Several neuromuscular variants of Andersen disease (GSD4) have been described. These may be evident at birth, in late childhood, or adulthood. Deficient activity of the glycogen-branching enzyme is the cause of GSD4. It results in accumulation of abnormal glycogen in the liver, muscle and other tissues.

In the perinatal variant, usually symptoms become apparent in the first few months of a baby’s life. Such signs typically include failure to thrive – slow growth and failure to gain weight at the expected rate. There may be an abnormally large liver and spleen. There is typically progressive liver scarring and liver failure, leading to life-threatening complications, but in some cases progressive liver disease does not develop.

Children: GSD4 is a very severe but rare disorder. No treatment apart from liver transplantation has been found to prevent progression of the disease. Most children with this condition die before two years of age.

Adults: Patients with adult polyglucosan body disease APBD have deficient glycogen-branching enzyme activity, diffuse CNS and peripheral nervous system dysfunction.