The gene for cblC had been discovered by researchers who studied several hundred patients with similar symptoms. A few of those patients, however, did not have the genetic mutation that that was common to the cblC patients. And some, like Max, had symptoms that didn’t quite match up.
“We knew from early on that something was unusual about this patient,” says Johan Van Hove, MD, a CU professor in the Department of Pediatrics, who saw Max when the boy was just a few months old.
Max was labeled as having cblC – but Van Hove and others on a team of metabolism experts at Children’s Hospital Colorado had their doubts. Some of Max’s symptoms seemed too severe for that diagnosis.
So Shaikh, an associate professor in the medical school’s pediatrics department, and CU colleagues, used what is called next generation genetic sequencing to delve into Max’s DNA. They also looked at genes of patients who didn’t fit the cobalamin C model, obtained from partners at the National Institutes of Health, and in Canada and Switzerland.
All of those patients carried mutations that hadn’t been identified before. The problem was due to flaws in a gene designed to control the workings of an enzyme that, in turn, helps the body metabolize B 12. The article gives a name to Max’s disease – cblX -- because the gene is on the X chromosome.
“This discovery will lead to the correct diagnosis of this serious genetic disorder and will change the way that genetic counseling is given in these families,” says study co-author David Rosenblatt, MD, with the Research Institute of the McGill University Health Centre. “It also helps explain how vitamin B 12 functions in the body, even for those without the disorder.”
The research moves matters to a new phase, Van Hove says, because
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