Glycogen storage disease due to acid maltase deficiency, late-onset

A form of glycogen storage disease due to acid maltase deficiency characterized by excessive accumulation of glycogen in lysosomes most notably in skeletal muscle, leading to slowly progressive muscle weakness with walking disability and reduced respiratory function. The late-onset form includes all cases in which hypertrophic cardiomyopathy did not manifest or was not diagnosed at or under the age of 1 year, as well as all cases with symptom onset above the age of 1 year.