Early pathologic changes and responses to treatment in patients with later-onset Pompe disease

The treatment of later-onset Pompe disease with enzyme replacement therapy may not lead to significant improvement in muscle function, probably because of the irreversible muscle destruction caused by glycogen storage. A prospective study was performed to understand early muscle pathology in patients and the response of these pathologic changes to treatment. Five newborns and one child with later-onset Pompe disease but no signs at time of diagnosis were prospectively followed, and treatment was initiated when signs appeared. Six pretreatment biopsies taken at ages 1.5 months to 7 years indicated glycogen storage, lipid storage, stage 4 myocytes, and autophagic debris. Four 6-month posttreatment biopsies revealed glycogen clearance, but stage 4 myocytes and autophagic debris were still evident in three. In conclusion, among patients with later-onset Pompe disease and very mild signs, advanced pathologic changes were evident in a small portion of their myocytes. Because these pathologic changes may not respond to treatment, early treatment is necessary to achieve the best outcomes.