PKU is a group of recessively inherited disorders characterized by a deficiency of the liver enzyme phenylalanine hydroxylase, which is necessary for the breakdown of the essential amino acid phenylalanine to tyrosine. As a result of this deficiency plasma

phenylalanine concentration rises and abnormal metabolites are excreted in the urine. This effectively means that in such individuals, normal protein intake produces high levels of toxins which lead to mental retardation, seizures and defects in pigmentation.

PKU is treated by a diet low in phenylalanine, which should be introduced as soon as possible after diagnosis. Blood phenylalanine is reduced in accordance with the MRC working group for PKU guidelines. The evidence so far suggests that children with PKU treated this way can develop normally without symptoms of PKU. It has been observed, however, that even when children with PKU have been diagnosed within the first few weeks of life and treated by diet according to current recommendations they have an IQ below that of their unaffected siblings and slightly below the norm for the general population.

Intellectual outcome is closely related to the quality of their diet and the blood phenylalanine control during the first ten years of life. After adolescence and into adult life risk of intellectual deterioration resulting from high blood phenylalanine declines but it is highly unlikely that this risk ceases to exist.  Follow up of early treated children with PKU has shown that diet discontinuation in childhood presents risks of cognitive and emotional dysfunction in a substantial number of adolescents and young adults. This dysfunction includes IQ loss, mental processing abnormalities, learning difficulties, anxiety and personality disorders. These changes may be so gradual and subtle that they go unnoticed by the individual for many years or are attributed to causes other than the high phenylalanine concentration. Family members and those close to the patient may be the first to note the changes. It is therefore essential that those with PKU who have discontinued diet do not stop attending their PKU clinic.

Only time and careful follow up of those who have relaxed their diet will provide much needed information about the effect of phenylalanine on the adult brain.

Until this information is available, there is international agreement that dietary treatment should continue into adulthood and many centres advocate "diet for life".

PKU pregnancies require specialist management. Pregnancy should be planned and blood phenylalanine concentration controlled in the range of 120 - 250 µmol/L prior to conception and throughout the pregnancy in order to protect the foetus from the teratogenic effects of phenylalanine. These include mental retardation 92%, microcephaly 73%, congenital heart disease 12%, low birth weight 40% and spontaneous abortion 24% (Lenke and Levy, 1980). Frequent monitoring and prompt adjustment of the diet together with good communication, support and encouragement are all necessary throughout pregnancy to achieve optimum control and outcome.

Follow up of the offspring born to PKU mothers to age 14 years, performing neurological and psychological assessments at timed intervals is recommended.

Phenylalanine is an essential amino acid present in all dietary proteins. In order to lower phenylalanine intake in individuals with PKU it is necessary to substitute most dietary protein with a mixture of synthetic amino acids with a similar amino acid profile to dietary protein of high biological value but which excludes phenylalanine. As the diet is very restrictive, the PKU diet is also supplemented with a comprehensive range of vitamins, minerals and trace elements.

Traditional protein substitutes provide a good source of protein but they have several disadvantages which can result in poor compliance and poor metabolic control:

•     The large volume required to provide sufficient protein

•     The inconvenience of their preparation and transportation out of the home

•    They are not all nutritionally complete thus the patient has to take a separate

              vitamin and mineral supplement

Vitaflo have developed a range of protein substitutes for use in PKU, which overcome these disadvantages:

PKU start (diagnosis to 12 months)

PKU gel (1-10 years) and PKU express (8 years +).

PKU gel and PKU express have been specifically designed to be low volume nutritionally complete protein substitutes which have set a new standard of acceptance and convenience in this category of products. It's quick, it's easy and it only takes a minute.

Now available is PKU cooler system giving users a new level of convenience.