Oliver Chu from California first person to have the one-off treatment for Hunter syndrome

Doctors are cautiously optimistic about a groundbreaking gene therapy for children affected by a devastating inherited disorder after seeing positive results in the first boy to receive the treatment.

Three-year-old Oliver Chu from California became the first patient to have the therapy nine months ago as part of a clinical trial run by researchers in Manchester. It is too early to call the therapy a success, but doctors are encouraged by his progress so far.