Image copyright Tim Smith Image caption Chris Steel says he is happiest when he is acting, as he "wants to show people what he can do"

"I get so anxious if I want to go out to things. I live with my Mum because I don't want to live on my own. I can't do money. I wish I could."

Chris Steel is 40 years old. He is remarkably friendly and engaging, and is happiest when he is on stage acting in plays such as George Orwell's Animal Farm.

As a child, his caring nature led him to take to the bedside of a victim of the Hillsborough disaster, with such compassion and diligence he was given an award by former UK Prime Minister Margaret Thatcher.

Chris is great to take to parties... but he is too trusting Judy Steel, Chris's mother

But he is unable to go out alone - once, when he did, his openness towards strangers and difficulty in understanding when he is in danger meant he lent his phone to a stranger, who stole it.

He has severe anxiety, and needs constant reassurance from the people around him.

'Reeling people in'

Chris has Williams Syndrome (WS), a rare genetic disorder affecting around one in 18,000 people in Britain. It has often been dubbed the 'opposite of autism'.

People with WS are empathetic, social, friendly and endearing but they tend to have a low IQ, making tasks such as counting money difficult.

They can feel anxious over stimuli such as the buzzing of a bee, or the texture of food.

Williams Syndrome: psychological features Image copyright SPL Attention-seeking behaviour, particularly at parties

Extremely sensitive hearing, to everything from sirens, cars, hoovers, hand-driers, fireworks, to buzzing bees

Attention deficit disorder

Affinity for music

Difficulty with spatial relations, numbers and abstract reasoning

Desire to please and be helpful

Ability to gauge and react to social situations without understanding them

Late to learn to walk, talk and use the toilet

The need for reassurance in some cases can leave children of loving households calling 999 and feigning an emergency, as they crave adult attention so much.

WS, first identified in 1961, can also cause heart problems, developmental delays, and learning disabilities.

For the psychological side of the disorder, acting can play to the strengths of people with WS. Chris says: "I am good at reeling people in and being a character in different things."

He acts with a charity called Mind the Gap, based in Bradford, near his home town of Bingley in West Yorkshire, and cites the time he was a pirate in a play called Treasure Island as amongst his favourites.

Behavioural subtleties

When he was a child, and visiting his father in hospital, Chris met Tony Bland, who was severely brain damaged when he was crushed in the Hillsborough stadium disaster in 1989.

Chris befriended Tony, and stayed, loyally, by his bedside for weeks. "Chris can talk to anyone and doesn't need a response," his mother Judy says.

It can be difficult when you see the surge of funding for the tidal wave of autism Lizzie Hurst, Chief executive, Williams Syndrome Foundation

Judy says he is also "great to take to parties" as he happily introduces himself to new people.

But there is a flip side of this social ease. Judy says Chris is "too trusting", and has been taken advantage of.

She said he also needs people around him to be happy and guide him in what opinions he should have.

People with WS may make prolonged eye-contact, and be over-engaging, which can put them in danger.

Language ahead of mind

There are also further aspects of the disorder which can land them in hot water.

Lizzie Hurst, chief executive at the Williams Syndrome Foundation, says: "People [with the disorder] conduct themselves in a way that makes them extremely vulnerable.

"They don't have the cognitive ability to match their linguistic age.

"There is a classic autistic profile to which Williams Syndrome is the polar opposite. People can gauge the mood of a crowd and adopt without understanding the nuances of the situation."

Image copyright SPL Image caption People with Williams Syndrome can make good party companions, as they are friendly and compassionate

Ms Hurst says there were "questions to be raised" over whether people with WS could be legally responsible for themselves. "I would say they cannot," she adds.

She is working to raise the profile of the disorder amongst GPs, as she says only one in 40 GPs will encounter the disorder and babies with WS can be difficult to identify.

Williams Syndrome: physical features Image copyright SPL High blood calcium levels

Slight facial abnormalities

Low birth weight, or slow weight gain

Feeding problems as babies

Abnormal tooth shape

Kidney problems

Joint problems, low muscle tone and range of motion

Colic or irritability as infants

Hernias

Facial features in young children include a small, upturned nose, long upper lip, wide mouth, full lips, small chin and a white lacy pattern on the eye's iris.

Autism 'tidal wave'

Anxiety can be made worse if the disorder is not diagnosed, she said, as people feel even more isolated.

Ms Hurst's charity does not get any funding from the government, relying on fundraising and donations. She puts on barbecues, Christmas parties and holidays for people with WS and their families.

"I think the government should do more," she says. "It can be difficult when you see the surge of funding for the tidal wave of autism.

"WS people are just as needing as other people with mental disorders and in many ways they are more needing of support and attention, and that all comes at a price."

People with WS do not have a lower life expectancy than other people, and some may go on to get jobs, most often in a voluntary capacity, where their helpful nature can be useful.

Dr Debbie Riby, senior lecturer in the Department of Psychology at Durham University, has been working on the disorder for 12 years.

Anybody can have a child with Williams Syndrome Dr Debbie Riby , Senior lecturer, Durham University

Genetic basis

She says WS occurs when part of chromosome seven is deleted, which happens sporadically.

"Anybody can have a child with Williams Syndrome," she says.

Dr Riby says there is no pre-natal screening, but often doctors can pick up clues if a young child has heart murmurs, and problems putting on weight.

She has been running parent focus groups to understand the anxiety side of WS to come up with practical steps families can take to help themselves keep their children calm and happy.

Dr Riby says: "The work around Williams Syndrome used to focus on the theoretical side. I wanted to focus on the practical side. There is still an awful lot that we can do.

"The most important thing is for us to think about how we can use research to support families."