Hyperphenylalaninemia (HPA) is the most frequently inherited disorder of amino acid metabolism (prevalence 1:10,000). In France, a nationwide neonatal screening was organized in 1978 to control its efficacy and patient follow-up. Phenylketonuria (PKU) was diagnosed in 81.6% of screened patients, the remaining affected with either non-PKU HPA (17.2%) or with cofactor deficiency (1.1%). French guidelines were established to specify the minimal diagnosis procedures and optimal treatment of patients. A low-phenylalanine diet must be started within the first days of life for all newborns whose blood phenylalanine levels are above 10 mg/dL (600 μmol/L). The dietary control must keep the phenylalanine levels between 2 and 5 mg/dL (120 and 300 μmol/L) until 10 y of age. Thereafter, a progressive and controlled relaxation of the diet is allowed, keeping levels below 15 mg/dL until the end of adolescence and below 20 mg/dL (1200 μmol/L) in adulthood. A lifelong follow-up is recommended for PKU women to prevent for maternal PKU.
Primary hyperphenylalaninemia (HPA)7 are a group of inherited diseases due to defective phenylalanine hydroxylase (PAH) activity resulting in accumulation of phenylalanine in blood and other tissues. In most cases (98% of subjects), HPA results from mutations in the phenylalanine hydroxylase gene. The associated phenotypes range in severity from classic phenylketonuria (PKU) to mild HPA. The remaining cases arise due to a block in the metabolism of the cofactor tetrahydrobiopterin (BH4). BH4 is also the cofactor required for conversion of tyrosine and tryptophan into catecholamine and serotonin. Thus, disorders related to defective metabolism of BH4 could be considered as neurotransmitter diseases (1).
HPA appears as a highly heterogeneous trait with a broad continuum of phenotypes. The term PKU is reserved to the most severe form of the disease. The classical presentation is a progressive encephalopathy in children who have appeared to be normal for the first few months of life. Other symptoms include abnormal electroencephalography with seizures, abnormal behavior with hyperactivity, autistic or schizophrenic signs, eczema and lightly pigmented skin, and a musty odor. A lesser degree of biochemical disturbance is associated with a lower risk of mental handicap. Neurological impairment can be prevented by introduction of a phenylalanine-restricted diet shortly after birth.
Approximately 1 in 10,000 neonates born with PKU or milder forms of HPA are identified in the neonatal period through population-screening programs that have been implemented in various countries to treat affected children as early as possible (2).
Hyperphenylalaninemia (HPA) is the most frequently inherited disorder of amino acid metabolism (prevalence 1:10,000). In France, a nationwide neonatal screening was organized in 1978 to control its efficacy and patient follow-up. Phenylketonuria (PKU) was diagnosed in 81.6% of screened patients, the remaining affected with either non-PKU HPA (17.2%) or with cofactor deficiency (1.1%). French guidelines were established to specify the minimal diagnosis procedures and optimal treatment of patients. A low-phenylalanine diet must be started within the first days of life for all newborns whose blood phenylalanine levels are above 10 mg/dL (600 μmol/L). The dietary control must keep the phenylalanine levels between 2 and 5 mg/dL (120 and 300 μmol/L) until 10 y of age. Thereafter, a progressive and controlled relaxation of the diet is allowed, keeping levels below 15 mg/dL until the end of adolescence and below 20 mg/dL (1200 μmol/L) in adulthood. A lifelong follow-up is recommended for PKU women to prevent for maternal PKU.
Primary hyperphenylalaninemia (HPA)7 are a group of inherited diseases due to defective phenylalanine hydroxylase (PAH) activity resulting in accumulation of phenylalanine in blood and other tissues. In most cases (98% of subjects), HPA results from mutations in the phenylalanine hydroxylase gene. The associated phenotypes range in severity from classic phenylketonuria (PKU) to mild HPA. The remaining cases arise due to a block in the metabolism of the cofactor tetrahydrobiopterin (BH4). BH4 is also the cofactor required for conversion of tyrosine and tryptophan into catecholamine and serotonin. Thus, disorders related to defective metabolism of BH4 could be considered as neurotransmitter diseases (1).
HPA appears as a highly heterogeneous trait with a broad continuum of phenotypes. The term PKU is reserved to the most severe form of the disease. The classical presentation is a progressive encephalopathy in children who have appeared to be normal for the first few months of life. Other symptoms include abnormal electroencephalography with seizures, abnormal behavior with hyperactivity, autistic or schizophrenic signs, eczema and lightly pigmented skin, and a musty odor. A lesser degree of biochemical disturbance is associated with a lower risk of mental handicap. Neurological impairment can be prevented by introduction of a phenylalanine-restricted diet shortly after birth.
Approximately 1 in 10,000 neonates born with PKU or milder forms of HPA are identified in the neonatal period through population-screening programs that have been implemented in various countries to treat affected children as early as possible (2).
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