Urine Screening for Metabolic Disorders
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Transcript of Urine Screening for Metabolic Disorders
Urine Screening for Metabolic DisordersAng. Avena. Blas. Tagarao. 3FMT
Metabolic Substances in the
Urine Overflow Type
- disruption of normal metabolic pathway
- increase in plasma concentrations from the non-metabolized substances.
Renal Type
- abnormal accumulations of substances that are caused by malfunctions in the mechanism of tubular reabsorption
Amino Acid Disorders
• Phenylalanine-Tryptophan Disorders• Branched Chain Amino Acid Disorders• Cysteine and Homocysteine Disorders• Porphyrin Disorders• Mucopolysaccharide Disorders• Purine Disorders• Carbohydrate Disorders
Phenylalanine-Tryptophan Disorders
• Phenylketonuria • Tyroslyuria• Melanuria• Alkaptonuria
Phenylketonuria (PKU)
Inherited autosomal recessive trait
absence of activity of the enzyme phenylalanine hydroxylase (PAH)
catalyzes the conversion of phenylalanine to tyrosine
Catabolites: phenylpyruvic acid, phenyllactic acid, phenylacetic acid, phenylacetylglutamine
Types: Mild PKU (600-1200 μmol/L) Non-PKU mild hyperphenylalaninenemia (180-600 μmol/L; no
phenylketones)
Can cause:Mental retardationsConvulsionsBehavior problems Skin rashMusty body odor
Urine: Musty Odor
Test: Ferric Chloride Tube Test
Procedure: 5 drops 10% FeCl3 + 1mL urine sample
FeCl3 reacts w/ phenylpyruvic acid = Permanent blue-green color.
Tyrosyluria
accumulation of excess tyrosine in the plasma (tyrosinemia)
either inherited or metabolic defect
Urine: excess tyrosine or , p-hydroxyphenylpyruvic acid and p-hydroxy phenyllatic acid.
Three types of Tyrosinemia:
1) Type I – low levels of the enzyme fumarylacetoacetate hydrolase, the last of five enzymes needed to break down tyrosine
2) Type II –a deficiency of the enzyme tyrosine aminotransferase, the first in a series of five enzymes that converts tyrosine to smaller molecules
3) Type III – deficiency of the enzyme 4-hydroxyphenylpyruvate dioxygenase, ncluded in the five enzymes needed to break down tyrosine
Test: Nitroso-Napthol Test
Procudure:
1mL of 2.63N nitric acid + 1 drop of 21.5% sodium nitrite + 0.1mL 1-nitroso-2-napthol + 5 drops of urine
Mix and wait for 5 minutes
Result: Orange-red color which indicates tyrosine metabolites
Melanuria Darkening of the urine = increase of melanin in
the body
Melanin - is the pigment responsible for the dark color of hair, skin and eyes.
Serious finding: if urinary melanin is elevated - indicates proliferation of the normal melanin-producing cells (melanocytes)
Urine: Dark urine
5,6-dihydoxyindole - a colorless precursor of melanin
secreted by Malignant melanoma oxidizes to melanogen melanin
Alkaptonuria Inborn metabolic disease transmitted as an autosomal
recessive gene
HDG gene - the lack of the enzyme homogentisate oxidase (needed in the metabolism of tyrosine and phenylalanine)
Test: Homogentisic Acid Test
Procedure:
0.5 mL of urine + 4 mL of 3% silver nitrite and mix
Result: Black color after 24 hours
Other tests
Ferric Chloride Test: transient deep blue color
Clinitest: Yellow precipitate
Branched Chain Amino Acid Disorders
• Maple Syrup Urine Disorders• Organic Acidemia • Indicanuria• 5-Hydoxyindolacetic Acid
Maple Syrup Urine Disorders (MSUD)
rare autosomal recessive genetic inherited disorder
absence or reduced activity of the enzyme branched-chain-α-ketoacid decarboxylase
blocking the normal metabolism of the three essential branched-chain amino acids leucine, isoleucine and valine.
1:150,000 births
Urine: Maple syrup or burnt sugar odor
Test: 2,4-Dinitrophenylhydrazine (DNPH) Test
Procedure
10 drops of 0,2% 2,4-DNPH + 2N HCL +1 mL urine
Wait for 10 minutes
Result: Yellow turbidity and precipitate.
