A desperate father has launched a fundraising bid to treat his son after he was diagnosed with a debilitating central nervous system disease.

Tiago Gouveia was diagnosed with Spinal Cerebellar Ataxia Type Seven (SCA7) after chickenpox triggered the genetic condition, inherited from father Marvino.

The four-year-old can no longer walk unaided and his weight has dropped to just 1.7 stones - 11kg - since last May - half of what he should normally weigh for his age.

He has also developed kidney disease as a result of his illness and could go blind, lose his ability to speak and no longer be able to swallow if not treated.

Dad Marvino, 40, who lives in Malvern Road, Orpington, is now hoping to raise £30,000 to fund stem cell treatment in Bangkok, Thailand, which could cure Tiago.

He said: "He was born well, and he was a normal child growing up until the age of two-and-a-half.

"In May 2015, he was with his cousin who had chickenpox, and it triggered the disease.

"It's a genetic condition, and I carry the gene - my mum, sister and niece all have it.

"After six to seven months, Tiago stopped walking and got a lot more wobbly before it came to a point where he couldn't walk anymore.

"He's lost lots of weight and for now his sight is okay, but it will get worse.

"He was vomiting every day until he got a gastrostomy on April 4, and we're hoping that will stop it - he had been fed through a tube since November but it was making him sick.

"He developed nephrosis, which affects his kidneys, so now he's on steroids as well as seven or eight other types of medication.

"It came to the point where we said we can't wait to fix him, so we decided to start the fundraising page for stem cell treatment."

Tiago has inherited the condition from finance worker Marvino, whose mother, sister and niece also have the genetic disorder.

His Geneva-based sister Canisia Brunier, 52, her daughter Melissa, 21, and Marvino's mother Latifa Goveia, 71, who lives in his native Portugal, all suffer from SCA7.

Marvino added: "He's got a bad gene, and because he's young and male the disease is developing much more quickly.

"He weighs 11kg and he should be double that, he's very skinny and you can see all his bones.

"Sometimes he's in a good mood but the medication gives him really bad moods.

"I don't have words to describe it, it's just too much."

Marvino and full-time carer wife Rosa Gouveia, 38, are also parents to Andre, 11, who does not have SCA7.

The family are now hoping to raise enough money for Tiago to undertake crucial stem cell treatment.

They have already raised £7,200 on JustGiving but need more.

Marvino said: "We're hoping we can get this money to help him, it's been very tough seeing him suffer like this - he's always sick.

"The stem cell treatment could help a lot or maybe even cure him and the doctor says he has a very good chance of improving.

"He's getting worse every day so need to do it soon.

"We've had a lot of support from our friends and family and we're really happy with how much we've raised, but we're still trying to spread the word."

The fundraising page is here