A small gene therapy trial involving several Canadian patients is offering new hope to people living with hemophilia, a rare and potentially fatal genetic disorder.

Hemophilia patients can suffer prolonged or uncontrollable bleeding, even after minor injuries. That's because they lack blood clotting factors, or proteins.

There are two types of hemophilia, A and B, and both are very rare disorders. Hemophilia A affects an estimated 2,500 Canadians, while hemophilia B affects about 600 Canadians, according to the Canadian Hemophilia Society.

A new gene therapy developed at the Children's Hospital in Philadelphia has produced very encouraging results. Preliminary research suggests that a single dose of the experimental therapy may help patients with hemophilia B, which involves a deficiency of blood clotting factor IX.

The therapy involves using a gene engineered to replace the faulty one in people with hemophilia. The engineered gene is placed into an inactivated virus and then infused into the liver, where it helps the body produce a clotting factor that prevents bleeding.

"It poses the possibility for a one-time treatment that would be…potentially life-altering for the patient," Dr. Lindsey George, a hematologist at The Children's Hospital of Philadelphia, told CTV News.

Scientists found that after just one dose, none of the nine patients involved in the trial suffered any bleeding for up to a year. Although more research and larger studies are needed to confirm the benefits of the therapy, researchers are very encouraged.

"It is very exciting, certainly from my standpoint as a clinical investigator," Dr. George said.

Dr. Jerry Teitel, the medical director of the Hemophilia Treatment Centre at St. Michael's Hospital in Toronto, who collaborated with the Philadelphia researchers, called it "a revolutionary therapy."

The results so far are wonderful, in fact even better than what we had dared to hope," he said.

Of the nine patients who've received the treatment, four are Canadian.

Among them is John Konduros, a 52-year-old bakery owner in Cambridge, Ont. As a lifelong hemophiliac, he has always lived in fear of any bumps, cuts or bruises that could cause internal bleeding, disability -- and even death.

"It has probably affected every single part of my life, from being a kid to now," he told CTV News. "If you ever saw me as a kid, I was never in a group. I was always on the sides."

Konduros said it was common for him to miss two or three weeks of school if another kid happened to kick him in the leg while they were playing. In one class photo, he is seen with a big bruise under his right eye - another side effect of his condition.

But since Konduros received the experimental treatment about eight months ago, he has not had any dangerous bleeds.

"I'm extremely happy in the sense of massive relief. I feel like I don't have to be as vigilant or worrisome about everything and anything that's going on around me," he said.

So far, the immune systems of two trial patients have reacted to the treatment, but scientists say there were no serious side effects. Konduros has had no problems with the therapy.

"If the doctors wanted me to go down every weekend for more tests to accelerate anything I would say 'sure' because the improvement it gives anyone who has hemophilia is huge," he said.

Dr. Teitel said scientists have "a long way to go" in developing a therapy that can help more hemophilia patients.

"We need to show that in large numbers, the results do hold up," he said. "We need to show that the results last for a long period of time, not necessarily last a lifetime."

With files from CTV's medical specialist Avis Favaro and producer Elizabeth St. Philip