Muscle weakness is the main symptom of Pompe disease, a lysosomal storage disorder for which major clinical benefits of enzyme replacement therapy (ERT) have been documented recently. Restoration of skeletal muscle function is a challenging goal. Type 2 muscle fibers of mice with Pompe disease have proven resistant to therapy. To investigate the response in humans, we studied muscle biopsies of a severely affected infant before and after 17 months of therapy. Type 1 and 2a fibers were marked with antibodies, and lysosome-associated membrane protein-1 (Lamp1) was used as the lysosomal membrane marker. Quantitative measurements showed a 2.5-3-fold increase of fiber cross-sectional area of both fiber types during therapy and normalization of the Lamp1 signal in ∼95% of type 1 and ∼75% of type 2a fibers. The response of both type 1 and 2a muscle fibers in the patient studied herein corroborates the beneficial effects of enzyme therapy seen in patients with Pompe disease.

Acid maltase deficiency, Enzyme therapy, Glycogenosis, Lysosomal storage disorder, Muscle-fiber size, Pompe disease,
Muscle & Nerve
Erasmus MC: University Medical Center Rotterdam

Drost, M.R, Schaart, G, van Dijk, P, van Capelle, C.I, van der Vusse, G.J, Delhaas, T, … Reuser, A.J.J. (2008). Both type 1 and type 2a muscle fibers can respond to enzyme therapy in Pompe disease. Muscle & Nerve, 37(2), 251–255. doi:10.1002/mus.20896