Phenylketonuria: Difference between revisions

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{{SI}}
{{Infobox medical condition
{{Infobox medical condition
| name         = Phenylketonuria
| name = Phenylketonuria
| synonyms      = PKU
| image = [[File:L-Phenylalanin_-_L-Phenylalanine.svg|thumb|alt=Chemical structure of phenylalanine]]
| image        =  
| caption = Chemical structure of [[phenylalanine]]
| caption      =  
| synonyms = PKU
| pronounce     =  
| pronounce =
| specialty     = [[Genetics]], [[Pediatrics]]
| specialty = [[Medical genetics]]
| symptoms     = Intellectual disability, seizures, behavioral problems, mental disorders
| symptoms = Intellectual disability, seizures, behavioral problems, mental disorders, musty smell
| complications =
| onset = Symptoms develop gradually
| onset         = Early infancy
| duration = Lifelong
| duration     = Lifelong
| causes = [[Genetic mutation]] in the [[PAH (gene)|PAH gene]]
| types        =
| risks = Family history
| causes       = Genetic ([[autosomal recessive inheritance]])
| diagnosis = [[Newborn screening]], [[blood test]]
| risks         = Family history
| differential = [[Hyperphenylalaninemia]], [[biopterin deficiency]]
| diagnosis     = Newborn screening ([[blood test]])
| prevention = [[Dietary management]]
| differential =  
| treatment = [[Low-phenylalanine diet]], [[sapropterin]]
| prevention   =  
| medication = [[Sapropterin]], [[pegvaliase]]
| treatment     = Low-phenylalanine diet, [[Amino acid]] supplements
| prognosis = Good with treatment
| medication   = Sapropterin
| frequency = 1 in 12,000 births
| prognosis     = Good with early treatment
| deaths = Rare with treatment
| frequency     = 1 in 10,000 to 15,000 newborns in the United States
| deaths       =  
}}
}}
 
[[File:Inborn_errors_of_metabolism_of_phenylalanine_and_tyrosine.svg|thumb|Metabolic pathway of phenylalanine and tyrosine]]
'''Phenylketonuria''' ('''PKU''') is a genetic disorder characterized by an inability in the body to metabolize the [[amino acid]] phenylalanine. Due to a deficiency in the enzyme phenylalanine hydroxylase, individuals with PKU accumulate high levels of phenylalanine in their blood, which can lead to various health problems including intellectual disability, seizures, and other serious medical issues.
'''Phenylketonuria''' ('''PKU''') is a rare [[genetic disorder]] characterized by the inability to metabolize the amino acid [[phenylalanine]]. This condition is caused by a deficiency in the enzyme [[phenylalanine hydroxylase]], which is necessary for converting phenylalanine to [[tyrosine]].
 
== Genetics ==
==Causes==
PKU is inherited in an [[autosomal recessive]] pattern, meaning that an individual must inherit two copies of the defective gene, one from each parent, to be affected by the disorder. The gene responsible for PKU is located on chromosome 12.
PKU is caused by mutations in the PAH gene, which encodes the enzyme phenylalanine hydroxylase. This enzyme is crucial for the normal metabolism of phenylalanine, a building block of proteins. The mutations lead to reduced activity or complete absence of this enzyme, resulting in the accumulation of phenylalanine. PKU is inherited in an [[autosomal recessive]] pattern, meaning that an individual must inherit two copies of the mutated gene, one from each parent, to be affected.
== Pathophysiology ==
 
In individuals with PKU, the accumulation of phenylalanine in the body can lead to a variety of health problems. High levels of phenylalanine can cause damage to the [[brain]] and [[nervous system]], leading to intellectual disability and other neurological issues.
==Symptoms==
== Clinical Features ==
The primary symptoms of PKU include:
[[File:NIH_microcephaly.jpg|left|thumb|Microcephaly is a possible feature of untreated PKU]]
* Intellectual disability
Symptoms of PKU can vary but often include intellectual disability, [[microcephaly]], [[seizures]], and behavioral problems. If untreated, PKU can lead to severe developmental delays and neurological complications.
* Seizures
== Diagnosis ==
* Delayed development
[[File:Phenylketonuria_testing.jpg|left|thumb|Newborn screening for PKU]]
* Behavioral problems
PKU is typically diagnosed through [[newborn screening]] programs, which test for elevated levels of phenylalanine in the blood. Early detection is crucial for preventing the adverse effects of the disorder.
* Psychiatric disorders
== Treatment ==
* Skin rashes (eczema)
The primary treatment for PKU is a [[phenylalanine-restricted diet]], which involves limiting the intake of foods high in phenylalanine, such as meat, dairy, and nuts. Special medical formulas and foods are often used to ensure adequate nutrition while maintaining low phenylalanine levels.
 
== Complications ==
If the disorder is not diagnosed early, and dietary management is not initiated, the buildup of phenylalanine can impair brain development leading to progressive intellectual disability and other neurological issues.
If PKU is not managed properly, individuals may experience severe intellectual disability, behavioral problems, and other neurological issues. Pregnant women with PKU must maintain strict control of their phenylalanine levels to prevent [[maternal PKU syndrome]], which can affect the developing fetus.
 
