Fragile-X syndrome

Fragile-X syndrome is the most common inherited cause of learning disability worldwide, with a prevalence of 1 in 4000 males and 1 in 8000 females. It is caused by a mutation of the FMR-1 (fragile-X mental retardation) gene located on the X chromosome. This contribution explores the genetic and molecular basis of the disease and methods for its detection, as well as neuropathological findings. The issues involved in genetic counselling and screening are also discussed. The presentation of fragile-X syndrome is variable, but common physical, behavioural and developmental features are outlined. The specific deficits, in terms of learning disability, are also explored; for example, males with fragile-X syndrome have particular difficulties in sequential processing of information. Broad differences between male and female learning disability have also been discovered. The relationship between fragile-X syndrome and autistic spectrum disorders is mentioned, as are comorbidities with other neurological (epilepsy) and psychiatric disorders. There is no definitive treatment for fragile-X syndrome, but a number of interventions can raise the quality of life of the individual and their family and carers. These include medical therapy for comorbid conditions such as epilepsy and attention deficit hyperactivity disorder, as well as behavioural and cognitive interventions. However, there is still much scope for new research into both the molecular basis and the potential treatments of fragile-X syndrome.