Media playback is unsupported on your device Media caption Many GPs "do not know" about Williams Syndrome, parents say

Children with a rare genetic condition which makes them very friendly can grow up isolated because of a lack of awareness, a Welsh academic has warned.

Youngsters with Williams Syndrome tend to be empathetic, social and endearing, but as adults they often struggle when people do not know how to react.

Prof Phil Reed, of Swansea University, said more support services were needed.

The Welsh Government said £20m had been set aside for those with such conditions.

Williams Syndrome, which was first identified in 1961, affects about 300-400 people in Wales.

"For them the world's a very friendly place and that mismatch between their extreme friendliness and their inability to understand the reactions of people can lead to anxiety, social isolation and loneliness," said Prof Reed, a psychologist.

He believes support is patchy and needs to be improved to reduce the burden on services in years to come.

He added: "If you look into social services support, adult mental health support for these individuals and perhaps their parents, a little bit of money up-front would go a long way to alleviating a lot of problems later."

Image caption Prof Phil Reed of Swansea University says more support is needed for those with Williams Syndrome

What causes Williams Syndrome?

It takes 25,000 genes to make a human, but with Williams Syndrome about 25 genes are randomly deleted from the middle of one chromosome.

"It's not inherited. The only way it's inherited is if you are a person with Williams Syndrome you have a 50% chance of having a child with Williams Syndrome, but if you're not, it could happen to anybody," said Prof Reed.

People with Williams Syndrome can feel anxious over stimuli such as the noise of a vacuum cleaner or the texture of food, but it can also cause heart problems, developmental delays, and learning disabilities.

It has been described as the "opposite of autism" in children.

Media playback is unsupported on your device Media caption The Caerphilly three-year-old living with Williams Syndrome

Harrison Evans, three, from Newbridge, Caerphilly county, was diagnosed with Williams Syndrome when he was a year old.

He loves bouncing on his trampoline, playing with his toy helicopter and going to the supermarket in Pontllanfraith.

His condition means he does not have the typical sleep hormone levels of a child his age, so Harrison wakes up every two hours at night.

His parents, Sarah and Scott, agree that there should be more support.

"It's not fantastic, it's taken us a long time to get the help he needs, it's hard because only one-in-five GPs have ever come across the condition," said Sarah.

"Around three quarters of the appointment is taken up explaining what it is that Harri has," added Scott.

Image caption Angharad Rowlands and her son, Iago, who has Williams Syndrome

Angharad Rowlands lives in Brithdir, near Dolgellau, and her son Iago, three, was born with Williams Syndrome.

She said: "If we had some more resources locally for us, more occupational therapy sessions and physiotherapy sessions, speech and language therapy sessions, an increase in the frequency of them would help Iago immensely."

The Welsh Government said it was overhauling the whole system to help those with conditions like Williams Syndrome.

"We expect health and social service providers to support all people across Wales, regardless of their particular condition or individual needs," a spokesman said.

"We aim to have a society in Wales that doesn't discriminate or stigmatise any individual or group.

"Within the education system we want to improve the aspirations of those who need extra support. Our Additional Learning Needs and Education Tribunal Bill, will, if passed, completely overhaul the system for supporting pupils with additional learning needs (ALN).

"We also recently announced £20 million of planned investment to support ALN learners, part of which is aimed at raising awareness of a range of additional learning needs".