Elena Lopez-Rangel

MSc, FRCPC, MD

Investigator, BC Children's Hospital

Fragile X syndrome (FXS) is the most common cause of inherited mental retardation with a worldwide prevalence of 1/4000 in males and of 1/8000 in females. Individuals with FXS exhibit a range of emotional and neurocognitive features including intellectual disability hyperactivity and attention problems, executive function deficits, hyperreactivity to stimuli, anxiety and mood instability, and ASDs. Fragile X syndrome is caused by a mutation int eh FMR1 gene leading to a deficit in FMR1 gene protein (FMRP). In general, the severity of the FXS physical phenotype and intellectual impairment is correlated with the magnitude of the FMRP deficit.

At this time, there is no specific treatment for FXS and clinical practice varies. The most common medications used to treat the FXS symptoms are stimulants (i.e. methylphenidate), selective serotonin reuptake inhibitors (SSRIs), alphaadrenoreceptor agonists, mood stabilizers, and antipsychotic medication. The use of any of these drugs is compromised by their limited efficacy and safety profile.

In recent years, there has been a new understanding of the neurobiology of FXS that involves the metabotropic glutamate receptor (mGluR). Based on the location and on the activity of mGluR in the central nervous system, there is a plausible relation between many of the phenotypic features in FXS and the deregulation of fragile X mental retardation protein (FMRP) activation. If this hypothesis is correct, mGluR antagonists should be a novel pharmacological approach to normalize the deficits caused by the lack of FMRP.