Organic Acidemia
Three most frequently encountered disorders:
Isovaleric
Propionic
Methylmalonic
The presence of these three can be detected by newborn screening programs using MS/MS.
Isovaleric academia autosomal recessive metabolic disorder from a
deficiency of the enzyme isovaleryl-CoA dehydrogenase
preventing normal metabolism of the amino acid leucine.
1:250,000 births
Urine: Sweaty feet odor urine
Propionic and Methylmalonic Acidemia
due from the errors in the metabolic pathway converting isoleucine, valine and threonine and methionine to succinyl CoA.
Indicanuria Due to certain intestinal disorders, presence of
abnormal bacteria, malabsorption syndrome
Hartnup disease - increase amounts of tryptophan are converted to indole
Excess indole is then reabsorbed from the intestine into the bloodstream and circulated to the liver, converted to indican and then excreted in the urine.
Urine: Colorless
Urine exposed to air: oxidized to Indigo Blue.
5-Hydoxyindolacetic Acid (5-HIAA)
The degradation product of serotonin that is excreted in the urine normally in small amounts.
Serotonin - produced from the second metabolic pathway of tryptophan by the argentaffin cells in the intestine.
If there are carcinoid tumors involving the argentaffin cells develop = increase in the production of serotonin results in the elevation of urinary 5-HIAA levels.
Cysteine and Homocysteine
Disorders
• Cystinuria• Cystinosis• Homocystinuria
Cystinuria
inherited renal tubular disorder.
Two forms:
1. patients cannot reabsorb lysine, ornithine, arginine, or cysteine
2. only cysteine and lysine cannot be reabsorbed.
more likely to have pathological urinary cysteine crystals and stones composed of cysteine.
Cystine forms urinary calculi (insoluble, unless alkalinize)
Test: Cyanide nitroprusside test
Result: Red Purple Color
Treatment: More water intake (4L/day)PenicillinasePercutaneous nephrolithotripsy
Cystinosis
Inborn Errors of Metabolism (IEM) – can range from from severe and fatal in infancy to a milder adult form.
defect in the lysosomal membrane
prevents release of cystine into the cellular cytoplasm for metabolism
Leads to: Deposition of cysteine crystals in many cells of the body.
Patients w/Fanconi syndrome deposits of cysteine in the cells of the proximal convoluted tubule interfere with reabsorption and of these crystal deposits in cells can lead to early renal failure.
Mild Form: No kidney involvement
polyuria and positive urine tests for reducing substances
Urinalysis tests = lack of ability to vary specific gravity.
Test: cyanide nitroprusside test
Result: Positive
Homocystinuria Lack of the enzyme cystathionine β-synthase
necessary for the metabolism of the amino acid methionine
increased plasma and urine levels of methionine and of the precursor homocysteine.
Result to: failure to thrive mental retardation Cataractsincreased thrombosis riskDeath
Prevention: Diet modification with reduction in methionine
sourceshigh doses of Vitamin B6
Test: Cyanide nitroprusside test
Result: Positive
Other test:Silver Nitroprusside test – needed to differentiate
from the cystine disorders.
Homocystinuria = postive
Cystinuria = negative
Cystinosis = negative
Porphyrin Disorders
• Porphyrins – complex iron-fee cyclic substances; intermediates in the biosynthetic pathway of heme.
• Porphyrins differ in the side chains present at the eight available positions on the pyrrole rings.
• Major sites for Porphyrin production are:1. bone marrow - intermediates in the synthesis of
hemoglobin2. liver and other tissues - produce intermediates for
other heme proteins like myoglobin.
Porphyrins can be seen elevated in: urine, feces, and/or blood
Porphobilinogen (PBG) and the porphyrinogens -colorless, non-fluorescent substances
Oxidized forms or the Porphyrins have red pigments under the microscope
Urine: port wine / burgundy color
Common method for separating individual porphyrin: high performance liquid chromatography
Delta-aminolevulenic Acid Dehydrogenase Deficiency Porphyria Delta-aminolevulinic acid dehydratase (ALAD),
also known as porphobilinogen synthase, catalyzes the second step of heme synthesis. Deficiency of this enzyme produces ALAD deficiency porphyria (ADP), an extremely rare cause of acute porphyria.
a rare form of acute porphyria
aminolevulenic acid is increased
PBG is not increased
Acute porphyriasrapid testing is important.
