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PKU is an inherited disorder, which prevents your body to break down Phenylalanine (Phe), an amino acid found in food protein. High levels of Phe build up in the blood and cause brain-associated problems especially during childhood, but also during adolescence and adulthood.

PKU directory

Facts

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Building an independent life

Facts for teenagers with PKU

Phenylketonuria or PKU is an inherited disorder, which prevents your body to break down Phenylalanine (Phe), an amino acid found in food protein. High levels of Phe build up in the blood and cause brain-associated problems especially during childhood, but also during adolescence and adulthood.

Achieving better PKU management

Learn how it’s possible to be healthy and enjoy life to the full by managing your blood Phenylalanine (Phe) levels treatment, which has been adapted to suit your lifestyle.

Guide for teenagers with PKU

Learn why it’s important to remain committed to your diet whilst being independent.

Treatment information for teenagers with PKU

Find out how to achieve low Phe goals more easily.

Tips and tools for teenagers

Coping with PKU whilst being independent.

PAH (Phenylalanine Hydroxylase)

An enzyme which works together with Tetrahydrobiopterin (BH4) to convert Phenylalanine (Phe) to Tyrosine (Tyr) in the liver. A deficiency in PAH results in high Phenylalanine levels in the blood, which is the biochemical hallmark of Phenylketonuria (PKU).

Phenotype

An observable characteristic or trait of an organism. Phenotypes result from the expression of an organism’s genes as well as the influence of environmental factors.

phenylalanine (Phe) tolerance

The quantity of Phe a patient may consume without a significant increase in her or his target blood Phe levels. Usually expressed as daily intake.

Phenylalanine (Phe)

A building block of protein, and one of the 10 essential amino acids. An inability to metabolize excess phenylalanine is the characteristic feature of Phenylketonuria (PKU). When the blood concentration of Phenylalanine exceeds what is considered a healthy level, excess amounts may build up in the brain, causing mental retardation.

Phenylalanine Hydroxylase

See PAH.

Phenylketonuria

See PKU.

PKU (Phenylketonuria)

An inherited metabolic defect in protein metabolism. In PKU, the Phenylalanine Hydroxylase (PAH) enzyme is unable to convert Phenylalanine to Tyrosine, resulting in a build-up of Phenylalanine (Phe) in the blood that eventually passes into the brain, causing mental retardation and other neurological problems.

Protein

A type of molecule produced by the body from Amino acids.

Neurotoxic

A substance or agent which is damaging to the brain.

Nutritionist

See dietitian/nutritionist.

Large neutral amino acids (LNAA):

Large neutral amino acids (LNAA) may also be used in therapy for PKU. LNAA, taken in tablet form, compete with Phe for transport across the blood-brain barrier, reducing the concentration of Phe in the blood.

Gene

A portion of Deoxyribonucleic acid (DNA) which holds the information to build and maintain any element of a living organism. When a gene mutates, it may no longer perform the same function, and often the mutation renders it entirely inactive. In the case of Phenylketonuria (PKU), the gene involved in the production of Phenylalanine Hydroxylase is mutated, causing the liver to produce insufficient amounts of that enzyme, and thus restricting the activity of the metabolic pathway that converts Phenylalanine to Tyrosine.

Genetic counsellor

A healthcare professional who specialises in the education and support of patients and families regarding inherited disorders.

Guthrie test

A blood test, also known as the heel prick test performed on newborn infants in the days immediately after birth to detect genetic disorders, including Phenylketonuria (PKU).

Eczema

A skin condition which causes the skin to appear red, swollen and itchy.

Enzyme

A kind of biological molecule that facilitates certain chemical reactions inside the body. People with Phenylketonuria (PKU) lack a certain enzyme called Phenylalanine Hydroxylase (PAH).

Carrier

A person who carries a gene that may cause disorder, but who does not suffer from the disorder itself. A carrier may pass on the defective gene to offspring.

Chorionic villus sampling (CVS)

A prenatal test to determine genetic disorders in the foetus, by sampling a small piece of placenta tissue.

Classic PKU

The most severe form of Phenylketonuria (PKU). People with classic PKU typically have a blood Phenylalanine (Phe) level of >1200 μmol/L when not on a Phe-restricted diet and typically tolerate less than 250–350 mg of dietary Phe a day.

Cofactor

A molecule that combines with an enzyme in order for that enzyme to function. The cofactor of Phenylalanine (Phe) is Tetrahydrobiopterin (BH4).

BH4 (Tetrahydrobiopterin)

An enzyme cofactor that works together with Phenylalanine Hydroxylase to convert Phenylalanine to Tyrosine in the liver. Without the action of both Phenylalanine Hydroxylase and Tetrahydrobiopterin, the chemical process cannot take place, resulting in an accumulation of excess phenylalanine.

BH4 deficiency

A deficiency of the naturally produced BH4 cofactor, caused by mutation in one or more of the enzymes involved in synthesis or regeneration. BH4 deficiency is not the same disorder as Phenylketonuria (PKU).

Amino acid

A type of molecule found inside protein. There are 20 amino acids that are considered standard. Of those, 10 are essential to a healthy diet because the body is unable to produce them. Among the 10 essential amino acids is Phenylalanine.

Amniocentesis

A prenatal test in which cells are collected from the amniotic sac in order to detect chromosomal abnormalities.

Amniotic sac

The thin-walled bag that contains the protective liquid that surrounds the foetus during its development in the womb.