Surprise autism gender disparity

A ‘protective factor’ may explain how some girls at risk remain unaffected

CHICAGO: Think autism and an image of an awkward boy typically emerges, but the way autism strikes girls, or does not, may help reveal some of the developmental disorder’s frustrating secrets.

Autism is at least four times more common in boys, but scientists taking a closer look are finding some gender-based surprises: Many girls with autism have social skills that can mask the condition. And some girls do not show symptoms of autism even when they have the same genetic mutations seen in boys with the condition.

“Autism may not be the same thing in boys and girls,” said Kevin Pelphrey, an autism researcher at George Washington University.

The causes of autism are not known. Genetic mutations are thought to play a role and outside factors, including older parents and premature birth. But the gender effect is now a hot topic in autism research and one that could lead to new ways of diagnosing and treating a condition that affects at least one in 68 US children.

Brain imaging suggests there may be an additional explanation for why many girls with autism have more subtle symptoms than boys, Pelphrey said. Even in girls who clearly have autism, he said, brain regions involved in social behaviour that are normally affected are less severely impaired.

Also, recent studies on autism-linked genes have found that girls can have the same kinds of genetic mutations seen in boys with autism, but not show symptoms.

They “even need to have twice as many mutations on average to actually manifest with autism”, said Joseph Buxbaum, director of an autism centre at the School of Medicine at Mount Sinai, New York.

He is among researchers trying to identify a “protective factor” that may explain how some girls at genetic risk remain unaffected, perhaps a protein or other biological marker that could be turned into a drug or other therapy to treat or even prevent autism.

That possibility is likely a long way off, but Pelphrey said this line of research prompted excitement among autism scientists.

Buxbaum is involved in the Autism Sisters Project, which is seeking to enrol hundreds of families with autistic sons, but unaffected daughters.

Girls and their families visit the New York lab to give saliva samples for DNA analysis and efforts are under way to expand.

Evee Bak, 15, hopes her samples will eventually benefit her older brother Tommy. The suburban Philadelphia siblings are just a year apart. They play in a garage band – Evee on drums, Tommy on guitar and vocals. He’s a masterful musician, but has trouble reading social cues.

Autism is diagnosed by observing behaviour, there’s no blood test for it. Some experts say genderbased differences highlight a need to develop different ways to evaluate boys and girls.

Autism screening, recommended for kids starting at 18 months, uses tools based on research in autistic boys, said Rachel Loftin, clinical director of an autism centre at Rush University Medical Centre in Chicago.

One widely used screening questionnaire for parents includes questions like “Does your child play make-believe, make eye contact, seek praise, show interest in other children?”

Girls with autism, especially mild cases, often don’t show obvious problems in those categories; they’re more likely than affected boys to play pretend with toys rather than lining them up by size or shape.

Government data show that all forms of autism, mild to severe, are more common in boys and that the average age at diagnosis is four.

But Loftin said anecdotal evidence suggests a two-year lag time in diagnosis for girls, especially those with mild cases. And she suspects many cases are missed or misdiagnosed.

That means a delay in early intensive behaviour therapy that is the main treatment for autism.

Some girls manage to camouflage symptoms until pressure to fit in at school become overwhelming, delaying diagnosis until around age eight or nine, said Alycia Halladay, chief science officer at the Autism Science Foundation, a non-profit educational and research-funding group, which is paying for the Sisters Project. The prominent autism advocate, professor and author Temple Grandin, wasn’t fully verbal until age four.

“It was obvious something was drastically wrong with me,” Grandin said. But she said she learnt to adapt, in part because with “1950s parenting” she was faced with intense encouragement to develop.