Familial Neurodegenerative Diseases and Single Nucleotide Polymorphisms

Neurology is a discipline rich in the study of inherited disorders. Most of these studies have focused on diseases in which changes in a single gene are severe enough to cause a disease by themselves. Examples of such changes are mutations in the dystrophin gene that lead to Duchenne muscular dystrophy, or triplet repeat expansions that lead to Huntington disease. However, as well-known as these examples are, they do not reflect the majority of the diseases that the average physician experiences in his or her practice. Most common disorders have important genetic components, but they are not as obvious. Rather, each contributes a smaller amount of risk, and may require environmental interactions to produce symptoms. The elucidation of these genetic elements has the potential to radically change the way all physicians practice medicine in the future. In this chapter we will begin to explore the nature of these genetic changes (complex genetics) and current knowledge of their contribution to several common neurodegenerative disorders.