Polygamy fueling Arizonas rate of genetic disorder

“Arizona has about half the world’s population of known fumarase deficiency patients,” said Dr. Theodore Tarby, a pediatric neurologist who has treated many of the children at Arizona clinics under contracts with the state.

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“It exists in a certain percentage of the broader population but once you get a tendency to inbreed you’re inbreeding people who have the gene there, so you markedly increase the risk of developing the condition,” he said.
The community of about 10,000 people, who shun outsiders and are taught to avoid newspapers, television and the Internet, is home to the Fundamentalist Church of Jesus Christ of Latter Day Saints (FLDS), a sect that broke from the mainstream Mormon church 72 years ago over polygamy.

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Local historian Benjamin Bistline said 75 to 80 percent of people in the area are blood relatives of two men — John Y. Barlow and Joseph Smith Jessop — who founded the sect on the remote desert plateau in the early 1930s.
“There aren’t any new people coming in. It’s a closed door and that gene just keeps getting passed around,” said Bruce Wisan, a court-appointed accountant overseeing a trust of the sect’s assets.

Msnbc.msn.com, June 14, 2007

We actually see the same thing with Pakistani immigrants in Norway. A lot of them come from the same rural area in Pakistan, and they have been inbreeding between cousins for quite a while. Traditions are to blame.