Essential tremor (ET) is one of the most common movement disorders seen in routine neurological practice, but other diseases may mimic this condition. Here we describe a 62-year-old right-handed man with an action (kinetic) tremor fulfilling diagnostic criteria for ET which was the presenting feature of the fragile X associated tremor/ataxia syndrome. His sister’s grandchildren were the clue to the diagnosis, illustrating the importance of a detailed medical history in descendents as well as ancestors in the context of late onset neurological disorders.

ET, typically a symmetric bilateral postural tremor with fluctuating amplitude, can be asymmetric and varies both in severity and functional impact. It classically begins in the fourth and fifth decades of life, is frequently associated with a family history and affects 0.8/1000 (95% confidence interval 0.5 to 1) of the general population, with a prevalence that increases with age.1 ET is one of the most common movement disorders seen in routine neurological practice, and the diagnosis is usually straightforward. The …