== Prevention ==
==Diagnosis==
[[File:Phenylalanine_warning_for_phenylketonurics.jpg|left|thumb|Warning label for phenylketonurics]]
PKU is commonly diagnosed through newborn screening, which involves a simple [[blood test]] to measure phenylalanine levels. This test is typically performed within a few days of birth. Early diagnosis and treatment are crucial to prevent the symptoms and complications associated with PKU.
Genetic counseling is recommended for families with a history of PKU. Prenatal testing and carrier screening can help identify at-risk pregnancies and individuals.
 
== See also ==
==Treatment==
* [[Inborn errors of metabolism]]
The main treatment for PKU involves a diet low in phenylalanine, which necessitates strict dietary management to limit the intake of foods high in this amino acid, such as meat, fish, eggs, and dairy products. Special low-phenylalanine formulas and foods are used to support normal growth and development in children.
* [[Amino acid metabolism]]
 
* [[Genetic disorders]]]]
Additionally, some individuals may benefit from the drug sapropterin (a synthetic form of tetrahydrobiopterin or BH4), which can increase the tolerance to phenylalanine in some cases. Regular monitoring of phenylalanine levels in the blood is necessary to adjust dietary intake and ensure optimal management.
== See Also ==
 
* [[Tyrosinemia]]
==Prognosis==
* [[Alkaptonuria]]
With early and consistent treatment, individuals with PKU can lead healthy lives with normal intelligence. Ongoing research continues to explore new treatments and potential cures, including gene therapy.
* [[Maple syrup urine disease]]
 
==Epidemiology==
The incidence of PKU varies globally, but it is estimated to affect approximately 1 in 10,000 to 15,000 newborns in the United States. It is more common in certain populations, such as those of European descent.
 
[[Category:Genetic disorders]]
[[Category:Genetic disorders]]
[[Category:Metabolic disorders]]
[[Category:Metabolic disorders]]
[[Category:Inborn errors of metabolism]]
[[Category:Autosomal recessive disorders]]
{{medicine-stub}}
<gallery>
File:L-Phenylalanin - L-Phenylalanine.svg|L-Phenylalanine
File:NIH microcephaly.jpg|Microcephaly
File:autorecessive.svg|Autosomal Recessive Inheritance
File:Clinical|Clinical Presentation
File:Inborn errors of metabolism of phenylalanine and tyrosine.svg|Inborn Errors of Metabolism
File:Phenylketonuria testing.jpg|Phenylketonuria Testing
File:Phenylalanine warning for phenylketonurics.jpg|Phenylalanine Warning for Phenylketonurics
</gallery>

Latest revision as of 04:26, 14 April 2025

Editor-In-Chief: Prab R Tumpati, MD
Obesity, Sleep & Internal medicine
Founder, WikiMD Wellnesspedia &
W8MD's medical weight loss NYC, sleep center NYC
Philadelphia medical weight loss and Philadelphia sleep clinics

Phenylketonuria
Chemical structure of phenylalanine
Synonyms PKU
Pronounce
Specialty Medical genetics
Symptoms Intellectual disability, seizures, behavioral problems, mental disorders, musty smell
Complications N/A
Onset Symptoms develop gradually
Duration Lifelong
Types N/A
Causes Genetic mutation in the PAH gene
Risks Family history
Diagnosis Newborn screening, blood test
Differential diagnosis Hyperphenylalaninemia, biopterin deficiency
Prevention Dietary management
Treatment Low-phenylalanine diet, sapropterin
Medication Sapropterin, pegvaliase
Prognosis Good with treatment
Frequency 1 in 12,000 births
Deaths Rare with treatment


Metabolic pathway of phenylalanine and tyrosine

Phenylketonuria (PKU) is a rare genetic disorder characterized by the inability to metabolize the amino acid phenylalanine. This condition is caused by a deficiency in the enzyme phenylalanine hydroxylase, which is necessary for converting phenylalanine to tyrosine.

Genetics[edit]

PKU is inherited in an autosomal recessive pattern, meaning that an individual must inherit two copies of the defective gene, one from each parent, to be affected by the disorder. The gene responsible for PKU is located on chromosome 12.

Pathophysiology[edit]

In individuals with PKU, the accumulation of phenylalanine in the body can lead to a variety of health problems. High levels of phenylalanine can cause damage to the brain and nervous system, leading to intellectual disability and other neurological issues.

Clinical Features[edit]

Microcephaly is a possible feature of untreated PKU

Symptoms of PKU can vary but often include intellectual disability, microcephaly, seizures, and behavioral problems. If untreated, PKU can lead to severe developmental delays and neurological complications.

Diagnosis[edit]

Newborn screening for PKU

PKU is typically diagnosed through newborn screening programs, which test for elevated levels of phenylalanine in the blood. Early detection is crucial for preventing the adverse effects of the disorder.

Treatment[edit]

The primary treatment for PKU is a phenylalanine-restricted diet, which involves limiting the intake of foods high in phenylalanine, such as meat, dairy, and nuts. Special medical formulas and foods are often used to ensure adequate nutrition while maintaining low phenylalanine levels.

Complications[edit]

If PKU is not managed properly, individuals may experience severe intellectual disability, behavioral problems, and other neurological issues. Pregnant women with PKU must maintain strict control of their phenylalanine levels to prevent maternal PKU syndrome, which can affect the developing fetus.

Prevention[edit]

Warning label for phenylketonurics

Genetic counseling is recommended for families with a history of PKU. Prenatal testing and carrier screening can help identify at-risk pregnancies and individuals.

See also[edit]

See Also[edit]