Published on February 18, 2014
Amino Acid Disorders Branched-Chain Amino Acid Disorders Purine Disorders Date submitted: February 19, 2014 Section: MD3Y2-7 Name: Pagdanganan, John Kenneth Clanor, Angelica Bonto, Mae Willrose
Amino Acid Disorders ● Amino acid disorders w/ urinary screening tests: ● ● ● ● ● ● ● ● ● Phenylketonuria Tyrosyluria Alkaptonuria Melanonuria Maple syrup urine disease Organic acidemias Indicanuria Cystinuria Cystinosis
Phenylalanine-Tyrosine Disorders ● ● Many of most frequently requested special urinalysis assoc. w/ this metabolic pathway Major inherited disorders: PKU ● Tyrosyluria ● Alkaptonuria Metabolic Defects: Melanoma ● ●
Phenylketonuria ● Most well known aminoaciduria ● 1/10k-20k births ● Can cause: Severe mental retardation if undetected ● Fair complexions due to decreased prod of tyrosine & melanin Identified in Norway by Ivan Folling (1934) ● ● ● ● ● Peculiar mousy odour of urine of mentally retarded child High levels of keto acids, inlcuding phenylpyruvate Conversion of phenylalanine to tyrosine is disrupted
● ● ● Absence of gene needed to prod. Phenylalanine hydroxylase Autosomal recessive trait: normal heterozygous carrier Newborn screening test: (+) PKU = eliminate phenylalanine in diet (major constituent in milk) = prevent excessive buildup in serum = avoid mental retardation ● Alternate pathways develop as child matures ● Aspartame: high levels of phenylalanine
● Blood Test ● ● ● ● ● Initial screening done b/f being discharged from hospital Can be detected 4hrs after birth if cutoff is lowered to 2mg/dL May need to repeat test in early visit to pediatrician Slower rise in girls- more prone to escape detection during early tests
● Microbial Inhibition Assay – Guthrie ● ● Most well-known blood test for PKU P: phenylalanine counteracts action of beta-2thienylalanine, an inhibitor of B. subtilis 1. Blood from heelstick absorbed into filter paper circles 2. Paper disks placed on CM streaked w/ B. Subtilis (+) growth around paper disk (-) no growth
● Urine Test ● ● ● ● Appears after 2-6 weeks in urine Follow up procedure in questionable diagnostic cases Screening test to ensure proper dietary control Monitoring dietary intake of pregnant women lacking phenylalanine hydroxylase
● Ferric Chloride ● ● ● ● Urine tube test testing for phenylpyrvic acid Nonspecific: reacts with other amino acids & medications False (+) produced by certain brands of disposable diapers Permanent blue-green colour 1. Place 1mL of urine in tube 2. Slowly add 5 drops of 10% ferric chloride 3. Observe colour
Tyrosyluria ● Tyrosinemia produces urinary overflow ● Inherited/Metabolic ● Since 2 reactions are directly involved in tyrosin metabolism, urine may have: ● ● Excess tyrosine Excess degraded products: ● P-hydroxyphenylpyruvic acid ● P-hydroxyphenyllactic acid
● Transitory Tyrosinemia ● ● ● ● Most frequently seen in premature infants Caused by underdevelopment of liver fxn req. to prod. enzymes needed for complete metabolism Rarely causes permanent damage Difference in urinary test w/ PKU ● Green colour fades away quickly
● Acquired liver Disease ● Resembles transitory newborn tyrosyluria ● Leucine & Tyrosine crystals seen ● Hereditary Disorders ● ● ● ● ● Absence of enzymes needed in metabolic pathway Serious & usually fatal Liver & Renal Tubular Damage Generalized aminoaciduria 3 types (all produce tyrosylemia & tysosyluria)
● Type 1: Deficient in Fumarylacetoacetate hydrolase (FAH) ● Generalized renal tubular disorder & progressive liver failure Type 2: ● ● Deficient in Tyrosine aminotransferase ● Corneal erosion; lesions of palms, fingers, & soles of feet due to crystallization of tyrosine in cells Type 3: ● ● ● ● Deficient in P-hydroxyphenylpyruvic acid dioxygenase Mental retardation if dietary restrions of phenylalanine & tyrosine not implemented
● Nitroso-naphtol Test Urinary screening test for tyrosine & its metabolites ● Nonspecific ● (+) orange-red = indicates need of further tests 1. Place 5 drops of urine in a tube 2. Add 1mL of 2.63N nitric acid 3. Add 1 drop of 21.5% sodium nitrite 4. Add 0.1mL l-nitroso-2-napthol 5.Mix 6. Wait 5 minutes 7. Observe colour MS/MS screening test ● ● ● Available for Type 1 & 2
Melanuria ● ● ● 2nd pathway of Tyrosine Responsible for prod. of melanin, thyroxine, epinephrine, protein & tyrosine sulfate Major lab concern: Melanin ● ● ● ● Confers dark hair, eye, and skin colour Deficieny: Albinism Elevated: overproliferation of melanocytes = Malignant Melanoma Tumor cells secrete 5,6-dihydroxyindole = oxidizes to melanogen, then melanin = dark urine
