Essential tremor is a benign movement disorder, often confused with Parkinson disease. The prevalence of ET is estimated at 0.3-5.6% of the general population, and many affected individuals do not need treatment. It is usually inherited as an adult onset autosomal dominant trait, meaning there would be a 50% chance for children to inherit the condition from a parent. Although some studies have indentified associated genes, clinical genetic testing for essential tremor is not available.
About 1 in 1000 infants has profound hearing impairment, with half thought to be of genetic origin. Non genetic factors, such as prematurity, infection, and maternal exposures can also cause hearing loss. Several hundred genes are known to cause hereditary hearing loss and deafness, but the most common cause of hearing loss in American and European populations is a mutation in the connexin 26 (Cx26) gene.