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