Phenylketonuria (PKU)

The hereditary metabolic disease Phenylketonuria (PKU) rarely occurs, but in the case of a child's illness, it requires consistent nutrition from the first minute in order to prevent damage to the development of the brain and the associated complications.

What is phenylketonuria?

If the condition is not diagnosed and treated immediately after birth, the first signs will show around three months of age.Brain maturation is disturbed, the brain does not grow adequately, which is visible in older children by a significantly smaller head.
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Phenylketonuria is a hereditary metabolic disease in which a certain protein component accumulates in the body, which primarily restricts brain development in children.

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In the Federal Republic of Germany, only one child out of 10,000 is statistically affected. If this child is diagnosed with the disease early, phenylketonuria can be treated and the child can develop completely normally.

causes

The cause of Phenylketonuria is a genetic defect. This means that the protein component phenylalanine, which occurs in all protein-containing foods and is therefore ingested with food, can no longer be broken down. In healthy people, an enzyme works for this purpose, which in people with phenylketonuria, depending on the severity, only partially works or has completely stopped working.

Symptoms, ailments & signs

If the condition is not diagnosed and treated immediately after birth, the first signs will show around three months of age. Brain maturation is disturbed, the brain does not grow adequately, which is visible in older children by a significantly smaller head. The mental development falls behind. When they reach puberty they have severe intellectual disabilities.

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Due to the damage to the brain cells, the children suffer from hyperexcitability, which often causes epileptic seizures. The muscle cells are also damaged by the disease. The muscles tighten like spasms (spasticity), which makes normal movement more difficult. Furthermore, behavior disorders in the form of hyperactivity and aggressiveness occur. The children are prone to uncontrolled outbursts of anger.

A typical sign of PKU is the odor of acetone given off by those affected. It is caused by the formation of phenyl acetate in the body. This substance is excreted through the sweat glands and is also contained in the urine. The appearance of those suffering from PKU is characteristic.

Since their oranism cannot sufficiently produce the pigment melanin, they often have white-blonde hair, very light, sensitive skin and light-blue, transparently shimmering eyes. The pigmentation disorder can cause eczema-like skin rashes. The severity of the symptoms depends on how severely the metabolism is restricted and deviates from the norm.

Diagnosis & course

The Phenylketonuria can be determined by a blood test, which is usually carried out in the newborn screening as part of the so-called U2 preventive examination. The blood test carried out here will determine, among other things, the infant's phenylalanine level.

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Since the metabolism is disturbed in a disease with phenylketonuria and the phenylalanine can no longer be broken down, it is increasingly deposited in the blood and can be detected here. An increased phenylalanine value of 1 to 2 milligrams per deciliter in the blood indicates a disease with phenylketonuria.

If phenylketonuria is suspected during pregnancy, an amniotic fluid test can be used to perform a prenatal DNA test on the infant and make a diagnosis. If phenylketonuria is diagnosed, additional tests will be done to determine the severity of the condition, and treatment will be targeted.

If phenylketonuria is not treated, the first symptoms of the metabolic disease appear after about three months, which quickly lead to serious complications, including delayed mental development through to severe intellectual disabilities, impaired muscle tension through to epileptic seizures.

Complications

In any case, phenylketonuria must be treated immediately after the child is born. If this treatment is not carried out, it can lead to serious complaints during the growth and development of the child, which cannot be compensated for later. Those affected usually suffer from a metabolic disorder due to phenylketonuria.

It also leads to increased irritability, so that the children appear aggressive. A delay in motor and mental development can also become apparent and significantly reduce the quality of life of the person concerned. In many cases, the parents also suffer from depression or other psychological disorders. Those affected also show an unpleasant body odor, so that affected children and adolescents can become victims of teasing or bullying.

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Furthermore, epileptic seizures occur, which in the worst case can lead to death. Pigment disorders can also occur in the child. Treatment for phenylketonuria is not associated with complications. Proper nutrition can prevent undesirable developments so that there are no more complications in adulthood.

When should you go to the doctor?

Since phenylketonuria can lead to severe damage to the child's brain, this disease must be treated immediately in any case. An early diagnosis is very important to prevent further complications or impaired development of the child. As a rule, phenylketonuria manifests itself as a slower development of the child; intellectual disabilities and epileptic seizures also play a role.

In the event of an epileptic seizure, call an emergency doctor or go to the hospital immediately, as this is the only way to avoid further damage. At a young age, phenylketonuria often leads to outbursts of anger or severe behavioral disorders. If these symptoms also occur, a visit to a doctor is necessary. Pigment disorders or spots on the skin can also indicate this disease.

The treatment of phenylketonuria depends on the exact symptoms and is carried out by various specialists. Psychological treatment, in which parents or relatives can also participate, is often useful. With early diagnosis and treatment, the life expectancy of the patient is usually not negatively affected.

Treatment & Therapy

When a Phenylketonuria has been diagnosed, it can usually be treated very well, so that children do not have to suffer from abnormal brain development and instead develop completely normally mentally.

