Phenylketonuria (PKU) is an autosomal recessive genetic disorder that impairs the synthesis and function of the protein phenylalanine hydroxylase (PAH). PAH is a protein-based enzyme that catalyzes the change of phenylalanine to tyrosine. PKU is also known by aliases such as hyperphenylalaninemia, phenylalanine hydroxylase deficiency disease, and Folling's disease. PKU's name derived from ketonuria, the urination of ketones. In untreated PKU, phenylalanine is urinated.
Since PKU is an autosomal recessive disorder, an individual must inherit two defective copies of the PAH gene to be afflicted with PKU. The PAH gene is located on the long arm of chromosome 12 between positions 22 and 24.2 ( or base pairs 102,838,320 to 102,917,602). Over 500 different mutations in the PAH gene have been linked to phenylketonuria, but the most common mutation is the substitution of arginine with tryptophan at position 408 in the gene. The symptoms of PKU are caused by a double whammy: excessive phenylalanine is toxic to the nervous system and a lack of tyrosine reduces the production of certain proteins, melanin, and neurotransmitters.
The symptoms of PKU can range from merely annoying to debilitating. There are two main forms of PKU, classic and variant/non-PKU. Classic PKU is the severe form, where PAH function is absent or almost absent. Variant/non-PKU is the range of other mutations that only partially damage the protein, with some forms so mild that treatment is not required. Symptoms of PKU include permanent brain damage, seizures, psychiatric disorders, delayed mental development, hypopigmentation (whitening of skin and hair), urination of phenylalanine, a mousy/musty odor, and in some cases, death. The standard diagnosis is a blood test at birth. If it comes back with high phenylalanine levels, further work such as DNA, blood, and urine tests are conducted.
There is no cure for PKU and there is little for medication. The current and most common treatment is a low phenylalanine diet. This diet restricts high-protein foods such as dairy products, eggs, meat, beans, nuts, soy, and the artificial sweetener aspartame. The foods allowed by the diet are fruits, vegetables, and low-protein grains. Due to the low protein obtained in the diet, a specialized formula, such as Lofenalac, is given to supply the body with low-phenylalanine proteins. One pharmaceutical drug called Kuvan may be prescribed to help lower phenylalanine levels.
Various support groups founded by people infected with PKU and their families have made an effort to increase research towards effective treatments and cures. One of the largest of these support groups is the National PKU Alliance. The NPKUA focuses on collecting and disturbing funds for research, care for those with PKU, and spreading awareness of PKU. Potential new treatments for PKU include gene therapy, enzyme substitution therapy, and large neutral amino acid supplementation.
Works Cited
Since PKU is an autosomal recessive disorder, an individual must inherit two defective copies of the PAH gene to be afflicted with PKU. The PAH gene is located on the long arm of chromosome 12 between positions 22 and 24.2 ( or base pairs 102,838,320 to 102,917,602). Over 500 different mutations in the PAH gene have been linked to phenylketonuria, but the most common mutation is the substitution of arginine with tryptophan at position 408 in the gene. The symptoms of PKU are caused by a double whammy: excessive phenylalanine is toxic to the nervous system and a lack of tyrosine reduces the production of certain proteins, melanin, and neurotransmitters.
The symptoms of PKU can range from merely annoying to debilitating. There are two main forms of PKU, classic and variant/non-PKU. Classic PKU is the severe form, where PAH function is absent or almost absent. Variant/non-PKU is the range of other mutations that only partially damage the protein, with some forms so mild that treatment is not required. Symptoms of PKU include permanent brain damage, seizures, psychiatric disorders, delayed mental development, hypopigmentation (whitening of skin and hair), urination of phenylalanine, a mousy/musty odor, and in some cases, death. The standard diagnosis is a blood test at birth. If it comes back with high phenylalanine levels, further work such as DNA, blood, and urine tests are conducted.
There is no cure for PKU and there is little for medication. The current and most common treatment is a low phenylalanine diet. This diet restricts high-protein foods such as dairy products, eggs, meat, beans, nuts, soy, and the artificial sweetener aspartame. The foods allowed by the diet are fruits, vegetables, and low-protein grains. Due to the low protein obtained in the diet, a specialized formula, such as Lofenalac, is given to supply the body with low-phenylalanine proteins. One pharmaceutical drug called Kuvan may be prescribed to help lower phenylalanine levels.
Various support groups founded by people infected with PKU and their families have made an effort to increase research towards effective treatments and cures. One of the largest of these support groups is the National PKU Alliance. The NPKUA focuses on collecting and disturbing funds for research, care for those with PKU, and spreading awareness of PKU. Potential new treatments for PKU include gene therapy, enzyme substitution therapy, and large neutral amino acid supplementation.
Works Cited
"PAH
Gene." Genetics Home Reference. N.p., n.d. Web.
20 Apr. 2015.
"What
Are Common Treatments for Phenylketonuria (PKU)?" What
Are Common Treatments for Phenylketonuria (PKU)?N.p., n.d. Web. 20 Apr. 2015.
"National PKU Alliance." National
PKU Alliance.
N.p.,
n.d.
Web. 20 Apr. 2015.
"Phenylketonuria."
Genetics
Home Reference.
N.p., n.d. Web.
20 Apr. 2015.
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