Effect of Enzyme Replacement Therapy in Patients With Juvenile-onset Pompe Disease

Pompe disease is known as glycogen storage disease type II, an autosomal recessive disease that results from acid alpha-glucosidase (GAA) deficiency leading to lysosomal glycogen accumulation. Patients with classic infantile form have less than 1% of enzyme activity, which explains severe impairment before one year with rapid death without treatment, while later-onset form shows progressive symptoms later in childhood (juvenile form) or adulthood (adult form). Enzyme replacement therapy (ERT) consists of periodic intravenous infusion of missing GAA produced by the recombinant method. ERT improves significantly the cardiac function and the children's survival in classic infantile form. This therapy has been approved for all patients with Pompe's disease in the United States and the European Union since 2006, but its efficacy was not clear for patients with later-onset form. Recent studies show motor improvement in adult patients, but there is little published data for the juvenile form disease. A separate analysis of juvenile form is justified as patients are still in a developmental stage and show clinical symptoms early in life, may have more severe disease and a different response to ERT. The recommendation is no treatment in the absence of clinical symptoms, but the consensus does not stratify patients into juvenile- or adult-onset form. ERT is an expensive long-term therapy, and its administration every 2 weeks in the hospital is a great limitation for patients. Therefore, an evaluation of the treatment effect in patients with the juvenile form is necessary.