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Called actinic prurigo, the disease is usually seen in small pockets of American Indians, and has been reported in Saskatchewan, Manitoba, the central United States and Columbia. The disease is linked with exposure to the sun.
A research team centred in the Department of Medicine has found that people with the disease have a genetic predisposition to it. Dr. David Sheridan, a member of the team, said this indicates that it likely has been in the western hemisphere for centuries, and was not introduced by Europeans.
"The cause appears to be neither infectious nor environmental. It tends to run in families but no according to any clearly defined genetic pattern," Dr. Sheridan said.
People who have it develop a rash on any part of their body that is exposed to the sun.
"The severity varies from one person to another. In some, the pain and blistering are so bad they do not go outside when the sun is shining." "It results in a real nasty skin rash on sun exposes skin."
According to Dr. Sheridan there is no treatment for this disease and people who suffer from it should shield themselves from the sun. "A good high grade sunscreen rated about 20 or higher should be applied to areas exposed to the sun", he stated.
"It has not yet been established whether actinic prurigo should be considered a distinct skin disease or a unique form of polymorphous light eruption".
The genetic predisposition to the disease (genetic marker) was established through a process called human lymphocyte antigen (HLA) typing. This involves determining the types of proteins (antigens) on the surface of white blood cells. The researchers found significant differences when they HLA typed a group of people with the disease and a control group without it. Two specific antigens showed up significantly more often, and another significantly less often, in the actinic prurigo patients than in the controls.
The participants, 32 patients and a similar number of controls, were of Cree ancestry. All but two were from northern or central Saskatchewan and most lived in the La Ronge area, which contains one of the North American pockets of the disease. For comparison, a control group of whites was also HLA typed.