• Source: Glycogen storage disease type IV

      • Glycogen storage disease type IV (GSD IV), or Andersen's Disease, is a form of glycogen storage disease, which is caused by an inborn error of metabolism. It is the result of a mutation in the GBE1 gene, which causes a defect in the glycogen branching enzyme. Therefore, glycogen is not made properly and abnormal glycogen molecules accumulate in cells; most severely in cardiac and muscle cells. The severity of this disease varies on the amount of enzyme produced. GSD IV is autosomal recessive, which means each parent has a mutant copy of the gene, but show no symptoms of the disease. Having an autosomal recessive inheritance pattern, males and females are equally likely to be affected by Andersen's disease. Classic Andersen's disease typically becomes apparent during the first few months after the patient is born. Approximately 1 in 20,000 to 25,000 newborns have a glycogen storage disease. Andersen's disease affects 1 in 800,000 individuals worldwide, with 3% of all GSDs being type IV. The disease was described and studied first by Dorothy Hansine Andersen.


      Human pathology


      It is a result of the absence of the glycogen branching enzyme, which is critical in the production of glycogen. This leads to very long unbranched glucose chains being stored in glycogen. The long unbranched molecules have low solubility, leading to glycogen precipitation in the liver. These deposits subsequently build up in the body tissue, especially the heart and liver. The inability to break down glycogen in muscle cells causes muscle weakness. The probable result is cirrhosis and death within five years. In adults, the activity of the enzyme is higher and symptoms do not appear until later in life.


      Variant types




      = Fatal perinatal neuromuscular type

      =
      Excess fluid builds up around and in the body of the fetus
      Fetuses exhibit fetal akinesia deformation sequence
      Causes decrease in fetal movement and stiffness of joints after birth
      Infants have low muscle tone and muscle wasting
      Do not survive past the newborn stage due to weakened heart and lungs


      = Congenital muscular type

      =
      Develops in early infancy
      Babies have dilated cardiomyopathy, preventing the heart from pumping efficiently
      Only survive a few months


      = Progressive hepatic type

      =
      Infants have difficulty gaining weight
      Develop enlarged liver and cirrhosis that is irreversible
      High BP in hepatic portal vein and buildup of fluid in the abdominal cavity
      Die of liver failure in early childhood


      = Non-progressive hepatic type

      =
      Same as progressive, but liver disease is not so severe
      Do not usually develop cirrhosis
      Usually show muscle weakness and hypotonia
      Survive into adulthood
      Life expectancy varies upon symptom severity


      = Childhood neuromuscular type

      =
      Develops in late childhood
      Has myopathy and dilated cardiomyopathy
      Varies greatly
      Some have mild muscle weakness
      Some have severe cardiomyopathy and die in early adulthood


      Diagnosis


      An assay of amylo-1,4 → 1,6 glucan transferases (which removes a block of 6 glucose residues from the 1,4 position and attaches it to the 1,6 position of the same chain)


      Alternative names and related disease


      Alternative names in medical literature for the disease include:

      Andersen's triad
      Glycogenosis type IV
      Glycogen branching enzyme deficiency
      Polyglucosan body disease
      Amylopectinosis
      Mutations in GBE1 can also cause a milder disease in adults that is called adult polyglucosan body disease.


      In other mammals


      The form in horses is known as glycogen branching enzyme deficiency. It has been reported in American Quarter Horses and related breeds.
      The disease has been reported in the Norwegian Forest Cat, where it causes skeletal muscle, heart, and CNS degeneration in animals greater than five months old. It has not been associated with cirrhosis or liver failure.


      References




      External links


      Media related to Glycogen storage disease type IV at Wikimedia Commons

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