“Across the Arab world today an average of 45 percent of married couples are related, according to Dr. Nadia Sakati, a pediatrician and senior consultant for the genetics research center at King Faisal Specialist Hospital in Riyadh.

In some parts of Saudi Arabia, particularly in the south, where Mrs. Hefthi was raised, the rate of marriage among blood relatives ranges from 55 to 70 percent, among the highest rates in the world, according to the Saudi government.

Widespread inbreeding in Saudi Arabia has produced several genetic disorders, Saudi public health officials said, including the blood diseases of thalassemia, a potentially fatal hemoglobin deficiency, and sickle cell anemia. Spinal muscular atrophy and diabetes are also common, especially in the regions with the longest traditions of marriage between relatives. Dr. Sakati said she had also found links between inbreeding and deafness and muteness.”

http://www.nytimes.com/2003/05/01/world/saudi-arabia-awakes-to-the-perils-of-inbreeding.html