When little Sabrena was rescued from a Pakistani orphanage, little did her future parents realise she had an incurable blood disease.

Dumped on a dirty doorstep in a busy street in Karachi, she was one of the country's thousands of forgotten children.

Now the four-year-old is happy and loved at home with her caring parents in Marston, Oxford.

Two years after Sabrena was rescued, her parents Sobia and Amjad Afridi, of Ferry Road, Marston, took her to the doctor because she wasn't putting on weight.

They were told she was suffering from the incurable blood disorder thalassaemia, a condition that prevents the body producing enough haemoglobin, leading to life-threatening anaemia.

Yesterday, the couple used their experience to support this year's Jeans for Genes Day, which encouraged people to pay to wear jeans to work, to raise money for research into genetic disorders.

This year, the campaign is raising cash to fund research into thalassaemia.

Mrs and Mrs Afridi had tried to conceive for 11 years and underwent six IVF cycles before travelling to Pakistan to adopt in 2003.

Mrs Afridi, 40, a project worker at Oxford Brookes University, said: "Sabrena asks me when she will get better and I cannot answer her.

"We were very pleased when we learned that this year, Jeans for Genes was funding an awareness campaign by the UK Thalassaemia Society. It will help parents, many of whom won't have English as their first language, to talk about the condition to teachers and other professionals."

In 2003, when the couple were approved as adopters, they travelled to Karachi.

Mrs Afridi said: "There is a little steel cradle near the front door of the orphanage attached to a string and a bell.

"People ring the bell to let the orphanage staff know they are leaving a child there. I just sat and cried when I saw all the children."

On December 22, they received a phone call to say a baby girl had been abandoned — and 20 minutes later the Afridis were holding their new daughter Sabrena.

Mrs Afridi said: "She is now four and needs monthly blood transfusions and nightly infusions to prevent iron building up in her body, which would cause irreversible damage to her internal organs.

"She will need even more treatments each week as she gets older. But we saved Sabrena's life by bringing her here — she probably would have been dead within two years if she had stayed in Pakistan."

To find out more, or to make a donation, visit www.jeansforgenes.com or call 0800 9800 4800.