TORONTO -- (Canadian Press)--Canadian scientists have discovered the genetic cause for a particular bleeding disorder that traces back to one family in Quebec, and they've developed a genetic test to help diagnose the condition.

Known as Quebec Platelet Disorder, the condition transforms platelets -- blood cells that control bleeding -- from clot formers into clot busters.

Individuals who have QPD are not hemophiliacs, but when they receive a cut, the bleeding can continue for days. An ordinary bruise can become quite large, and joints can become crippled when bleeding seeps into the knees, elbows and ankles, researchers said in a news release Thursday.

In serious cases, blood transfusions are required.

McMaster University hematologist Dr. Catherine Hayward says it's satisfying to know the team of scientists -- from McMaster in Hamilton, Ont., Toronto's Hospital for Sick Children and Universite de Montreal -- has found the genetic cause.

She says QPD is the first bleeding disorder attributed to having an extra copy of a gene, rather than a defective copy.

"QPD is also the first bleeding problem attributed to a mutation in the uPA (urokinase plasminogen activator) gene," says Hayward, a professor at the Michael G. DeGroote School of Medicine at McMaster.

"Now that we know the mutation, we can focus on solving why there is tremendous uPA overproduction in QPD platelets, which will give us fundamental new insights on how the uPA gene is controlled."

The new genetic test is expected to uncover more people with the condition. A baby born recently to a family with a history of QPD had the genetic test to find out if the child would need lifelong monitoring and treatments, the release said.

In some parts of the country, statistics show that about one out of 150,000 persons has QPD.

The Canadian Press, 2010