Phenylketonuria (NORD)
00:00 / 00:00
Videos
Notes
Phenylketonuria (NORD)
Information for patients and families
Glut1 Deficiency Foundation
Glut1 deficiency syndrome (Glut1 Deficiency Foundation)
Gorlin Syndrome Alliance
Gorlin syndrome (Gorlin Syndrome Alliance)
The National Organization for Rare Disorders (NORD)
Recurrent pericarditis (NORD)
Autoimmune polyglandular syndrome type 1 (NORD)
Opsoclonus myoclonus syndrome (NORD)
Thyroid eye disease (NORD)
Bile synthesis disorders (NORD)
Cyclic vomiting syndrome (NORD)
Eosinophilic esophagitis (NORD)
Short bowel syndrome (NORD)
Essential thrombocythemia (NORD)
Myelofibrosis (NORD)
Polycythemia vera (NORD)
Sickle cell disease (NORD)
Waldenstrom macroglobulinemia (NORD)
Warm autoimmune hemolytic anemia and cold agglutinin (NORD)
Congenital athymia (NORD)
Cytomegalovirus infection after transplant (NORD)
Post-transplant lymphoproliferative disorders (NORD)
Severe chronic neutropenia (NORD)
Adrenoleukodystrophy (NORD)
Alagille syndrome (NORD)
Aromatic L-amino acid decarboxylase deficiency (NORD)
Cerebrotendinous xanthomatosis (NORD)
Classical homocystinuria (NORD)
Congenital cytomegalovirus (NORD)
Cystinuria (NORD)
Fabry disease (NORD)
Gaucher disease (NORD)
Glycogen storage disease type II (NORD)
Metachromatic leukodystrophy (NORD)
Mucopolysaccharide storage disease type 1 (Hurler syndrome) (NORD)
Mucopolysaccharide storage disease type 2 (Hunter syndrome) (NORD)
Mycobacterium avium complex (NORD)
NGLY1 deficiency (NORD)
Niemann-Pick disease types A and B (NORD)
Phenylketonuria (NORD)
PIK3CA-related overgrowth spectrum (NORD)
Tay-Sachs disease (NORD)
Zellweger spectrum disorders (NORD)
Early infantile epileptic encephalopathy (NORD)
Opsoclonus myoclonus syndrome (NORD)
Spinocerebellar ataxia (NORD)
Narcolepsy (NORD)
Focal segmental glomerulosclerosis (NORD)
IgA nephropathy (NORD)
Pulmonary arterial hypertension (NORD)
The Primary School
ADHD: Information for patients and families (The Primary School)
Asthma: Information for patients and families (The Primary School)
Childhood nutrition and obesity: Information for patients and families (The Primary School)
Childhood oral health: Information for patients and families (The Primary School)
Food allergies and EpiPens: Information for patients and families (The Primary School)
Toxic stress: Information for patients and families (The Primary School)
Assessments
Phenylketonuria (NORD)
Flashcards
0 / 12 complete
USMLE® Step 1 questions
0 / 4 complete
High Yield Notes
7 pages
Flashcards
Phenylketonuria (NORD)
of complete
Questions
USMLE® Step 1 style questions USMLE
of complete
External References
First Aid
2022
2021
2020
2019
2018
2017
2016
Cofactors
phenylketonuria p. 81
Congenital heart disease p. 304-306
maternal phenylketonuria p. 82
Eczema
phenylketonuria p. 82
Microcephaly
maternal phenylketonuria p. 82
Phenylketonuria p. 82, 82
Pregnancy p. 657
maternal phenylketonuria p. 81
Seizures p. 535
phenylketonuria p. 82
Transcript
Content Reviewers
Phenylketonuria or PKU is a rare metabolic disease that can lead to severe brain disorders caused by the accumulation of the amino acid phenylalanine to toxic levels in the blood and brain.
Amino acids are the basic building blocks that make up proteins. Phenylalanine, or Phe, is one of the essential amino acids. It is necessary for life, but our bodies can't make it; therefore, Phe must be acquired through foods that contain protein. Normally, once Phe enters the body, most of it is converted to tyrosine by the enzyme phenylalanine hydroxylase. Tyrosine is then turned into neurotransmitters important for normal brain development and function.
PKU is an autosomal recessive genetic disorder that affects function of the phenylalanine hydroxylase enzyme. The phenylalanine hydroxylase gene is located on chromosome 12 and over 600 mutations have been described. The degree of enzyme function can vary. When untreated, people with PKU develop symptoms such as severe intellectual disability, psychiatric disorders, and seizures. A pregnant woman with PKU must pay special attention to her Phe levels to reduce the risk of Maternal PKU Syndrome that can result in heart defects, microcephaly, and developmental disability in her baby.
In PKU, elevated Phe levels and reduced tyrosine levels can change the way the brain functions. This is because Phe uses the same transporters to get across the blood-brain barrier as other amino acids including- tyrosine and tryptophan. Tyrosine is needed to synthesize dopamine and norepinephrine, and tryptophan is needed to synthesize the neurotransmitter serotonin. As Phe levels rise, it occupies all the transporters, making it hard for tyrosine and tryptophan to get across the blood-brain barrier. As a result, dopamine, norepinephrine, and serotonin levels in the brain begin to fall, leading to abnormal brain development and intellectual disability.
Summary
Phenylketonuria (PKU) is an autosomal recessive amino acid metabolism disorder involving impaired metabolism of the amino acid phenylalanine, caused by the absence or reduced activity of phenylalanine hydroxylase. In PKU toxic levels of phenylalanine and phenylketone build up in the body and tyrosine levels drop.
Symptoms include a musty odor of sweat and urine, intellectual disability, seizures, behavioral problems, and other neurological symptoms. In pregnant females, PKU can affect the fetus - causing heart disease, growth problems, intellectual disability, and microcephaly. Treatment is based on a diet with low levels of phenylalanine and supplementing with tyrosine and tetrahydrobiopterin.
For Institutions
Copyright © 2023 Elsevier, its licensors, and contributors. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Cookies are used by this site.
USMLE® is a joint program of the Federation of State Medical Boards (FSMB) and the National Board of Medical Examiners (NBME). COMLEX-USA® is a registered trademark of The National Board of Osteopathic Medical Examiners, Inc. NCLEX-RN® is a registered trademark of the National Council of State Boards of Nursing, Inc. Test names and other trademarks are the property of the respective trademark holders. None of the trademark holders are endorsed by nor affiliated with Osmosis or this website.
