Whole Body Muscle MRI Correlates with Muscle Function in Patients with Adult Onset Pompe Disease

Adult onset Pompe disease is a genetic disorder produced by mutations in the AAG gene and clinically characterized by slowly progressive weakness of the limbs and respiratory muscles. Treatment, with enzyme replacement, can improve or stabilize muscle function. Our aim is to investigate whether the degree of muscle atrophy in whole body MRI correlates with muscle function in patients with adult onset Pompe patients. A complete clinical evaluation including physical examination, muscle functional studies, respiratory assessment, quality of life scales and whole muscle MRI was performed to all patients. We analyzed the degree of muscle atrophy on T1 sequences using Mercuri scale. We defined muscle MRI score as the sum of Mercuri scale for all muscles of the body. To analyze correlation between two values, we used the Pearson test considering statistically significant p value lower than 0.05. We enrolled 30 patients (17 women, 53%). Mean age at inclusion was 46.2 years old (range 8–66 years old). 25/30 patients had weakness and 5/30 patients had only hyperckemia. Twenty-two of the 25 patients symptomatic were under treatment with ERT. Muscle MRI score patients ranged from 0 to a maximum of 210 points. There was a positive correlation between muscle MRI score and the following parameters: muscle strength (measured using MRC scale or hand held myometry), muscle function tests (MFM-20 scale, time to climb and to descend 4 steps, 6MWT, Activlim scale) and quality of life scales (sf36 and Inquol). In contrast muscle MRI did not correlate significantly with respiratory function (p > 0.05). The degree of muscle atrophy in muscle MRI studies has a good correlation with muscle strength, muscle functional scales and quality of life scales in adult onset Pompe patients. Based on our results, muscle MRI could be useful to follow up patients under treatment to know if they are responding well to the drug and muscle MRI could be a good end-point objective in clinical trials.