Andersen disease belongs to a group of rare genetic disorders of glycogen metabolism, known as "glycogen storage diseases." Glycogen is a complex carbohydrate that is converted into the simple sugar glucose for the body's use as energy. Glycogen storage diseases are characterized by deficiencies of certain enzymes involved in the metabolism of glycogen, leading to an accumulation of abnormal forms or amounts of glycogen in various parts of the body, particularly the liver and muscle.
Andersen disease is also known as glycogen storage disease (GSD) type IV. It is caused by deficient activity of the glycogen-branching enzyme, resulting in accumulation of abnormal glycogen in the liver, muscle, and/or other tissues. In most affected individuals, symptoms and findings become evident in the first months of life. Such features typically include failure to grow and gain weight at the expected rate (failure to thrive) and abnormal enlargement of the liver and spleen (hepatosplenomegaly). In such cases, the disease course is typically characterized by progressive liver (hepatic) scarring (cirrhosis) and liver failure, leading to potentially life-threatening complications. In rare cases, however, progressive liver disease may not develop. In addition, several neuromuscular variants of Andersen disease have been described that may be evident at birth, in late childhood, or adulthood. The disease is inherited as an autosomal recessive trait.
