Phenylketonuria (PKU)

A rare disorder that prevents the break down of phenylalanine.

aadc dopamine deficiency
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Developmental Delay


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Rare Inherited Disorder

Phenylketonuria (PKU)

Phenylketonuria (PKU) is a rare disorder that prevents the body’s ability to break down an amino acid called phenylalanine (a.k.a. Phe). Without the enzyme needed to control Phe excess levels of this amino acid

Build up in the blood. This can hinder a child’s growing brain, cause mental disabilities and/or behavioral problems, and even lead to brain damage.

Phenylketonuria (PKU) Symptoms
Phenylketonuria (PKU) Symptoms

Phenylketonuria (PKU) Symptoms

The symptoms of PKU range in mild to severe and typically present as some form of mental disability or behavioral problems. These issues often present soon after birth, and when left untreated can lead to serious brain damage.

Other common symptoms can include developmental delay, seizures and autism. Having eczema, as well as lighter coloured hair than other family members have also been shown to be symptoms of PKU.

Phenylketonuria (PKU)


Phenylketonuria (PKU) Diagnosis

Your doctor will ask about your child’s developmental history and give them a physical exam. Symptoms for AADC deficiency can seem like other conditions. That includes cerebral palsy, epilepsy, and other genetic disorders. Your doctor might run blood tests or look at your child’s brain with magnetic resonance imaging (MRI) to rule out other conditions.

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Phenylketonuria (PKU) Treatments

Phe is one of many amino acids that join together to form proteins, and therefore, is found in lots of foods, especially those rich in protein such as meat, eggs and fish, as well as artificial sweeteners like Aspartame.

Low Protein Diet

One of two medications are approved to treat PKU is called Sapropterin (Kuvan). This medication comes in pill form and is designed to supplement a low protein in order to treat mild cases.

A low-protein diet is the main treatment for phenylketonuria (PKU). This is because people who have PKU lack an enzyme to properly process the amino acid phenylalanine, a part of protein. Phenylalanine is present in all protein foods and in some nonprotein foods, such as soda pop and artificial sweeteners.

Phe-Free Infant Formula

Babies diagnosed with PKU can start on a Phe-free infant formula immediately. Depending on the case, they may be also able consume some breast milk.

As the child ages some may be able to follow the same meal plan as other adults, however in each case a dietitian who specializes in PKU will choose the right meal plan for your child.

Medications for PKU

Monoamine oxidase inhibitors (MAOIs) are a class of medications that inhibit MAO, the enzyme that breaks down serotonin and dopamine. They, therefore, act to increase the amount of dopamine and serotonin in the brain. Even though MAOIs have not been approved to treat AADC deficiency, they have been prescribed off-label to treat some AADC patients. However, there is limited evidence that MAOIs are effective in treating the symptoms of AADC deficiency.

Intravenous Medication

An alternative medication used to treat PKU is an injection known as Pegvaliase (Palynziq). This expensive treatment is administered in cases where diet alone is insufficient to manage symptoms.

Have questions?

Phenylketonuria (PKU) Frequently Asked Questions

It is possible to treat symptoms of the disease and lead a relatively comfortable lifestyle by maintaining a strict low protein diet. However curing the disease currently isn’t possible, and those suffering from PKU must stick to their diet for life.

Like with many diets, the most accessible and effective treatment, people often turn to family and friends for support. Whilst those around you may not benefit from adhering to the same low-protein diet designed to combat PKU, simply having a dieting partner for support can help each other meet goals, stay positive, and ultimately stick with the diet plan you’ve devised.

Regardless of treatment, PKU does not typically shorten a patients lifespan. However it can lead to intellectual disabilities. 

Whilst the estimates vary, it is often cited that PKU affects around 0.45 million people globally. 

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