 It was not until the early 1980s, where researchers could determine the actual cause of cystic fibrosis, being - a single mutation causing incomplete synthesis of a transmembrane protein, resulting in thick, clogging secretions mainly in the pancreas and respiratory tract.In addition to her research on cystic fibrosis, Dorothy Hansine Andersen also initially investigated and described a rare glycogen storage disease, glycogen storage disease type IV (GSD IV) also known as Andersen's disease.It is caused by a lack of activity in glycogen-branching enzyme resulting in accumulation of glycogen in the liver.