The following information regarding PKU was provided by The Canadian PKU and Allied Disorders and can be found at their website here 


Phenylketonuria - PKU

PKU is short for phenylketonuria (pronounced fen'-il-kee'-to-nu'-ria)

PKU is a rare, inherited metabolic disease that results in mental retardation and other neurological problems when treatment is not started within the first few weeks of life.

How can PKU affect a person?

People with PKU are missing an enzyme to break down protein in food, specifically one aminio acid. This amino acid is called phenylalanine, often called PHE (pronounced fee)
Since this amino acid cannot be completely processed, it builds up in the blood and excess amounts cross the blood-brain barrier. When excess amounts build up, brain damage and other neurological problems result.

Most children and adults with PKU must follow a special diet. The PKU diet involves strictly controlling the intake of natural protein (which contains phenylalanine), drinking a synthetic phenylalanine-free protein formula (known as medical food) and eating special low-protein food. The synthetic formula and special low-protein foods are expensive.

How often are children with PKU born?

PKU is inherited as an autosomal recessive trait. In other words, two people who conceive a child must both be carriers of the gene in order for there to be a chance that their infant will have PKU. When two carriers conceive a child, there is a one in four or 25% chance for each pregnancy that the baby will have PKU.

It is estimated that PKU occurs with a frequency of one in 12,000 newborns in North America. This amounts for about 300 new cases each year.
The incidence varies in other parts of the world, it occurs with a frequency of 1 in 4,500 new born babies in Ireland and Turkey, 1 in 10,000 in most of Europe, and 1 in 11,000 in South America.

Is it possible to prevent the symptoms?

YES, fortunately, if the child is diagnosed early (between 7 and 10 days after birth) and treatment is started right away mental retardation can be prevented. There is a screening program for PKU available for Canadian children, which takes place shortly after birth (newborn screening). All children with PKU have access to treatment. To maintain proper health and development the blood PHE level must be kept in good control throughout the child's life.

How is PKU treated?

  • Reduce phenylalanine intake through low PHE diet
  • Provide necessary alternative to natural protein through œmedical formula 
  • Periodic monitoring of blood PHE levels


How is the PKU Diet?

The diet for the most severe form of PKU eliminates all of the very high protein foods since all protein contains phenylalanine. This means that all concentrated sources of protein must be eliminated from the diet in order to limit the amount of phenylalanine. The diet does not allow consumption of meat, fish, poultry, milk, eggs, cheese, ice cream, legumes, nuts, or many products containing regular flour.

A synthetic formula is used as a nutritional substitute for the eliminated foods. This formula is very expensive.
The diet is supplemented with special low protein foods and weighed or measured amounts of fruits, vegetables and some grain products. These foods are allowed in quantities that suit the individual child's tolerance for phenylalanine.

How is PKU diagnosed?

Every baby born in Canada is supposed to be tested for signs of elevated phenylalanine. This effects about one baby in 12,000 in Canada. The reason for this universal newborn screening for PKU is that a baby with PKU does not show signs or symptoms until after irreversible harm has occurred. The lack of early signs and symptoms means the best mother and father working with the best doctors and nurses do not have a good chance of preventing permanent brain damage. That why we call newborn screening a modern miracle.

Most Canadian babies have been screened for PKU since the 1960s. We do not screen children born in other countries when their families move to Canada.


What's New in PKU Treatment & Management?

KUVAN - Tetrahydrobiopterin (BH4)

Kuvan: On April 30, 2010, Health Canada issued a Notice of Compliance to BioMarin Pharmaceutical Inc. for the drug product, Kuvan.


Kuvan is a pharmaceutical formulation of BH4, the co-factor for the enzyme phenylalanine hydroxylase (PAH). PAH hydroxylates Phe through an oxidative reaction to form tyrosine. In patients with PKU, PAH activity is absent or deficient. Treatment with BH4 can activate residual PAH enzyme, improve the oxidative metabolism of Phe, and decrease Phe levels in some patients.  You need to talk to your clinician to see if Kuvan is right for you or your child.  The only way to find out if you or your child is a responder to Kuvan is by trying Kuvan.


Some patients respond to Kuvan with a phe reduction, others experience a phe tolerance increase (with a reduction in the amount of medical foods needed) and some experience neuro-cognitive improvements.  Everyone is different.


Over 100 patients to date in Canada have been tested for response on Kuvan and BioMarin is actively seeking provincial reimbursement for Kuvan.  In the US, over 3000 patients have been exposed to Kuvan. BioMarin is also conducting several clinical trials in Canada with Kuvan.  The Effect of Kuvan on Neurocognitive Function, Blood Phenylalanine Level, Safety, and Pharmacokinetics in Children with PKU (PKU-015) is a seven year study designed to evaluate the long term efficacy of Kuvan in preserving neurocognitive function in children with PKU when treatment is initiated at 0-6 years.  The PKU-015 study still has a few open spots in the ages 2-4 category.  The Safety and Therapeutic Effects of Sapropterin Dihydrochloride on Neuropsychiatric Symptoms in Phenylketonuria (PKU) Patients (PKU-016 trial) is designed to evaluate the therapeutic effects of Kuvan on the symptoms of ADHD and on global function compared to placebo, in subjects with a blood Phe level reduction after treatment, in patients aged 8 years and older.  If your centre is not a clinical trial site or you are not eligible for the trials, you might consider the Kuvan Assistance Program. 

BioMarin Pharmaceutical (Canada) Inc. is committed to help Canadian Patients obtain access to Kuvan.  The Kuvan Assistance Program (KAP) has been established to meet the needs of Canadian patients and health care professionals in optimizing access to Kuvan.  The program is sponsored by BioMarin Pharmaceutical (Canada) Inc. and managed through a partner, Innomar Strategies Inc., which provides services offered by the program.

KAP is a private, confidential, and free patient support service for Kuvan patients and their families, caregivers, or health care professionals.  It offers assistance with drug plan coverage and reimbursement, enrolment in a Starter Program (a free 30-day starter supply of Kuvan), support in managing Kuvan treatment, and further information on PKU and Kuvan.


Patients must sign a consent form agreeing to be enrolled in the Kuvan Assistance Program.  The doctor will complete the form and fax it off.

Once the Kuvan Assistance Program receives the completed Enrolment Form, the Nurse Case Manager will work with the health insurance plan to submit all required paperwork. The Kuvan Assistance Program will provide updates as the process moves forward.  To contact the Kuvan Assistance Program, call toll free: 1-877-597-6744, Monday through Friday, 8AM to 8PM EST.



PEG-PAL (PEGylated recombinant phenylalanine ammonia lyase or ‘PAL’) is an investigational enzyme substitution therapy for the treatment of phenylketonuria (PKU), an inherited metabolic disease caused by a deficiency of the enzyme phenylalanine hydroxylase (PAH).

PEG-PAL is being developed as a potential to treat patients whose blood Phe levels are not adequately controlled by Kuvan. Several centres in the US are participating in clinical trials but there are no sites in Canada. Merck-Serono has the rights to Peg-Pal in Canada but may not bring it here if there is a risk it will not be provincially funded.


Preliminary work with gene therapies in animal models is experimental.


Home Phe Monitor

BioMarin has discontinued work on this project due to ongoing issues with accuracy at the low levels.

The much anticipated Home Phe Monitor (HPM) is being developed by BioMarin as a tool to help manage PKU. The HPM will allow patients to test their Blood-Phe level at any time of day, with just one drop of blood, and they will have the result within a few minutes! It is a very exciting development that many are eager to try.