When a newborn girl from Baffin Island, Nunavut, was medically evacuated to Ottawa, she received standard formula for premature babies. She developed diarrhea and wasn’t absorbing nutrients properly, which sent doctors hunting for answers.
The diagnosis? Congenital sucrose-isomaltase deficiency or CSID — a rare form of carbohydrate malabsorption caused by an enzyme deficiency.
In Monday’s issue of the Canadian Medical Association Journal, Dr. Matthew Lines of the Children’s Hospital of Eastern Ontario in Ottawa and his co-authors describe how they confirmed the genetic mutation behind the baby’s condition.
They also found the same mutation occurred in about three per cent of healthy Inuit babies living across Canada's High Arctic.
"This is a simple blood test," said Lines. "It makes it easier for us to recognize this potentially treatable condition early."
Until now, doctors diagnosed CSID by taking a biopsy of tissue from the small bowel, which is invasive and technically challenging to do in infants. Feeding sucrose is another diagnostic option, but it leads to abdominal discomfort and diarrhea in patients with the condition.
In adults with CSID, the condition can be subtle and misdiagnosed as irritable bowel syndrome.
"I'm sure there are a lot of people walking around with CSID who may have symptoms and they may not understand why. So I think first of all, can we become better as a community of physicians at recognizing when children need to be on a specific diet for instance," Lines said.
Historically, the Inuit diet was rich in game and fish and relatively low in carbohydrates. With the introduction of baby formula, the problem became recognized in the last 40 years.
The findings should prompt doctors to consider CSID in Inuit children and adults with gastrointestinal symptoms. If there’s a strong clinical suspicion for the condition, the researchers said diet changes shouldn’t be delayed while waiting for genetic results.
The baby who inspired the study likely showed a severe presentation because of her complete lack of active enzymes and long exposure to sucrose in the diet, Lines and his team said.
She was switched to a carb-free formula and was doing well when she was examined at the age of five months.
Researchers at the University of Ottawa, Western University and Robarts Research Institute in London, Ont., and the University of Washington, Seattle, were also part of the study.