Glycogen storage disease due to glycogen branching enzyme deficiency, childhood neuromuscular form

Glycogen storage disease due to glycogen branching enzyme deficiency, childhood neuromuscular form, is a rare subtype of glycogen storage disease type IV (GSD IV), also known as Andersen disease or amylopectinosis. It is caused by mutations in the GBE1 gene, which encodes the glycogen branching enzyme (1,4-alpha-glucan-branching enzyme). Deficiency of this enzyme leads to the accumulation of an abnormal, poorly branched glycogen (resembling amylopectin or polyglucosan) in affected tissues, particularly skeletal muscle and peripheral nerves. The childhood neuromuscular form typically presents in later childhood with progressive skeletal muscle weakness (myopathy) and may involve peripheral neuropathy. Affected children may experience exercise intolerance, proximal and distal muscle weakness, and reduced deep tendon reflexes. Unlike the classic severe infantile hepatic form of GSD IV, this subtype tends to spare the liver or involve it to a lesser degree, with the primary burden falling on the neuromuscular system. Cardiac involvement may also occur in some cases. Disease progression is variable but can lead to significant motor disability over time. There is currently no specific curative treatment for this condition. Management is primarily supportive and multidisciplinary, involving physical therapy to maintain muscle function, monitoring of cardiac and respiratory status, and nutritional support as needed. Liver transplantation, which has been used in the classic hepatic form, is generally not indicated for this subtype. Research into enzyme replacement therapy and gene therapy is ongoing but no approved disease-specific therapies are currently available.

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