Oliver Moody, 12, has started the treatment designed to treat the genetic disorder mucopolysaccharidosis (MPS) VI. He is one of only a handful of people in the country to receive the therapy, which uses enzymes derived from the rodents.

His father, Paul, 48, from Leeds, said: "Prior to this drug becoming available, Oliver's illness was completely incurable, he had no future. Now something has come along with the potential to halt the effects.

"This is such a serious illness, we were just getting on with life before. Now he has his life back.

"It does sound bizarre that it comes from hamsters – really sci-fi but it works for us. It really is a miracle."

The proteins are harvested from the genetically modified hamsters and given to the patient through a drip. The treatment costs an estimated £300,000 a year and – because of the expense – had to be approved by the Government itself.

Oliver was diagnosed with MPS VI when he was four. Sufferers carry a defective gene which means they are missing a vital enzyme which breaks down harmful chemicals in the body.

Without it, the toxins starve organs of oxygen. Sufferers usually have severe problems with their bones.

But his determined father and mother, Dawn, 44, found a company in America at the forefront of genetic research, that had discovered the enzyme could be derived from hamsters.

"Nothing could compare to getting this treatment for our son – it's better than winning the lottery," said Mr Moody.