Apple Magazine
Metabolic Clinic Tackles Rare Conditions
Medical team handles about 400 patients with genetic disorders
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MELANIE COLLISON
Apple Magazine
Here are some words you don’t ever want to hear a doctor say about your child: Pompe, Gaucher’s, Fabry, PKU.
They are among the 700 or so “inborn errors of metabolism,” more recently known as “genetic metabolic diseases,” identified and treated at the Calgary Health Region’s Metabolic Disorders Clinic.
Located on the third level of the new Alberta Children’s Hospital, the clinic often sees patients and families who have spent years trying to understand what ails them.
“Parents and patients are relieved to know what it is [they’re dealing with], even if we can’t treat them, because they’ve gone for years searching for the diagnosis. For the ones we can treat, it’s life-saving,” says Dr. Robin Casey, Director of the Inherited Metabolic Disorders Clinic, Department of Medical Genetics and Pediatrics, Alberta Children's Hospital.
These genetic metabolic diseases are so rare that even though the clinic is located in the children’s hospital, it treats adults as well. There’s neither the demand nor the duplicate medical team for a separate unit.
Close to 400 patients, including pregnant women, come for treatment from southeastern British Columbia, southern Alberta and southwestern Saskatchewan. Some of the disorders the clinic treats can be rendered innocuous if they’re diagnosed before symptoms appear. Alberta’s newborn metabolic screening program currently tests for phenylketonuria (PKU), congenital hypothyroidism and biotinidase deficiency, which can be readily treated with a lifelong regimen of protein substitute, thyroid medication and vitamin B respectively. This August, Public Health will add blood tests for another 14 conditions, in keeping with national trends.
Often the first clue parents have that they both carry recessive genes for a genetic metabolic disease is having a child who develops the symptoms. “Parents may decide not to have more children, or may decide to have testing done during pregnancy,” Dr. Casey says.
Advances in understanding many of these diseases, and in technology and drugs, have allowed many people to overcome once-fatal diseases and advance into adulthood with some quality of life. Tube-feeding through the night, for instance, affords some sleep for both the parents of, and children born with, glycogen storage disease. The children no longer have to be wakened to eat every two hours.
More than 20 genetic metabolic diseases can be treated effectively through medical food-replacement formulas, restricted diet and close monitoring by a dietitian with specialized training. The key to preventing the damage of PKU, known as maple syrup disease, for instance, is replacing all meat and dairy and most grains with a protein formula which eliminates the single offending amino acid.
“The diets are restrictive and artificial,” says clinical dietitian Melanie Reeves. “We can’t just eliminate essential things (such as protein), but we need to control them. We need to make sure we’re not over-restricting them, so we do lab work as well as monitoring growth and weight gain to make sure we’re getting the right balance.”
Because babies’ brains develop so rapidly, “for infants, we have to do blood work weekly,” Reeves says. “It’s not as critical when they’re a little bit older, say 10 years old, because their brain isn’t growing and changing as much, so we can reduce it to monitoring monthly.”
These formulas taste bad, so compliance can fall off in adolescence, but alternatives developed in recent years at least offer some variety, Reeves says. “Most of the conditions are picked up very early on, so what the (children) grow up learning is normal for them. Their families, and we as a clinic, drill it into them and encourage them to stick with it.”
For other conditions, research in biochemistry has led to life-saving breakthroughs, such as the development of synthetic essential enzymes which can be administered intravenously. Without those enzymes, the person either cannot metabolize essential nutrients, or accumulates excessive amounts of waste products in organs, muscles or blood vessel walls, causing terrible damage.
“Each individual needs unique treatment,” Dr. Casey says. The clinic works closely with pharmaceutical experts, and bone marrow, stem cell and organ transplant experts. Advances in transplant techniques and associated drugs have made a transplant less onerous for some than continuing on the established drugs would be.
“Our goal is to promote a good life for as long as possible and prevent our patients being mentally or physically handicapped,” Dr. Casey says. “We support families as well as patients.”
There are now people with PKU who are nearing their 50s without brain damage because they’ve always been on a special diet. Infants born with Pompe Disease since the development of Myozyme have survived to five or six years of age because they started on the recombinant DNA drug therapy before they were three months old.
Dr. Casey and his colleagues have developed one of five biochemical geneticist training programs available in Canada, accredited under the Canadian College of Medical Geneticists. Pediatricians, medical geneticists and internists are eligible to take the program.
