Enzyme replacement therapy (NORD)

Enzyme replacement therapy, or ERT, is used in the treatment of some rare conditions that are caused by a congenital enzyme deficiency, that is, where a low enzyme level in the body causes problems such as muscle weakness, developmental delays, cognitive differences, and organ dysfunction. ERT replaces the missing enzyme and reduces symptoms, slows disease progression, and improves quality of life.  

Enzymes are proteins that help speed up processes in the body along a pathway, and each enzyme has a specific role in the body. When an enzyme level is low, forward progress in that particular pathway slows down or stops, causing substances to accumulate in a person’s cells. Storage of excess materials may damage cells, impairing their ability to function normally, resulting in dysfunction of organs such as the brain, liver, and heart.    

ERT is a therapy that can provide the specific enzyme a person is missing. It is usually administered by intravenous infusion and needs to be repeated frequently to keep the enzyme levels up because the enzyme is broken down in the body quickly.  However, other types of administration other than intravenous infusion are being studied. 

ERT is currently approved to treat some types of lysosomal storage diseases. Lysosomal storage diseases are caused by a change in a gene that results in reduced production of one of many lysosomal enzymes. Lysosomal enzymes help cells get rid of waste products. In Gaucher disease, for example, the enzyme level of glucocerebrosidase is low, and excess glucosylceramide accumulates in cells causing liver and spleen enlargement and blood abnormalities. ERT for Gaucher disease replaces glucocerebrosidase so the cells can once again get rid of excess waste products and therefore reduce symptoms of the disease.