phenylketonuria: Overview, Symptoms, Causes, Treatment, Topics

What Is Phenylketonuria?

Phenylketonuria is a result of a genetic disorder wherein the body cannot metabolise phenylalanine properly. This inborn metabolic perturbation results from a mutation within the PAH gene, which encodes the phenylalanine hydroxylase enzyme. In an autosomal recessive pattern, the individual has to inherit two defective copies of the PAH gene, one from either parent, to be inflicted with the disorder. A carrier-causing mutation usually does not result in symptoms and is carried only within one copy of the gene, which can be passed on to offspring.

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This Story also Contains

1. What Is Phenylketonuria?
2. Symptoms And Diagnosis Of Phenylketonuria
3. Management And Treatment Of Phenylketonuria

PKU pathophysiology is the key point in the metabolism of phenylalanine to tyrosine, catalysed by phenylalanine hydroxylase. Genetic mutations that culminate in this deficiency or dysfunction of this enzyme lead to the accumulation of the amino acid phenylalanine in both blood and the brain. Excessive levels of phenylalanine are neurotoxic, leading to impairment in normal cognitive development and intellectual disability with associated neurological defects. This accumulation will disturb normal brain development and function. Thus, early and continuing management of the disorder is important.

Symptoms And Diagnosis Of Phenylketonuria

The symptoms of PKU usually start to appear in the first few months of life, though most conspicuously if left untreated.

• Early symptoms are marked by developmental delay and a decrease in intellectual function.
• Behavioural problems are also observed; symptoms include hyperactivity, social withdrawal, and mood swings.
• Physical symptoms may include eczema, a musty odour of the skin and urine from the excess phenylalanine metabolites, and lighter skin and hair than unaffected siblings due to lessened melanin production.

Several methods do PKU diagnosis, the first one being done in most countries as the obligatory PKU newborn screening.

• High phenylalanine might be indicated using a few blood drops then confirmed by the blood test with precise good measurement of phenylalanine and tyrosine.
• Genetic testing will go ahead to identify specific mutations in the gene, therefore conclusively making the diagnosis and informing family planning.
• Early detection ensures that treatment is instigated before significant neurological injury has developed.

Management And Treatment Of Phenylketonuria

The hallmark treatment for PKU is dietary management. This is a very strict diet that restricts phenylalanine to very low levels except for some high-protein foods like meat, fish, eggs, dairy products, nuts, and beans. In the majority of cases, low-phenylalanine medical foods and amino-acid-based foods are required to provide phenylalanine levels that are nutritionally adequate and will help to ease metabolic control of phenylalanine to a safe level. Dietitians modify and individualise the diet according to each condition and track the nutrition of people afflicted with these conditions.

Medical therapy for PKU includes the use of sapropterin dihydrochloride (BH4)—a man-made type of cofactor, which can increase the residual activity of phenylalanine hydroxylase in some patients. It allows more liberalised dietary treatment with less pronounced blood concentrations of phenylalanine. Enzyme substitution therapy meets an option for the occurrence of an alternative route to degrade phenylalanine in the blood. Such medical manipulations, combined with the control of nutrition, provide a universal tool to control PKU and improve the quality of life among those suffering.

Adequate follow-up and monitoring constitute important aspects of the management of PKU. Periodic blood assays can monitor phenylalanine levels to educate the patient whether their dietary and medicinal treatments are working or need some adjustments. Lifelong treatments are in order as control of phenylalanine levels throughout life prevents neurologic and cognitive complications.

Conclusion

Phenylketonuria is a serious genetic disorder that can give rise to acute brain damage and neurologic impairment if untreated. The best quality of life depends upon an early diagnosis through newborn screening followed by management through dietary and medication interventions. Early recognition and diagnosis of PKU with expanded awareness and education may increase its detection in the early stage and thus provide treatment. The continued research on PKU brings new therapies that may improve outcomes. A better understanding of PKU helps not only oneself but also other people afflicted by this dreaded disease and also enhances a better understanding of metabolic and genetic disorders in general.