Glycogen storage disease type IV (GSD4)

Glycogen storage disease type IV (GSD IV) of the Norwegian forest cat is an inherited abnormality of glucose metabolism. Normally, excess glucose is stored in many tissues as glycogen. If energy is needed, glucose molecules are removed from glycogen. The ability to add and remove glucose molecules from glycogen efficiently is dependent on its highly branched structure. The glycogen branching enzyme (GBE) is an enzyme of glycogen synthesis necessary to produce the branching structure. Deficiency of GBE activity leads to abnormal glycogen accumulation in myocytes, hepatocytes, and neurones, causing variably progressive, benign to lethal organ dysfunctions. Most affected kittens die at or soon after birth, presumably due to hypoglycemia. Survivors of the perinatal period appear clinically normal until onset of progressive neuromuscular degeneration at 5 month of age.