Medicina Molecular e Genética

Discordant Symptoms in Monozygotic Twins with Huntington's Disease, Spinocerebellar Ataxia and other Neurodegenerative and Mendelian Disorders

Abstract

Burnham K

This is a review of nature (genetics) vs. nurture (environment in several genetically based conditions of the brain and nervous system. In the medical literature on twins similar symptoms and progression of the diseases are described as concordant. Symptoms that differ among identical twins are described as discordant. If a genetic condition like Huntington's disease is 100 percent influenced by genetics, then one would expect all Huntington's symptoms to be concordant. If some symptoms are discordant then they are attributed to the environment. Ways to describe these environmental factors include: non-genetic factors, epigenetics, nurture, stochastic (patterns that can't be predicted), pre and post-natal environment, lifestyle, and nutrition. These environmental factors are slightly different or hugely different even for identical twins. The environmental factors, especially lifestyle and nutrition are the factors most influenced by brain health coaches and complementary and alternative medicine practitioners. The literature supports the idea that even in Mendelian disorders (conditions that are thought of as primarily influenced by genetics) the environment, lifestyle, and nutrition can make large differences in the symptom picture and quality of life.