Therapy of genetic diseases: a three-level approach

Therapy of genetic diseases may be attempted at three different levels in the evolution of the disease process. At the first level, after clinical manifestations have appeared, methods are symptomatic and include diet, drugs, surgery, and avoidance of hazardous substances. At the second level, midway between the origin of the disease and the appearance of clinical manifestations, therapy consists of administration of a normal gene product, such as insulin in diabetes and factor VIII in hemophilia. At the third level, the origin of the disease, methods involve correcting the gene defect and are currently under investigation.