Amino Acid Disorders Flashcards
The most well known of the aminoacidurias
Phenylketonuria
estimated to occur in 1 of every 10,000 to 20,000 births
Phenylketonuria
if undetected, results in severe mental retardation
Phenylketonuria
first identified in Norway by Ivan Følling in 1934, when a
mother with other mentally retarded children reported a
peculiar mousy odor to her child’s urine
Phenylketonuria
mousy odor in urine
Phenylketonuria
increased amounts of keto acids including phenylpyruvate
Phenylketonuria
normal conversion of phenylalanine to tyrosine is disrupted
Phenylketonuria
Interruption of the pathway also produces children with fair complexions—even in dark-skinned families—owing to the decreased production of tyrosine and its pigmentation metabolite melanin
Phenylketonuria
caused by failure to inherit the gene to produce the enzyme phenylalanine hydroxylase
Phenylketonuria or PKU
The gene is inherited as an autosomal recessive trait with
no noticeable characteristics or defects exhibited by heterozygous carriers
Phenylalanine hydroxylase
major constituent of milk and contained large amounts in aspartame
phenylalanine
Initial screening for PKU goes undetected in the urinalysis lab as the increased blood levels of phenylalanine must occur before urinary excretion of phenylpyruvic acid
2-6 weeks
In PKU, blood is collected
24 hours after birth
Phenylalanine can be detected as early as
4 hours after birth, and if cutoff values are lowered from 4 mg/dL to 2 mg/dL
BOY or GIRL: escape detection of PKU during early tests because of slower rises in blood phenylalanine levels
Girl
Newborn Screening Act of 2004
RA 9288
RA 9288 offers
expanded NBS will be offered as OPTIONAL to parents in all participating facilities
550 pesos for the initial 6 test
1500 pesos for the full complement of disorder
currently being used in screening for inherited disorders in newborns and has the ability to detect more than 25 different genetic disorders with a single specimen. This method is replacing the multiple procedures currently used in newborn screening programs
Tandem Mass Spectrometry (MS/MS)
reference method for quantitative serum phenylalanine
High Performance Liquid Chromatography (HPLC)
urine testing using ferric chloride may be used as a follow-up test to ensure proper dietary control in previously diagnosed cases and as a means of monitoring the dietary intake of pregnant women known to lack phenylalanine hydroxylase (5 drops of 10% ferric chloride to urine containing phenylpyruvic acid produces BLUE-GREEN COLOR)
FeCl3 Tube Test
a semiquantitative, bacterial inhibition assay for phenylalanine
that uses the ability of phenylalanine to facilitate bacterial growth(Bacilus subtilis) in a culture medium with an inhibitor (ꞵ-2-thienylalanine)
+ for Phenylketonuria = GROWTH
Guthrie test
provide false negative results due to the infant not being at least 24 hours old, which ensures adequate time for enzyme and amino acid levels to develop, and due to the sample not being taken before the administration of antibiotics or transfusion of blood or blood products
Guthrie Test
Treatment of PKU
High-protein foods, such as meat, fish, poultry, eggs, cheese, and milk, are avoided.
calculated amounts of cereals, starches,
fruits, and vegetables, along with a milk
substitute, are usually recommended
first drug to help manage PKU
The drug helps reduce
phenylalanine levels by increasing the activity of the PAH enzyme
Kuvan (sapropterin dihydrochloride)
