Fragile X syndrome study to reveal more

By Dr. Ananya Mandal, MDJul 25 2011

Fragile X syndrome is the most common inherited cause of intellectual disability in the world. Medical experts, including the Mater Hospital's Dr Helen Heussler, are today launching a new push to uncover the secrets of a disorder that affects a child born in Australia every week. Fragile X is passed from parent carriers who often exhibit very few symptoms. Estimates suggest more than 100,000 Australians either carry the gene mutation that causes Fragile X or have the syndrome, yet the vast majority have not been diagnosed, according to the Fragile X Association of Australia.

The symptoms of the condition can include severe intellectual disability, developmental delay, poor coordination, behavioral problems, delayed and repetitive speech, and autistic behaviors. It can also cause a range of physical problems, including a long narrow face, large and prominent ears and enlarged testes, flat feet, puffy eyelids, low muscle tone, gastrointestinal problems, hernias, ear infections, squint and a hollow chest. Nearly 30 per cent of all people with Fragile X also have autism. Some women carriers can have fertility problems in their late 20s or early 30s and experience an early menopause.

Scientists from the University of NSW and Victoria's Monash University are leading the study into late-onset Fragile X. The Australian study aims to look at why carriers suddenly show such symptoms as they approach middle age despite having no issues previously. The study will focus on late-onset FXS (Fragile X syndrome) and FXTAS (Fragile X Tremor Ataxia Syndrome) and involve a series of tests in men aged over 40 to examine their balance and memory skills.

“While we have known for some time that carriers pass the gene on to their children and future generations, resulting in FXS, little is known about the effects of the Fragile X gene in some carriers,” said associate professor Julian Trollor, head of the UNSW's department of developmental disability neuropsychiatry. “Some older, female carriers may experience ovarian insufficiencies, which can cause irregular menstrual cycles, infertility and early menopause. Older, male carriers may develop Fragile X Tremor Ataxia Syndrome (FXTAS), which is a condition affecting balance, tremor and memory loss and is often misdiagnosed as Parkinson's or dementia. The devastating reality of FX is that little is known about the mutation and why only some carriers are affected and not others,” he added.

Monash University's developmental neuroscience and genetics disorder lab director Prof Kim Cornish said the researchers would be trying to identify any common links among the men which indicate they might be prone to FXTAS. “Prior to this research it was assumed if you were a carrier you were symptom-free…But what this research has found so far is that in some cases there is an early profile in problems and memory and inhibition. What we have found is that some males who have that profile quite early in their 30s and 40s may go on to develop tremors (FXTAS),” she said. There is no cure for FXS and the only way to diagnose the condition is through genetic testing.