The hereditary metabolic disorder phenylketonuria (PKU) occurs rarely, but if a child becomes ill, it requires a consistent diet from the first minute to prevent damage to brain development and complications that may arise.
What is phenylketonuria?
Phenylketonuria is a hereditary metabolic disease in which a certain protein component accumulates in the body, limiting brain development in children in particular. In the Federal Republic of Germany, statistically only one child out of 10,000 is affected. If the disease is diagnosed early in this child, phenylketonuria can be treated and the child can develop completely normally.
Causes
The cause of phenylketonuria is a genetic defect. This causes the protein component phenylalanine, which is found in all protein-containing foods and is therefore ingested with food, to be unable to be broken down. In healthy people, an enzyme is active for this, but in people with phenylketonuria, depending on the severity, it only functions partially or has completely stopped functioning.
Symptoms, complaints, and signs
If the condition is not recognized and treated immediately after birth, the first signs appear around three months of age. Brain maturation is disturbed, and the brain does not grow adequately, which is visible in older children by a much smaller head. Mental development falls behind. By the time puberty is reached, there are severe mental disabilities. 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 tense up like cramps (spasticity), making normal movements difficult. Furthermore, behavioral disorders in the form of hyperactivity and aggressiveness occur. The children tend to have uncontrolled outbursts of rage. A typical sign of PKU is the smell of acetone emitted 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 present in urine. The appearance of those suffering from PKU is characteristic. Since their oranism cannot sufficiently produce the pigment melanin, they often have white-blond hair, very light sensitive skin and light blue, transparent shimmering eyes. The pigment disorder can cause eczema-like skin rashes. The severity of the symptoms depends on how severely the metabolism is impaired and deviates from the norm.
Diagnosis and course
Phenylketonuria can be detected by a blood test, which is usually performed during newborn screening as part of the so-called U2 screening examination. Among other things, the blood test performed here determines the infant’s phenylalanine level. Since the metabolism is disturbed in the case of phenylketonuria and the phenylalanine can no longer be broken down, it is increasingly deposited in the blood and can be detected here. An elevated phenylalanine level with more than 1 to 2 milligrams per deciliter in the blood indicates a disease with phenylketonuria. If phenylketonuria is suspected during pregnancy, DNA testing of the infant can be performed prenatally with the help of an amniocentesis and a diagnosis can be made. If phenylketonuria is diagnosed, further tests are then performed to determine the severity of the disease, which is the basis for treatment. If phenylketonuria is not treated, the first symptoms of the metabolic disease appear after about three months and quickly lead to serious complications, including delayed mental development to severe mental retardation, disturbed muscle tension to epileptic seizures.
Complications
Phenylketonuria must definitely be treated immediately after the child is born. If this treatment is not given, there may be serious problems with the child’s growth and development that cannot be compensated for later. Those affected usually suffer from a metabolic disorder due to phenylketonuria. This also leads to increased irritability, so that the children appear aggressive.A delay in motor and mental development may also become apparent and significantly reduce the quality of life of the affected person. In many cases, the parents also suffer from depression or other psychological upsets. The affected persons also show an unpleasant body odor, so that affected children and adolescents can become victims of teasing or bullying. Furthermore, epileptic seizures also occur, which in the worst case can lead to death. Pigmentation disorders can also occur in the child. Treatment of phenylketonuria is not associated with complications. Proper nutrition can prevent the maldevelopments, so that there are no more complications in adulthood.
When should you go to the doctor?
Since phenylketonuria can cause severe damage to the child’s brain, this condition must be treated immediately in any case. Early diagnosis is very important to prevent further complications or impaired development of the child. As a rule, phenylketonuria is manifested by slowed development of the child, and mental retardation and epileptic seizures also play a role. In the event of an epileptic seizure, the emergency doctor should be called or the hospital visited immediately, as this is the only way to prevent further damage. In the younger years, phenylketonuria often leads to outbursts of rage or severe behavioral disorders. If these symptoms also occur, a visit to a doctor is necessary. Also, pigmentary disorders or spots on the skin may indicate this disease. The treatment of phenylketonuria depends on the exact symptoms and is carried out by various specialists. Often, psychological treatment is also useful, in which parents or relatives can also participate. With early diagnosis and treatment, the patient’s life expectancy is usually not negatively affected.
