We describe a case of the juvenile form of glycogen storage disease type II or Pompe's disease, confirmed by muscle biopsy and electrodiagnostic study. This autosomal recessively inherited disease is characterized by the presence of vacuoles of varying size in most muscle fibers. In addition to proximal muscular weakness and hypotonia, the clinical feature include cardiomegaly, hepatomegaly, enlargement of the tongue. Death occurs in 30% of cases in childhood from respiratory muscle weakness.

This glycogen storage disease type II can be divided into three form, such as the severe infantile form, a milder childhood form and adult onset form. EMG findings in Pompe's disease usually show myopathic feature. A muscle biopsy in this case has shown the prominent findings of vacuolar change with degenerated muscle fibers and distorsioning muscle achitecture containing glycogen particles, which revealed glycogen storage disease.