New rare disease discovered in teen brothers at BC Children’s Hospital

Over years of genetic testing, a team of B.C. doctors has discovered a rare new disease in two teen brothers impacting their neurological development.

Gain-of-function MARK4 is a change in MARK4 gene that makes it overactive. That particular gene is critical for brain and nervous system function, explained pediatrician Dr. Stuart Turvey of the BC Children’s Hospital.

“We, as pediatricians, track the developmental milestones of babies — when they sit up, when they talk — and it was recognized that these boys were achieving those milestones more slowly,” he told Global News.

“One of them had issues with epileptic seizures, and then as the boys were moving through school, they weren’t achieving the milestones as quickly as their peers.”

2:20 Researchers at BC Children’s Hospital diagnose young man’s rare disease

Turvey said the children’s clinicians approached the Precision Health Initiative at the BC Children’s Hospital two or three years ago, puzzled by the unknown condition that seemed to be driving their symptoms.

Researchers at the initiative, whose work is now published in the U.S. National Library of Medicine, Science Direct and more, used whole-genome sequencing to discover the overactive MARK4 gene, and were able to contrast it with other, more common MARK4 gene issues. The boys are the only two known patients with gain-of-function MARK4 disease.

“Ultimately, we’ll only know the full spectrum of this condition as more patients are diagnosed,” Turvey said.

“The symptoms that we talk about in terms of neurodevelopmental changes in children are not uncommon … so I anticipate there certainly will be more children with this condition.”

1:09 B.C. clinic diagnoses young man’s rare disease

It’s not the first new disease Turvey and the Precision Health Initiative have uncovered, but he said every time it happens, it’s a warm feeling.

“This is why I do this research,” he said. “It’s hugely gratifying for us to be able to give answers to those families.”

The BC Children’s Hospital estimates that one in 25 British Columbians has a rare disease. There are about 7,000 known rare diseases, with dozens more discovered each year, it adds.

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Sarah Traun of Hope, B.C., said it brought “closure and clarity” when her seven-year-old daughter Rebecca’s mystery condition was uncovered two years ago. The Precision Health Initiative found the genetic mutation impacting Rebecca’s immune system, making her more susceptible to viruses.

Prior to that, like the two brothers, Traun said her daughter was constantly poked and prodded as doctors offered up multiple medical explanations.

“It’s very traumatic. None of them are nice to hear,” she explained. “It’s hard to process this over and over and over again.”

Having a sick child is an “isolating” experience, Traun added. When there’s no diagnosis, it’s hard to find a community of patients to belong to.

Traun said she’s excited and relieved for the boys’ families, who will now have the same closure her family has.

The research into gain-of-function MARK4 was supported by Mining for Miracles and the BC Children’s Hospital Foundation.