Treatment and therapy
Once phenylketonuria has been diagnosed, it can usually be treated quite well, so that children do not have to suffer from maldevelopment of the brain and instead develop completely normally mentally. However, this is only possible with a consistently followed low-phenylalanine diet. There is no other therapy option, such as medication, to treat phenylketonuria and prevent damage to the brain. It is particularly important to almost completely avoid foods containing phenylalanine during the time when the brain is developing – that is, from birth to puberty. The earlier the diet is started, the better the course of phenylketonuria. For this reason, the diet is usually started from the birth of a newborn, and infants are given a special infant formula containing hardly any phenylalanine instead of breast milk. Even though the low-phenylalanine diet is particularly important until puberty, doctors recommend a lifelong diet with little phenylalanine to avoid being limited by the condition into old age. However, it is important in the diet for the therapy of phenylketonuria that the diet contains little phenylalanine, but does not completely prevent the intake of phenylalanine. This is because phenylalanine is a vital amino acid that is particularly necessary for growth, even in children suffering from phenylketonuria. However, a certain value in the blood should not be exceeded. Therefore, people with phenylketonuria disease must undergo regular blood monitoring.
Outlook and prognosis
The prognosis for classic phenylketonuria is markedly good if the diagnosis is made early, preferably in the newborn infant. If a low-phenylalanine diet is given in early infancy, no physical or mental impairments are expected. Affected individuals have a normal life and an average life expectancy. An important prerequisite for a positive prognosis is strict adherence to the diet, especially during the first six years of life, when the brain is developing in a particularly pronounced way. Women with phenylketonuria can also become pregnant and have children of their own. Although it is a hereditary metabolic disorder, no harm is expected to the child. However, the diet must be followed consistently during pregnancy.Without the low-phenylalanine diet, the disease leads to brain development disorders already in early childhood. Neurological abnormalities can be seen as early as 4 months of age. 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, behavioral disorders and motor disabilities may occur. A special case is the atypical form of phenylketonuria, which is characterized by a deficiency of coenzyme BH4 (tetrahydrobiopterin). The prognosis of mental development in these patients cannot be assessed uniformly. Despite early diet, damage to the nervous system may occur.
Prevention
Because phenylketonuria is a hereditary metabolic disorder, there is no way to prevent phenylketonuria. However, those who have phenylketonuria can prevent symptoms and complications that usually occur with phenylketonuria by eating a diet low in phenylalanine. To protect one’s children from the consequences of a disease with phenylketonuria, affected individuals who are already pregnant, whose partner is pregnant, or who are planning to become pregnant should be sure to strictly adhere to a low-phenylalanine diet plan. In the event that the child becomes ill, a low-phenylalanine diet should also be followed for the child’s well-being.
Follow-up
Because phenylkentonuria is one of the inherited metabolic disorders and cannot be cured causally, but only treated, follow-up and treatment are largely the same. First and foremost, this includes a low-phenylalanine diet and regular monitoring of the PA level in the blood. These measures must be followed especially strictly until the age of six, but are necessary throughout life. In atypical phenylketonuria, the coenzyme BH4 must also be supplemented. If the treatment was started too late, the follow-up may also cover already existing damages. These are usually in the area of brain development and can vary in severity. Here, the early start of support measures (for example, occupational therapy) can be useful to counteract behavioral problems. These include sleep problems, control compulsions, self-damaging or antisocial behavior, the severity of which can often be successfully mitigated. For motor disorders, targeted physical therapy can improve symptoms. If the prescribed measures are adhered to, it is now possible for many patients to lead a largely normal life. When puberty is reached, the most sensitive phase is completed. Major, neurological defects are then usually no longer to be expected, although brain chemistry may be temporarily impaired by fluctuations in PA levels. This is helped by the supply of dopamine preparations.
Here’s what you can do yourself
In classic phenylketonuria, the focus is on adherence to a lifelong vegan diet without the phenylalanine source aspartame. Newborns are fed only phenylalanine-free bottle-feeding. Fruit and vegetable jars are suitable as complementary food. Parents of children suffering from PKU must calculate the phenylalanine content of all foods fed and consistently comply with limit values. Later, the infant food is replaced by a protein powder specially developed for this disorder. 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 accustom even the youngest child to the smell and taste of the powder in a playful manner. In the meantime, there is a wide range of training and cooking courses for affected children of all ages. These educational measures gradually promote personal responsibility. At the same time, they support a positive approach to dietary restrictions. Low-phenylalanine convenience foods enable young patients to participate in outings and school trips. Parents of sick children are exposed to strong organizational and psychological stress. It is helpful for them to exchange information with fellow sufferers in self-help groups. Adult phenylketonuria patients who wish to have children must take special care in family planning: Only adherence to a strict diet ensures normal phenylalanine levels during pregnancy.Normal values are already mandatory at the time of conception to avoid serious damage to the unborn child.
