Aminoacidopathies Clinical Chemistry Review 88
DISEASE CAUSE EFFECT DIAGNOSIS
Phenylketonuria
Tyrosinemia
Alkaptonuria
Maple syrup urine
disease (MSUD)
Homocystinuria
Cystinuria
Deficiency of enzyme that converts
phenylalanine to tyrosine. Phenylpyruvic
acid in blood & urine.
Disorder of tyrosine catabolism.
Tyrosine & its metabolites are
excreted in urine.
Deficiency of enzyme needed in
metabolism of tyrosine & phenylalanine.
Buildup of homogentisic acid.
Enzyme deficiency leading to buildup of
leucine, isoleucine, valine.
Deficiency in enzyme needed for metabo-
lism of methionine. Methionine &
homocysteine build up in plasma & urine.
Increased excretion of cystine due to
defect in renal reabsorption.
Mental retardation. Urine has
“mousy” odor.
Liver & kidney disease, death.
Diapers stain black due to homogen-
tisic acid in urine. Later in life, dark-
ening of tissues, hip & back pain.
Burnt-sugar odor to urine, breath,
skin. Failure to thrive, mental retarda-
tion, acidosis, seizures, coma, death.
Osteoporosis, dislocated lenses in
eye, mental retardation, throm-
boembolic events.
Recurring kidney stones.
Guthrie bacterial inhibition
assay, HPLC, tandem mass
spectrometry (MS/MS), fluoro-
metric & enzymatic methods.
All newborns are screened
MS/MS
Gas chromatography & mass
spectroscopy
Modified Guthrie test, MS/MS
Guthrie test, MS/MS, LC-MS/MS
Test urine with cyanide nitro-
prusside. Pos = red-purple color
