Dr. Tarby told Time magazine in 2008 that the community doesn't believe that inbreeding and polygamy is making the issue worse.
"They have their mythology about the condition. They think it's something in the water, or something in the air," he said.
Before he retired, he said he addressed FLDS leaders about measures they could take to stop the spread of the disease.
He said they should bar marriage between two people that have the recessive gene or ask the couple not to have children.
If an already married couple have a child that presents the disease, they should discontinue having children in the future or undergo testing during pregnancy and abort any fetus that tests positive for the gene. The group refused to follow this advice
"It's not something they are willing to do," Tarby said.