High Quality Content by WIKIPEDIA articles! Glycogen storage disease type II is a neuromuscular, autosomal recessive metabolic disorder in the family of lysosomal storage diseases caused by a deficiency in the enzyme Acid alpha-glucosidase, which is needed to break down glycogen long, branched glucose polymer and stored form of sugar used for energy. It is the only glycogen storage disease with a defect in lysosomal metabolism and was the first glycogen storage disease to be identified, in 1932. The build-up of glycogen causes progressive muscle weakness throughout the body and affects various body tissues, particularly in the heart, skeletal muscles, liver and nervous system. Pompe disease has historically been divided into three forms defined by age of onset and progression of symptoms. More recently there has been a trend to divide the disease into two groups: infantile onset and late onset.