A July 27, 2017, BBC article explains how fumarase deficiency continues to proliferate among polygamists in Short Creek on the Utah-Arizona border. The community is made up of members of the Fundamentalist Church of Jesus Christ of Latter-Day Saints (FLDS). The sect is not associated with the main body of The Church of Jesus Christ of Latter-day Saints, which forsook polygamy over 100 years ago and excommunicates members who try to practice it.
During the 50 years that Mormons did practice polygamy, there was a constant influx of new converts to the Church, guaranteeing genetic variety, but the sect at Short Creek is a closed community, setting up a dangerous situation for inbreeding of negative genetic traits.
Fumarase deficiency presents symptoms of “unusual facial features, including a prominent forehead, low-set ears, widely spaced eyes and a small jaw” along with very serious physical and mental disabilities. The first case was identified in 1990. At that time, it was so rare that there were only 13 cases known.
Eight more cases were found immediately in the community. There, “the likelihood of being born with fumarase deficiency is over a million times above the global average.”
Faith Bistline has five cousins with the disease, who she used to look after until she left the FLDS in 2011. “They are completely physically and mentally disabled,” she says. The oldest started learning to walk when he was two years old, but stopped after a long bout of seizures. Now that cousin is in his 30s and not even able to crawl.
In the Short Creek polygamist sect, 75% to 80% of citizens are blood relatives of Joseph Jessop and John Barlow, who founded the community. Excess males are banished so females can be polygamous wives, contracting the gene pool. Inbreeding combines recessive genes, so the mutation shows up often in the population. “Today the number of people carrying the fumarase gene in Short Creek is thought to be in the thousands.”