● Melanin reacts w/: 1. Ferric Chloride: gray/black precipitate 2. Sodium Nitroprusside (nitroferricyanide): red ● ● ● ● Glacial acetic acid: prevents intereference from creatinine & acetone Melanin: green-black Acetone: purple Creatinine: amber 3. Ehrlich Reagent
Alkaptonuria ● 1 of 6 inborn errors of metabolism ● 3rd major defect in phenylalanine-tyrosine pathway ● ● ● ● ● Absence of gene needed to prod. Homogentisic acid oxidase Homogentisic acid accumulates in blood, tissue, urine “alkali lover” - turns dark & alkali after standing in room temp Brown pigment deposited in body tissues (esp. ear); deposit in catilage (arthritis) Many develop liver & cardiac disorders
● Homogentisic acid reacts w/: 1. Ferric Chloride: transient deep blue colour 2. Clinitest: yellow precipitate 3. Alkali: darkening of urine (interference: large amounts of ascorbic acid) Silver nitrate & ammonium hydroxide: black Read: Spectrophotometer, Chromatography procedures
Branched-Chain Amino Acid Disorders ● A methyl group branches from main aliphatic carbon chain 1. accumulation of 1/more early amino acid degradation products (maple syrup urine dse) 2. organic acidemias: accumulation of organic acids further down metabolic pathway ● Ketonuria in newborn
Maple Syrup Disease ● Rare, Autosomal recessive trait, caused by IEM ● Involved: leucine, isoleucine, valine ● ● ● Absence of gene for oxidative carboxylation of keto acids (alpha-ketoisovaleric, alpha-ketoisocaproic, alpha-keto-beta-methylvaleric) = accumulation in blood & urine Failure to thrive after aprox. 1 week Maple syrup odor (11th day): due to rapid accumulation of keto acids ● REPORT! Prevent severe mental retardation & death:
● Newborn screening: MS/MS ● 2,4-dinitrophenylhydrazine (DNPH) reaction ● ● ● ● ● Most frequently performed urinary screening (+) yellow turbidity or precipitate Interferece: Large doses of ampicillin Nonspecific Treatment can be started based on odor, clinical symptoms & positive DNPH test while confirmatory prodecures are being done
● 2,4-Dinitrophenylhydrazine Test 1. Place 1mL of urine in a tube 2. Add 10 drops of 0.2% 2,4-DNPH in 2N Hcl 3. Wait 10 minutes 4. Observe for yellow/white precipitate
Organic Acidemias ● Generalized symptoms: Early severe illness ● Vomiting w/ Metabolic acidosis ● Hypoglycemia ● Ketonuria ● Increased serum ammonia Most frequent disorders: ● ● ● ● ● Isovaleric acidemia Propionic acidemia Methylmalonic acidemia
● Isovaleric Acidemia: ● ● Sweaty feet odor of urine ● Caused by accumulation of isovalerylglycine due to a deficiency of isovaleryl coenzyme A in the leucine pathway Propionic & Methylmalonic acidemia: ● ● Errors converting isoleucine, valine, threonine, methionine to succinyl coenzyme A Immediate precursor to methylmalonic acid: Propionic acid
● Newborn screening: MS/MS ● ● ● ● Isovaleric acidemia Propionic acidemia Methylmalonic acidemia Urine test: Methylmalonic aciduria ● P-nitroaniline: (+) emerald green colour
Purine Disorders ● Lesch-Nyhan Disease ● ● ● ● ● ● Sex linked recessive Massive excretion of uric acid crystals Absence of Hypoxanthine guanine phosphoribosyltransferase Severe motor defects, mental retardation, tendency towards self-destruction, gout, renal calculi First 6-8 months: normal development First symptom: (uric acid) orange sand in diapers
Source: Urinalysis and Body Fluids, 5th edition by Susan King Strasinger & Marjorie Schaub Di Lorenzo
The disorders of purine and pyrimidine metabolism are ... A number of disorders of purine metabolism lead ... In purine metabolism, inosinic acid ...
Disorders of amino acid metabolism. ... Mitochondrial disorders Lysosomal storage disorders Peroxisomal disorders Purine and pyrimidine disorders ...
Overview of Purine and Pyrimidine Metabolism Disorders. ... Chain Amino Acid Metabolism Disorders; ... complete catabolism of purines is uric acid; ...
Inborn errors of pyrimidine metabolism: clinical update ... is currently restricted to only two disorders: ... uric acid in purine metabolism, ...
Disorders of purine and pyrimidine metabolism. ... A number of disorders of purine metabolism lead to immunodeficiency; ... Purines/metabolism*
Disorders of metabolism purine and pyrimidine; ... • disorders of uric acid metabolism • disorders of purines ... materials such as amino acids and ...
Disorders of Amino Acid Metabolism. ... of amino acids or in the body’s ability to get amino acids into cells. Because these disorders cause symptoms ...
Genetic disorders of purine and pyrimidine (PP) metabolism are ... In purine metabolism, uric acid is ... i.e. investigations for amino acid disorders, ...
Overview of purine metabolism ... disorders * handling of uric acid by the kidneys (URAT1 and UAT1) * overproduction of uric acid can lead to hyperuricemic