Evaluation of muscle biopsy in late-onset GSDII patients before and after enzyme replacement therapy (ERT)

Introduction Glycogen storage disease, glycogenosis type II (GSDII), or Pompe disease (OMIM 23230), is an autosomal recessive lysosomal storage disorder that results from a deficiency in the acid alpha glucosidase (GAA) enzyme. The disease is characterized by progressive accumulation of lysosomal glycogen in various tissues, primarily in cardiac and skeletal muscles. The histopathological hallmarks in the muscle are fiber vacuolization and autophagy. GSDII is clinically classified as a severe infantile, or an attenuated, later-onset form affecting children and adults. Recombinant human GAA (rhGAA) is the only approved enzyme replacement therapy (ERT) available for the treatment of Pompe disease, and it is effective in infantile patients, whereas in adults, improvements are more variable among different patients. Our project aims to assess the effects of ERT in 19 late-onset patients using both biochemical and morphological (histological, histochemical, and immunohistochemical) evaluations of skeletal muscle biopsies before and after 6 months to 1 year on ERT.