As stated previously, Essential Tremor can tend to run in families and in those cases is most definately caused by a faulty gene.
Members of a large family of Czechoslovakian descent, who live in America, became known as the 'Iowa Kindred' in an attempt to protect their privacy. All members of this extended family develop either Parkinson's Disease or Essential Tremor. The fact that all members developed either condition has led some researchers to consider that the two forms of tremor may indeed be related but at the time of writing this has not been proved.
In this particular family Parkinson's and tremor typically begin at a relatively early age with the average age being 34 years but ranging between 20 - 48 years.
Laboratory tests and post mortem studies showed the family all share the same mutant gene which leads researchers to think that there may be some form of relationship between Parkinson's and Essential Tremor after all. Initially the researchers were looking for the typical alpha-synuclein mutation involved in Parkinsonian type symptoms but they became dismayed when they couldn't find the mutant gene they expected to be present. Further examination showed what they initially thought to be a previously undiscovered gene and the scientists even coined a new name, Park 4, for what they thought to be a completely different genetic mutation. However, on further examination of post mortem studies of the Iowa Kindred they did find the responsible alpha-synclein gene they initially expected to find but instead of the usual two copies involved in Parkinson's they actually found 4 copies