PARIS, France (AFP) — Scientists have used gene therapy to relieve the symptoms of a teenager suffering from sickle cell disease (SCD) in a world-first breakthrough, they reported on Thursday.

SCD is an inherited disease caused by a gene mutation that results in red blood cells losing their usual donut-like appearance and taking on a sickle or crescent moon shape.

Sufferers — around five million worldwide — often have anaemia and get tired easily, run a higher risk of infections and stroke, and experience bouts of severe body pain.

Many need chronic blood transfusions.

But a team from the AP-HP university hospital group in Paris, the Imagine Institute of Genetic Diseases and gene therapy company bluebird bio said they managed to get a teenager off transfusions.

The boy was the first person to be treated, in Paris in October 2014, for sickle cell disease in a clinical trial with gene therapy. Others have been tested since, but no official results published.

The team collected so-called haematopoietic stem cells, which give rise to red blood cells, from the bone marrow of the youngster, then aged 13.

The immature cells were treated with a therapeutic gene, carried in a deactivated virus, which recoded their DNA to correct blood cell production.

The treated cells were then reinjected into the boy’s body.

Thursday’s results, published in the

New England Journal of Medicine, report on the child’s health 15 months after treatment.

He was still doing well after this point, but an official, updated status has yet to be published in a peer-reviewed journal.

“He is well, he no longer needs monthly (blood) transfusions, anti-pain medication, or hospitalisation,” study leader Marina Cavazzana told

AFP.

SCD is common in Africa, where up to 40 per cent of a country’s population can carry the mutated gene, though most never get sick.

Last month, French researchers reported progress in developing a rapid, on-the-spot diagnosis for the disease.

Early results from a trial in Togo, Mali and the Democratic Republic of Congo suggested the Sickle Scan was a faster, cheaper blood test than existing ones relying on lab equipment, its makers said.

Rapid diagnosis is crucial to start SCD sufferers, especially young children, on potentially life-saving treatment.