Fumarase deficiency has become increasingly common in the fundamentalist Mormon towns of Hildale and Colorado City / Credit: Ricardo360

In the towns of Hildale and Colorado City on the Arizona-Utah border in the US, they’re struggling with a health crisis caused by a recessive gene.

The problem was first discovered in 1990, by Dr Theodore Tarby who specialised in rare childhood diseases. This was after a woman in the community brought her 10-year-old son to him. 

Dr Tarby recognised the boy’s unusual facial features, such as his low-set ears, widely-spaced eyes, small jaw and a prominent forehead. In addition to this, the boy was severely physically and mentally disabled. 

A urine sample was taken and came back showing that the boy had the extremely rare disease fumarase deficiency, which is an inherited disorder of the metabolism.

Fumarase deficiency happens when a person lacks the enzyme fumarase, which helps drive energy to cells. It has the most severe impact on the brain, which takes up about 20 per cent of the body’s energy. 

Children suffering from the condition are often missing parts of their brain and can’t either sit or stand without support.Their IQ is usually around 25, and their language skills are minimal. 

Back in 1990, Dr Tarby believed that there were only 13 cases of fumarase deficiency in the world, making it a one-in-400 million chance of getting it. 

But there was a twist. It turned out that the 10-year-old’s sister, whom the parents believed was suffering from cerebral palsy also had the rare condition. Together with colleagues from the Barrow Neurological Institute, Dr Tarby had soon diagnosed eight new cases within the same community, in children ranging from toddlers to 12-year-olds.

Most of the patients couldn’t walk or sit up, while they all shared the same facial characteristics. 

The likelihood of having the disease within this small community was over one million times the global average, researchers found. And the reason for this was the gradual inbreeding that had been and still is happening over generations that exercise polygamy. 

“With polygamy, you’re decreasing the overall genetic diversity because a few men are having a disproportionate impact on the next generation,” Mark Stoneking, a geneticist at the Max Planck Institute for Evolutionary Anthropology in Germany told the BBC. “Random genetic mutations become more important”.

It’s now estimated that thousands of people in the 7,700-person community have the gene. 







More on these topics