A charity is urging GPs to test patients for a genetic condition that is the most common inherited cause of learning disability.

There is a “surprising lack of awareness” around Fragile X, experts said.

Fragile X syndrome is caused by an alteration to a gene on the X chromosome, which disrupts the production of a protein needed for brain development.

About one in 250 women and one in 600 men are carriers of the abnormal gene that causes Fragile X syndrome, according to the Fragile X Society, with female carriers at a higher risk of early menopause.

Women with the gene have a 50% chance of passing on the condition to their children, while an affected man will pass the condition on to daughters, but not sons.

Fragile X syndrome affects about one in 4,000 males and one in 6,000 females, causing a range of developmental issues.

Pete Richardson, managing director of the Fragile X Society, said: “As the most common inherited cause of learning disability, there is a surprising lack of awareness around Fragile X syndrome.

“Carriers of the Fragile X pre-mutation often won’t know they are affected.”

People are more likely to be carriers if they have a family history of Fragile X syndrome – or of intellectual disability, developmental delay or autism of unknown cause – as well as infertility problems associated with elevated follicle-stimulating hormone levels or premature ovarian failure.

Women with ovarian insufficiency also have a 2-15% chance of being a Fragile X carrier.

Mr Richardson added: “When a woman shows signs of premature menopause, being a Fragile X carrier is often the last thing that doctors will investigate.

“We need this to change. Now.”

According to the Fragile X Society, patients who suspect they may carry the gene can ask medical professionals for a Fragile X (FMR1) DNA test.

Alex McQuade, 41, raised concerns when her baby missed his developmental milestones.

She said: “At no point was there a conversation about genetics, despite myself and husband Chris telling doctors that I had a female cousin with what I thought was an autistic son.”

The couple, from Groby, Leicestershire, thought the issues experienced by their son, Evan, now 10, were a one-off.

However, their second child Xander, now seven, had similar problems.

Mrs McQuade said: “I began doing my own research online. I knew it was like autism, but autism didn’t quite fit.

“It wasn’t long before I came across Fragile X syndrome. When I found the list of physical symptoms there was no doubt in my mind that the boys had it.”