Family Screening for Genetic Disorders: Lessons from Huntington’s Disease

Abstract

The presymptomatic detection of serious genetic disorders is well established in clinical practice and has been feasible for a number of conditions since long before the new developments in molecular genetics. In some cases, such as testing for phenylketonuria by serum phenylalanine level at birth, there is a direct and profound effect on the outlook for affected individuals, and effective dietary treatment is available. In other situations, such as the neonatal detection of Duchenne muscular dystrophy by serum creatine kinase in a family at risk, the benefits for the affected boy are less clearly defined, but the testing may have major consequences for the risks to future children and other family members. Such examples have however remained relatively few, and most of the serious genetic disorders of late onset have no early detectable phenotypic effects; it is here that our increasing ability to identify disease genes, or polymorphic genetic markers closely linked to them, is creating possibilities for prediction that require careful consideration if more harm than good is not to result.