Glycogen storage disease type IV, also known as Andersen disease, is a rare genetic disorder that affects the body's ability to break down glycogen, a stored form of glucose. This condition is caused by mutations in the GBE1 gene, which is responsible for producing an enzyme needed for glycogen branching. As a result, abnormal glycogen accumulates in various tissues, particularly in the liver and muscles. Symptoms of glycogen storage disease type IV can include liver enlargement, muscle weakness, and progressive liver disease. The severity of symptoms can vary widely among individuals. Early diagnosis and management are crucial, as the disease can lead to serious complications, including liver failure and other organ dysfunction.