Enzyme replacement therapy (ERT) is a type of medical treatment used to replace enzymes that are missing or not working properly in the body. It is used to treat a variety of genetic disorders, including lysosomal storage diseases, such as Gaucher disease, Fabry disease, and Pompe disease. ERT involves the intravenous administration of a recombinant enzyme, which is a laboratory-made version of the enzyme that is missing or not working properly in the body. The enzyme helps to break down substances that would otherwise accumulate in the body, leading to symptoms and complications.