The polygamous town facing genetic disaster

“We are to gird up our loins and fulfil this, just as we would any other duty…” said Brigham Young, who led the Church of Jesus Christ of Latter-day Saints (LDS), or Mormons, back in the mid-19th century. It was a sweltering summer’s day in Provo City, Utah and as he spoke, high winds swirled dust around him.

The holy task Young was speaking of was, of course, polygyny. He was a passionate believer in the practice, which he announced as the official line of the church a few years earlier. Now he was set to work reassuring his flock that marrying multiple women was the right thing to do.

He liked to lead by example. Though Young began his adult life as a devoted spouse to a single wife, by the time he died his family had swelled to 55 wives and 59 children.

Fast-forward to 1990, a century after polygyny was abandoned, and the upshot was only just beginning to emerge. In an office several hundred miles from where Young gave his speech, a 10-year-old boy was presented to Theodore Tarby, a doctor specialising in rare childhood diseases.

The boy had unusual facial features, including a prominent forehead, low-set ears, widely spaced eyes and a small jaw. He was also severely physically and mentally disabled.

After performing all the usual tests, Tarby was stumped. He had never seen a case like it. Eventually he sent a urine sample to a lab that specialises in detecting rare diseases. They diagnosed “fumarase deficiency”, an inherited disorder of the metabolism. With just 13 cases known to medical science (translating into odds of one in 400 million), it was rare indeed. It looked like a case of plain bad luck.

But there was a twist. It turned out his sister, whom the couple believed was suffering from cerebral palsy, had it too. In fact, together with colleagues from the Barrow Neurological Institute, soon Tarby had diagnosed a total of eight new cases, in children ranging from 20 months to 12 years old.

In every case, the child had the same distinctive facial features, the same delayed development – most couldn’t sit up, let alone walk – and, crucially, they were from the same region on the Arizona-Utah border, known as Short Creek.

Even more intriguingly, this region is polygynous. In this small, isolated community of Fundamentalist Mormons (FLDS), the likelihood of being born with fumarase deficiency is over a million times above the global average.

“When I moved to Arizona that’s when I realised that my colleagues here were probably the most familiar I’d ever met with this disease,” says Vinodh Narayanan, a neurologist at the Translational Genomics Research Institute, Arizona, who has treated several patients with fumarase deficiency.

Read more at BBC.