PKU

PKU (PHENYLKETONURIA)

* an inborn error in metabolism
* people with PKU cannot break down the amino acid phenylalanine, which then builds up in their blood and brain which can lead to brain damage.

an inherited disorder (in autosomal recessive manners)

* both parents must carry one deflective copy of the gene that produces phenylalanine hydroxylase

in normal conditions

Our bodies break down the protein in foods, such as meat and fish, into amino acids, which are the "building blocks" of protein.

These amino acids are then used to make our own proteins. Any amino acids that are not needed are broken down further and removed from the body.

* DIAGNOSING PKU IN THE UK

At around 5 days old, babies are offered a newborn blood spot screening to test for PKU and many other conditions. This involves pricking your baby's heel to collect drops of blood to test.

If PKU is confirmed, treatment will be given straight away to reduce the risk of serious complications. Treatment includes a special diet and regular blood tests.

* PHENYLALANINE METABOLISM

phenylalanine is an essential amino acid:


1. 50% of dietary intake required for protein synthesis
2. 50% for synthesis of tyrosine and other metabolites

used for the synthesis of tyrosine, dopamine, melanin and thyroxine therefore being important for several different pathways

WHAT DOES PHENYLALANINE SYNTHESISE?

1. tyrosine,
2. dopamine
3. melanin
4. thyroxine

therefore being important for several different pathways

WHAT HAPPENS WHEN PHENYLALANINE CAN'T BE BROKEN DOWN

* phenylalanine forms phenylpyruvic acid>>>
* >>>this causes PKU to develop>>>
* >>>PKU prevents the synthesis of tyrosine, dopamine, melanin and thyroxine

SYMPTOMS

does not cause symptoms if ONLY treatment has started early. WITHOUT treatment, PKU can damage the brain and nervous system>>>leads to learning difficulties

symptoms of untreated PKU include:

1. temper tantrums and episode of self harm
2. fairer skin, hair and eyes than siblings who do not have the condition (phenylalanine is involved in the body's production of melanin, the pigment responsible for skin and hair colour)
3. eczema
4. repeatably being sick
5. jerking movements in arms and legs
6. tremors
7. epilepsy
8. musty smell to the breath, skin and urine

CLINICAL MANAGEMENT AND TREATMENT

* we must control blood phenylalanine concentrations. once diagnosed, newborns are referred to hospital and monitored for:


1. phenylalanine
2. tyrosine
3. phenylpyruvic acid
4. tetrahydrobiopterin

CLINICAL MANAGEMENT AND TREATMENT - tetrahydrobiopterin

* placed on low phenylalanine diet
* diet is adjusted according to tolerance
* cannot eliminate phenylalanine from diet