Her father recalled that when she was seven years old, there were frequent angry spats between the girl and her mother, and he had to step in.

“When Ka-man started school, she could not write or even hold a pen properly, and her mother often scolded her,” he said.

Her brother, one year younger, learned much faster and it infuriated Ka-man when her mother appeared to favour the boy.

“Eventually, Ka-man hated listening to her mum and would scream whenever her mum spoke to her,” Chan said.

It took him three years to fix the relationship. He had to persuade his wife to scold the girl less, to avoid provoking her.

The turning point came when his wife fell ill. “I told Ka-man that her mum loved her and if she kept herself away, mum would be sad,” Chan recalled.

Although the girl had some behavioural issues – she would subconsciously shake her head, blink at a high frequency and her lips would tremble – her autism went undetected through school and into early adulthood.

It was only after she dropped out of her higher diploma programme that she underwent checks that revealed the condition.

Clinical psychologist Rhonda Poon Wing-tak said it was rare for a person with autism to be diagnosed so late.

“A child as young as two years old can be diagnosed,” she said.

Poon said there could be various reasons for a late diagnosis.

“Some patients may not display very obvious symptoms, and some parents are simply not aware that their children might be autistic,” she said. “The earlier a person with autism is diagnosed, the better.”

Without early care and training, a person with autism could face challenges in social interaction, self-care and solving problems, she said.

After her diagnosis, Ka-man was advised to exercise more, and her father took her running in parks.

Chan said that at first, she would be panting after running for just 10 minutes. But he kept up their runs and with his training, she has completed two 10km races in the Standard Chartered Hong Kong Marathon.

Finding a job was hard after she dropped out of her higher diploma course.

At her first job as a receptionist in a toy store, she said her colleagues and bosses teased her and called her “autistic girl”.

Chan helped to calm her down by reassuring her that they were not discriminating against her.

She has done better at her current job.

Chan was proud that she contributed HK$6,000 (US$766) a month towards the family expenses, and happy that she even gave her mother HK$500 to attend morning tea gatherings with her friends.

“They are in a good relationship now and talk to each other every night after Ka-man gets off from work,” he said.

A 2018 survey by rehabilitation organisation Heep Hong Society found that nearly one in two autistic adults in Hong Kong were never employed, and more than two-thirds of employers knew little about autism.

“The situation has improved a lot since 2018, and many employers have called to ask if we have any clients open to work,” said Alan Tam Tsz-hong, manager of the organisation’s Star Light Centre, which helps people with autism aged 15 or above.

“The Hong Kong workplace is more inclusive now, but the mindset of frontline workers should also change. They should understand it is not weird to work with an autistic colleague,” he added.

According to a government survey in 2020, Hong Kong had 22,400 people with autism or 0.3 per cent of the population.

But Tam felt that was an underestimation. “After referring to data in other countries, we estimate the autistic population in Hong Kong to be around 100,000,” he said.