1. What is Phenylketonuria?
Phenylketonuria or PKU is an inherited disorder that affects the chemistry of the organism and if not treated with the correct timing, it causes mental retardation. Fortunately, thanks to habitual neonatal it is now posible to diagnose and treat n an early stage most of the babies affected by this disorder and enable tham to grow and develop with a normal intelligence.
In the USA, about 1 of 15,000 babies are born with PKU. This disorder happens in all ethnic groups, although it is more common in individuals whose ancestros come from Northern Europe or that where natives from the Status than those with an afroamerican, Hispanic or Asian origin.
2. What is PKU?
Due to lacking or to an insufficient amount of an enzime, PKU children can not a party of the Phenilalanine protein, existing in most foods. If the correct treatment is not delivered, the phenilalanine acumulates in thr blood flor and produces brain damage and mental retardment.
3. How does PKU affect a child?
During the first months of life, PKU children seem healthy. But if they do not receive treatment, they begin to loose interest in the environment between the three and six months of life, and when reaching one year, it becomes obvious that they have Developed a devlopment retardment. PKU children without treatment that have had an injury int the central nervous system are often irritable, restless and destructive. They can smell somehow like moldy or humod and may have dry skin, eruptions or seizures. They normally present a helathy physical development and tend to have blonder hair than their brothers and sisters.
4. Who suffer from PKU?
PKU is inherited when both parents have the PKU gene and transmit it to their baby. When one of the parents has the PKU gene but not the disease, he/she is known as a “carrier” of the same.A carrier has a normal gene and a PKU gene in each cell. The carrier’s health does not undergo no effect because of the presence of Duch gene. When both parents are carriers, the probability of transferring the PKU gene to their baby, o transmiten a su bebé. Cuando uno de los padres tiene el gen de la PKU pero no padece la enfermedad, se dice que es “portador” de la misma. Un portador tiene un gen normal y un gen con PKU en cada célula. La salud de los portadores no sufre efecto alguno por la presencia de este gen. Cuando ambos padres son portadores, la probabilidad de que ambos transfieran el gen de la PKU a su bebé, haciendo que este nazca con la enfermedad, es de una entre cuatro (25 por ciento). Dos de cada cuatro bebés heredan el gen de la PKU de uno de sus padres y el gen normal del otro, convirtiéndolos en un portador como sus padres. También hay una probabilidad de una entre cuatro de que cada uno de ellos le transfiera un gen normal y de que el niño no tenga la enfermedad ni sea portador. Estas probabilidades son iguales durante todos los embarazos.
5. Do all babies undergo tests to detect PKU?
All states and territories of the makes test to babies before they leave the hospital. This was the first test for newborns to be performed in the country. It was developed with the help of March of Dimes and is delivered since the 60’s. It ahas already saved thousands of children from mental retardment.
6. How is this test done?
A very small puncture is done in the heel of the baby to extract a few blood drops, (the same teat may be used to diagnose other congenit disorders on the organism chemistry). Normally, the simple is sent to a regional medical lab to acknowledge if the quantity of phenylalanine is greater than normal, and the results are sent to the baby’s pediatrician. If the results are not normal, additional tests are done to determine if the baby has PKU or if his high phenylaline levels are because of any other reason.
The test is very precise when done following the indications and the baby is over 24 hours of age but less than seven days. However, leaving the hospital befote the baby is 24 hours old is becoming more common, and many babies undergo the test befote their first 24 hours of life. This is too early to detect all of the babies with high phenylaline levels, and some of them pass unnoticed. The USA Pediatric Academy recomends taking the test again betwwen the first and second week of the baby’s life on babies that undergo the first test befote they are 24 hours old
7. Is it posible to prevent PKU symptoms?
Yes. It is posible to prevent mental retardation completely if the baby is treated with a low phenylalanine special diet within the first 7 to 10 days of life.
At first, the baby is fed a special formula that contains proteins but without phenylalanine. Only small doses of breast milk or normal baby formula is administered in order to not provide him with more phenilalanine than what he actually can tolerate. Further on, some vegetables, fruits, some grains (certain cereals and pastas for example) and other low phenilalanine foods are added to the diet, but he never can be feeded with normal milk, cheese, eggs, meat, fish nor other high proteinic food. As proteins are essential for the child’s development qand growth he will have to continue taking one of the special formulas containing a lot of proteins and basic nutrients but having few or no phenylalanine. Drinks and foods containing the artificial edulcorant Aspartame (containing phenilalanine and commercialised as NutraSweet or Equal) must be always avoided.
It is necessary to monitor PKU children and adults at a clinic or medical center specialised in this disorder. The diet must be individual, in accordance with the amount of phenylalanine each can tolerate, their age, weight and other factors. All people under this disorder must perform regular blood tests to check if the phenylalanine levels are too high or low. Concerning babies, the tests can be weekly during the first year and the once or twice per month during chilhood. The diet must be modified as necessary.
PKU individuals must keep a restricted diet during childhood and adolescense, and probably throughout life (although it is possible to relax the diet in some cases while reaching adulthood). Until the 80’s, doctors thought that PKU children could give up the diet without risk when they were about 6 once the brain had already grown. However, high phenylalanine levels in childre and teenagers can diminish the I.Q. and cause learning and behaviour problems in most of PKU children (although it is possible not in all of them). Pku children’s parents and PKU adults must answer their questions about the diet and treatment with the specialists of a specialized PKU clinic.
8. What is maternal PKU?
It is stimated that there is about 3,000 young healthy women with fertile age who have been succesfully treated from PKU in the US. Most of them abasndoned their special diet during childhood because during that period doctors thought that it did not impla any risks.
When these young women get pregnat while feeding from a normal diet, phenylalanine concentration in blood is considerable.High phenylalanine levels in the mother’s blood are very harmful for the fetus. In about 90% of these cases, babies suffer from retardation and/or are born with a small head (microcephaly). Many are also born with cardiac defects, low weight and characteristical factions. As most of these babies do not inherit PKU, actually their brain damage is wholy because the high phenylalanine levels of the mother during pregnancy, Pku diet does not help them at all.
Fortunately, there is a way to help prevent retardation and other issues that arise on babies of PKU mothers. Presently, it has been proven that these young women must resume their special diets three months before pregnancy and follow it during the latter. This is the way to take control of their phenylalanine blood levels in order to have a healthy baby. They will need to take boold controls at least once per week during the whole pregnancy to ensure that phenylalanine blood levels are not too high.
March of Dimes recommends all young women that ackowledge or suspect having being treated from PKU as children to contact their health professional or their clinic before attempting the conception in order ot measure their phenylalanine levels and, if needed, start the special diet.
Some women have a non-diagnosed PKU, representing a risk for their babies. Algunas mujeres tienen PKU no diagnosticada, lo cual puede representar un riesgo para su bebé. These women, who normally have not been under studies when born, the affection normally is mild and can only diagnosed after the baby is born with his PKU related effects. In order to prevent these congenit deffects some doctors recommend women with PKU risk, as those who have family history of this disorder, to perform studies to start the special.
9. What’s new on PKU investigations?
Investigators are studying the long term prognosis of children borned from PKU motores treated during pregnancy. Even if these children do nor present normally congenit defects, the investigators want to know if they are capable of reaching their top cognotive potencial.
Other investigators are focused on the development of a versiono f the mailing enzyme by jeans of gentic engineering, that eventually will enable the individuals by PKU to have a normal diet.. March of Dimes and other investigators are also exploring the possibility of treating PKU with genetic therapy.
- Tríptico PKU pdf, 172 KB