed LOPD natural history; it is not known whether ERT stops the progression of the disease. Our aim was to study progression of fatty degeneration in muscles in LOPD patients using 3 point Dixon imaging software. This is a prospective observational study in which we performed muscle MRI using T1w and 3 point Dixon imaging at basal and at 1 year visit. The presence of fat tissue in skeletal muscles in T1w imaging sections was studied using Mercuri scale. 3 point Dixon studies were performed on paraspinal and thighs muscles. 19 LOPD patients were recruited. 4 untreated presymptomatic patients (24.2 yo, 8 – 49) and 15 symptomatic LOPD patients (51.5 yo, 31 – 66) were included in the study. 13 symptomatic patients were under treatment (mean time = 3.7 y). We did not detect changes in T1-weighted MRI sequences at year 1 compared to basal visit. In contrast, 3 point Dixon imaging showed a mean increase on fat infiltration in skeletal muscles of 2.32%, that was not significant. We only observed significant changes in semimembranous muscle (SM) (2.51%; p = 0.049), while there were not significant changes on the rest of the muscles analyzed. We studied the group of symptomatic treated patients and detected a significant increase on fat infiltration in SM muscle (3.18%; p = 0.03) and a tendency to increased fatty deposition on biceps femorii long head (1.76%; p = 0.056). In the 4 presymptomatic patients, there was a non-significant decrease on the percentage of fat in thigh muscles. 3 point Dixon imaging technique is more sensitive to detect mild changes in the quantity of fat tissue in muscles than T1w imaging in LOPD. We observed a mild increase in fat tissue only in SM muscle in treated patients, while the amount of fat tissue did not significantly changed in the rest of muscles of trunk and thighs.