However, this is only possible with a consistently adhered to low-phenylalanine diet. There is no other therapeutic option, for example drug-based, to treat phenylketonuria and avoid damage to the brain. It is particularly important to almost completely avoid foods containing phenylalanine during the period in which the brain is developing - i.e. in the period from birth to puberty.

The earlier the diet is started, the better the progression of phenylketonuria. For this reason, the diet is usually started as soon as a newborn is born, and instead of breast milk, infants are given a special formula that hardly contains any phenylalanine. Even if a diet low in phenylalanine is particularly important up to puberty, doctors recommend a lifelong diet low in phenylalanine in order not to be restricted by the disease into old age.

However, it is important in the diet for the treatment of phenylketonuria that the diet contains little phenylalanine, but does not completely prevent the absorption of phenylalanine. Because phenylalanine is a vital amino acid that is particularly necessary for the growth of children suffering from phenylketonuria. However, a certain value in the blood should not be exceeded. Therefore, people with phenylketonuria must have regular blood tests.

Outlook & forecast

The prognosis for classical phenylketonuria is extremely good if the diagnosis is made early, if possible in the newborn child. If a low-phenylalanine diet is given in early infancy, no physical or mental impairments are to be expected. Those affected have a normal life and an average life expectancy.

An important prerequisite for a positive prognosis is strict adherence to the diet, especially in the first six years of life when the brain is developing particularly well. Women with phenylketonuria can also become pregnant and have children of their own. Although it is a hereditary metabolic disease, no harm is to be expected for the child. However, the diet must be followed consistently during pregnancy.

Without the low-phenylalanine diet, the disease leads to disorders of brain development in early childhood. Neurological abnormalities can already be recognized from the 4th month of life. Since the brain damage is irreversible, there is no prospect of a cure. The intelligence quotient will usually be permanently below the norm. In addition, seizures, behavior disorders, and motor disabilities can occur.

A special case is the atypical form of phenylketonuria, which is characterized by a deficiency in coenzyme BH4 (tetrahydrobiopterin). The prognosis of intellectual development in these patients cannot be consistently assessed. Despite an early diet, damage to the nervous system can occur.

prevention

Since it is a Phenylketonuria If it is a hereditary metabolic disease, there is no way to prevent phenylketonuria. However, if you have phenylketonuria, a diet with foods low in phenylalanine can prevent symptoms and complications that usually occur with phenylketonuria.

In order to protect their own children from the consequences of a disease with phenylketonuria, people who are already pregnant, whose partner is pregnant or who are planning a pregnancy should strictly adhere to a low-phenylalanine diet. If the child becomes ill, attention should be paid to a diet low in phenylalanine for the child's wellbeing.

Aftercare

Since phenyl kentonuria is one of the hereditary metabolic disorders and cannot be cured but only treated, aftercare and treatment are largely identical. This primarily includes a low-phenylalanine diet and regular monitoring of the PA level in the blood. These measures must be strictly observed up to the age of six, but are necessary for life.

With atypical phenylketonuria, the coenzyme BH4 must also be supplemented. If treatment was started too late, follow-up care can also extend to existing damage. These are mostly in the area of ​​brain development and can vary in severity.

The early start of support measures (e.g. occupational therapy) can be useful in order to counteract behavioral disorders. These include sleep problems, the need to control, self-damaging or antisocial behavior, the severity of which can often be successfully mitigated. In the case of motor disorders, targeted physiotherapy can improve the symptoms.

If the prescribed measures are observed, it is now possible for many patients to lead a largely normal life. When you reach puberty, the most sensitive phase is over. Larger, neurological defects are then usually no longer to be expected, even if fluctuations in the PA level can temporarily impair brain chemistry. The intake of dopamine preparations helps against this.

You can do that yourself

With classic phenylketonuria, adherence to a lifelong vegan diet without the phenylalanine source aspartame is in the foreground. Newborns are fed exclusively with phenylalanine-free formula. Glasses of fruit and vegetables are suitable as complementary foods. Parents of children suffering from PKU must calculate the phenylalanine content of all food they feed and consistently adhere to limit values.

Later the baby food will be replaced by a protein powder specially developed for this disease. The amino acid mixture for PKU patients must be added to every meal. It forms the lifelong main component of the necessary low-phenylalanine diet. It is therefore advisable to get the toddler used to the smell and taste of the powder in a playful way.

There is now a wide range of training courses and cooking courses for affected children of all ages. These pedagogical measures gradually promote personal responsibility. At the same time, they support a positive handling of nutritional restrictions. Ready-made products with a low phenylalanine content enable young patients to take part in excursions and school trips. Parents of sick children are exposed to severe organizational and psychological stress. It is helpful for them to exchange ideas with fellow sufferers in self-help groups.

Adult phenylketonuria patients who wish to have children must take particular care when planning their families: only adherence to a strict diet ensures normal phenylalanine levels during pregnancy. Normal values ​​are absolutely necessary at the time of conception in order to avoid serious damage to the unborn child.