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UREA CYCLE DISORDERS

Hello, my name is Michaela Garstin and I'm the Chair for UCDs. 

We found out our daughter has Citrullinemia (a type of UCD) through newborn screening when she  was a week old. She's six years old now and has been on a low-protein diet her whole life.

I like to say that she's my litte chef because she loves cooking and trying all kinds of new low-protein food. You can often find us trying a new recipe at home or dining at a restaurant, carefully watching her protein intake of course!

I'm looking forward to helping fellow Canadians in the UCD community. Please feel free to reach out to me at ucds@canpku.org. 

Join our UCD Facebook group to connect with other Canadian families!

What is a UCD? 
A urea cycle disorder, or UCD, is a genetic disorder that a child is born with. The child inherits a defective gene(s) from their parents. People can be diagnosed with a UCD at any point in their life.

When food that has protein in it enters the body, it’s broken down in the digestive tract. In a person with a healthy urea cycle in their liver, toxic ammonia is turned into urea so the body can get rid of it naturally. 

When a person has a UCD, the urea cycle can’t change the ammonia into urea as well as it should. Ammonia builds up in the blood, and can travel to the brain, because the body can’t get rid of it.Image from Horizon Therapeutics 

Metabolic stressors – viruses, high protein intake, excessive exercise or dieting, surgery or a drug (valproic acid, prednisone or other corticosteroid) – can create excessive ammonia, resulting in severe neurological symptoms. 

Types of UCDs
The name of the UCD is based on which enzyme or transporter isn’t working properly in the urea cycle:

  • OTC – Ornithine transcarbamylase deficiency
  • CPS1 – Carbamoyl phosphate synthetase 1 deficiency
  • Citrullinemia Type 1 – Argininosuccinate synthetase deficiency
  • ASA – Argininosuccinate lyase deficiency
  • ARG – Arginase-1 deficiency
  • NAGS – N-acetylglutamate synthase deficiency
  • HHH – Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome
  • Citrullinemia Type 2 – Citrulline deficiency

Learn more about OTC – meet Kate Vinokurov

UCDs are genetic 
UCDs happen when one or both parents pass down a defective gene that doesn’t work properly in their child. Rarely, a UCD is caused by a random mutation.

OTC is the most common type of UCD. It is x-linked, which means the gene is typically passed down from a mother to her child. Unfortunately, this condition is not included in newborn screening testing in Canada.

The other UCDs are autosomal recessive, which means that two parents, who are both carriers, pass down the gene to their child.

Symptoms  
UCDs affect everyone differently, including the severity. Some people have never had high ammonia thanks to being diagnosed through newborn screening, while others have had multiple high ammonia episodes and require medication – and everything in between.

Common symptoms of high ammonia levels include: