Summary about Disease
Phenylalanine hydroxylase (PAH) deficiency, most commonly resulting in phenylketonuria (PKU), is an inherited metabolic disorder. It's characterized by a deficiency in the enzyme PAH, which is needed to break down the amino acid phenylalanine. This leads to a buildup of phenylalanine in the blood and brain, which can cause intellectual disability, seizures, and other serious health problems if untreated. The severity of the condition varies depending on the degree of enzyme deficiency.
Symptoms
If untreated, PKU symptoms can include:
Intellectual disability
Seizures
Developmental delays
Behavioral, emotional, and social problems
Psychiatric disorders
Hyperactivity
Skin rashes (eczema)
Musty odor in breath, skin, or urine
Fair skin and blue eyes (due to lack of melanin, which relies on phenylalanine)
Microcephaly (small head size)
Causes
PKU is caused by mutations in the PAH gene. This gene provides instructions for making the PAH enzyme. Mutations in this gene reduce or eliminate the activity of the enzyme. PKU is inherited in an autosomal recessive pattern, meaning both parents must carry a copy of the mutated gene for their child to be affected.
Medicine Used
4. Medicine used
Dietary management: This is the cornerstone of PKU treatment. A low-phenylalanine diet restricts foods high in phenylalanine, such as meat, dairy products, nuts, seeds, and beans. Special formulas provide essential amino acids without excessive phenylalanine.
Kuvan (sapropterin dihydrochloride): This medication helps some individuals with PKU who have some residual PAH enzyme activity. It helps the enzyme work more effectively to break down phenylalanine. It is not effective for all individuals with PKU.
Palynziq (pegvaliase-pqvz): An enzyme substitution therapy approved for adults with PKU whose blood phenylalanine levels remain too high even with dietary management. It's an injectable medication that breaks down phenylalanine.
Is Communicable
No, PKU is not communicable. It is a genetic disorder and cannot be spread from person to person.
Precautions
Strict adherence to a low-phenylalanine diet: This is crucial for managing PKU and preventing complications.
Regular monitoring of phenylalanine levels: Frequent blood tests are necessary to ensure that phenylalanine levels are within the target range.
Genetic counseling: Families with a history of PKU should consider genetic counseling to understand the risk of having a child with the disorder.
Special attention during pregnancy: Women with PKU need to carefully manage their phenylalanine levels before and during pregnancy to prevent harm to the developing fetus.
Consultation with a metabolic specialist and registered dietitian: These healthcare professionals can provide guidance on dietary management and other aspects of PKU care.
How long does an outbreak last?
PKU is not an "outbreak" type of illness. It is a chronic, lifelong condition. If untreated, the symptoms and complications persist throughout life. With consistent management, the goal is to prevent or minimize the development of these complications.
How is it diagnosed?
Newborn screening: PKU is typically diagnosed through newborn screening, which involves a blood test done shortly after birth. This test measures the level of phenylalanine in the blood.
Confirmatory testing: If the newborn screening test is positive, further blood tests are done to confirm the diagnosis and determine the severity of the condition.
Genetic testing: Genetic testing can identify mutations in the PAH gene, which confirms the diagnosis and can help predict the severity of the disease.
Timeline of Symptoms
9. Timeline of symptoms
Newborn period: Infants with PKU usually appear normal at birth.
Within a few months: If untreated, phenylalanine levels begin to rise, and symptoms may start to appear, such as a musty odor, feeding difficulties, and irritability.
Later infancy and childhood: As phenylalanine continues to accumulate, developmental delays, seizures, and other neurological problems can develop.
Long-term: Untreated PKU can lead to severe intellectual disability, behavioral problems, and other chronic health issues.
Important Considerations
Early diagnosis and treatment are essential to prevent the long-term complications of PKU.
Dietary management is a lifelong commitment.
Individuals with PKU require ongoing monitoring and care from a team of healthcare professionals.
Even with treatment, some individuals may experience challenges with executive function, attention, and mood.
Support groups and resources are available to help individuals with PKU and their families.