Gaucher disease is an inherited functional deficiency of glucocerebrosidase. This enzyme breaks down a fatty substance (lipid) called glucocerebroside, which is present in all cells of the body. When cells renew themselves, the lipids must be broken down and discarded. Because the enzyme does not function well, the lipid builds up in certain tissues, such as the liver and spleen. The nervous system is involved as well; memory is impaired and it is difficult to move the eyes from side to side. It has been shown that repeated infusions of glucocerebrosidase help break down the stored lipid. However, this treatment does not improve any neurological symptoms.