A Chinese girl with a rare medical problem has the appearance of a child - despite being 19-years-old.

Zeng Yushan was born in June 1994 in the township of Huzhu in Fushun County in south-western China's Sichuan Province.

As The Daily Mail reports, at seven years old, she stopped growing and was diagnosed with a tumour on her pituitary gland, which caused a deficiency in growth hormones.

The pituitary gland is found behind the bridge of the nose and below the base of the brain, and is about the size of a pea.

It releases hormones growth and puberty hormones, among others, directly into the blood stream.

Tumours on the pituitary gland - though rare - can stop people growing and developing normally, said Ashley Grossman, professor of endocrinology at Oxford University.

He told MailOnline: 'Some say such children may even live longer than expected but that is uncertain.

'But in China, treatment for pituitary problems is not routinely available unless you pay for it. 

'Pituitary patients often don't get the help they need.'

This was the case for Zeng's parents, who couldn't afford to pay for treatment.

They argued bitterly about the disease before finally divorcing, leaving Zeng with her father Yul Wei, 43.

But shortly after the divorce, her father was also diagnosed as being seriously ill.

Unable to pay any of their bills, the pair ended up on the streets begging, travelling from their home to the cities of Zigong, Chengdu and Guiyang.

Instead of going to school, Zeng was used as a child beggar due to her young appearance.

In 2013, Zeng's father died from gastric cancer, leaving her alone.

After she was spotted begging, a warm-hearted couple who had two grown-up daughters of their own, agreed to take her in.

Guo Liu, 50, said that when they first saw her, he and his wife were unsure if she was a boy or girl because she had no hair, and had suffered horrific physical problems because of her medical condition.

She is now getting regular medical care and although she is 20, still looks as if she is seven or eight-years-old and has the mental ability of a child aged around five or six.

Mr Gui said: 'We plan to take her after the Spring Festival to a doctor in the capital Beijing who might be able to help her.

'For the moment she is okay with us, but we want to try and get into a position where she might be able to do something for herself when we are no longer able to look after her.'

Zeng has made it clear she is hugely attached to her new parents.

Her biggest wish is to be able to go to school, even though no schools at the moment will take her because of her real age rather than her apparent age.