Hyperphenylalaninemia is a congenital amino acid metabolic defect. Those affected can not break down the amino acid phenylalanine, which leads to accumulation in the organism. The causes are usually autosomal recessive inherited mutations in the gene for the enzyme phenylalanine hydroxylase (classical form) or disturbances of the coenzyme tetrahydrobiopterin (atypical form).
The high phenylalanine level has a strong neurotoxic effect in children, causing brain development disorders and destruction of the medullary sheaths. The children are born healthy, first symptoms show up in the course of development in normal diet. The main symptom is a severe mental retardation, sufferers usually have an intelligence quotient below 50.
It can lead to behavioral disorders such as increased aggressiveness, hyperactivity, autism or psychosis. Other symptoms include paralysis, seizures, tremor and hypothyroidism. The children have a pale skin with eczema, colorless hair and fall through a musty body odor.
Affected pregnant women often suffer from miscarriages or growth delays of the fetus. Due to the severity of the symptoms, phenylalanine levels are tested by default in neonates. With appropriate therapy, the children develop normally and show no impairment, the prognosis is good.
Already suffered brain damage is no longer reversible by a therapy; Untreated patients have a poor prognosis due to severe retardation.