Pompe disease is an inherited autosomal recessive glycogen storage disease caused by partial or total deficiency of acid α-glucosidase (GAA), resulting in the accumulation of glycogen in the lysosomes of skeletal muscles, heart, liver and other tissues. There is an inverse correlation between the amount of residual GAA activity and disease severity. The clinical phenotype varies with regard to age of onset, organ involvement, and severity of progression. In 2006, enzyme replacement therapy (ERT) with recombinant human GAA (Genzyme Corporation, Cambridge MA, USA) was approved and, since then, decisive modification of the course of the disease has been reported. Clinical studies in infants showed that ERT led to improvement in cardiac, respiratory and skeletal muscle functions, with achievement of independent walking, higher levels of physical activity, and survival beyond infancy.