Genes are the instructions contained in all of the cells in the body, which control cell function. Occasionally spelling mistakes in these genes can lead onto an increased risk of developing specific diseases. For some conditions such as Alzheimer disease, the identification of rare inherited forms of these diseases has led on to the identification of gene abnormalities and the development of new cell and animal models which can act as a test bed for new treatments. The main clue to the presence of a faulty gene is the occurrence of families in which many people have been affected by a specific medical condition.
For essential tremor there is a wide range in the estimates of the risk to other family members, when a single person has been affected. In general terms, people with a young age at onset and essential tremor, often have a family history of others affected with the same condition, whereas those who develop essential tremor later in life are less likely to have a familial disease.
We know that in studies of twins with essential tremor, about 60% of identical twins will have both twins affected with tremor, as opposed to about 30% of non-identical twins. Although a lot of progress has been made in identifying potential genetic areas which might harbor genes that cause essential tremor, very little progress has been made in identifying the specific genes.
Adapted from Dr Huw Morris, Neurologist presentation at the NTF AGM (2009)