An international team of researchers has identified a single gene that promotes development of essential tremor in some patients and Parkinson's disease in others.
In a study report published in Parkinsonism and Related Disorders, Mayo Clinic researchers in Florida and their collaborators worldwide note that patients with essential tremor shake when they move, while those with Parkinson's disease shake when they are at rest.
They further state that a variant in LINGO1, a gene involved in neuronal survival, is the first proven evidence of a common genetic component in the development of both disorders.
Analysing their findings, the researchers have come to the conclusion that mutations in this gene are potentially responsible for five percent of patients with Parkinson's disease, and five percent of patients with essential tremor.
Lead researcher Dr. Carles Vilarino-Guell, of Mayo Clinic, said: "There is a mutation in the gene that must be causing or contributing to Parkinson's disease in some people and essential tremor in others."
He, however, added that that did not mean that people with essential tremor have an increased risk of developing Parkinson's disease.
The findings are intriguing because "although essential tremor and Parkinson's disease are considered to be different diseases, researchers have been arguing for a long time about whether essential tremor is a milder, preliminary form of Parkinson's disease, and they have been looking for the genetic connection between these disorders," he said.
"Now we know LINGO1 is the first gene identified," he added.
The scientists have yet to identify any specific mutation or mutations on LINGO1 responsible for either disorder.
"The easiest explanation is that there are two separate and clearly distinct mutations in the gene contributing to the disorders. But because this gene doubles the risk of developing either disease and it is found at the same frequency in both diseases, it is possibly the same mutation," Dr. Vilarino-Guell said.
"Both diseases are also affected by environmental factors, and that may influence which disorder a person would be more likely to develop," he added.