Porphobilinogen is increased patients with symptoms of acute porphyrias
PBG testing is both sensitive and specific
Measurement of PBG is often combined with measurments for delta aminolevulenic acid and total urine porphyrins.
Cutaneous Porphyria
measuring total plasma Porphyrins is effective for screening patients with skin photosensitivity
Plasma Porphyrins are rarely increased in other medical conditions.
Mucopolysaccharide Disorders
• Mucopolysaccharidoses Hurler Syndrome Hunter Syndrome Sanfilippo Syndrome
Mucopolysaccharidesaka Glycosaminoglycans
group of large compounds located primarily in connective tissue (CT)
consists of a protein core with numerous polysaccharide branches
products most frequently found in urine are dermatan sulfate, keratan sulfate, and heparan sulfate
Mucopolysaccharidoses
inherited disorders in the metabolism of mucopolysaccharides
preventing complete breakdown of polysaccharide portion
accumulation of incompletely metabolized polysaccharide portion in lysosomes of CT cells
increased excretion in urine
Types
1. Hurler Syndrome
abnormal skeletal structure
severe mental retardation
mucopolysaccharides accumulate in the cornea of the eye
2. Hunter Syndrome
abnormal skeletal structure
severe mental retardation
sex-linked recessive (rarely seen in females)
3. Sanfilippo Syndrome
mental retardation
Diagnosis: Urinary screening test – newborn
1. acid-albumin and CTAB turbidity test
2. metachromatic staining spot test
Result: white turbidity (+)
Purine Disorders• Lesch-Nyhan Disease
Carbohydrate Disorders
• Melituria
Lesch-Nyhan Syndrome inherited, sex-linked recessive
massive excretion of urinary uric acid crystals
severe motor defects
mental retardation
tendency towards self-destruction, gout, and renal calculi
Diagnosis
normal development for the first 6-8 months
First Sign: uric acid crystals in diaper resembling orange sand
Increased uric acid crystals in pediatric urine specimen
Melituria
increased urinary sugar
usually caused by an inherited disorder
Most cause no disturbance in body metabolism
Type:
1. Pentosuria
2. Galactosuria
3. Lactosuria
4. Fructosuria
Pentosuria presence of pentose sugars in urine
one of Garrod’s original six IEMs
ingestion of large amounts of fruit
Galactosuria inability to properly metabolize galactose to
glucose
deficiency in any of the enzymes:
1. galactose-1-phosphate uridyl transferase (GALT) - causes severe, possible fatal symptoms
2. galactokinase - result in cataracts in adulthood
3. UDP-galactose-4-epimerase
asymptomatic or produce mild symptoms
results to galactosemia with toxic intermediate metabolic products
infant failure to thrive
liver disorder, cataracts, severe mental retardation
Lactosuria
may be seen during pregnancy and lactation
Fructosuria
associated with parenteral feeding
Diagnosis
Tests:
1. Copper reduction test – postive
2. Reagent strip glucose oxidase test – negative
3. Newborn screening tests
• Graff’s Textbook of Routine Urinalysis and Body Fluids by Mundt 2nd ed.• Concise Book of Medical Laboratory Technology: Methods and
Interpretations• William Clarke’s Contemporary Practice in Clinical Chemistry, 2nd ed.• Henry’s Clinical Diagnosis and Management by Laboratory Methods, 22nd
ed. by Mcpherson• Uniralysis and Other Body Fluids by Strasinger 6th ed.• Clinical Laboratory Medicine by Richard Ravel• Fundamentals of Urine and Body Fluids Analysis by Brunzel, 3rd ed.• Clinical Laboratory Science: the Basics and Routine Techniques, 6th ed. by
Turgeon• Inborn Metabolic Diseases: Diagnosis and Treatment by Saudubray 5th ed• Medical Biochemistry: Human Metabolism in Health and Disease by
Rosenthal• Clinical Chemistry: Principles, Techniques and Correlations by Bishop 7th
ed.
References