Urine Screening for Metabolic Disorders PDF

6/25/2024 Urine Screening for Metabolic Disorders Chapter 9 Preamble PowerPoints are a general overview and are provided to help students take notes over the video lecture ONLY. PowerPoints DO NOT cover the details needed for the Unit exam Each student is responsible...

6/25/2024 Urine Screening for Metabolic Disorders Chapter 9 Preamble PowerPoints are a general overview and are provided to help students take notes over the video lecture ONLY. PowerPoints DO NOT cover the details needed for the Unit exam Each student is responsible for READING the TEXTBOOK for details to answer the UNIT OBJECTIVES Unit Objectives are your study guide (not this PowerPoint) Test questions cover the details of UNIT OBJECTIVES found only in your Textbook! 1  6/25/2024 Overflow Versus Renal Disorders Overflow Disruption of a normal metabolic pathway Increased plasma concentrations of the nonmetabolized substances Overrides reabsorption ability of renal tubules Inherited lack of specific enzyme for protein, fat, or carbohydrate metabolism—inborn error of metabolism Renal Malfunctions in the tubular reabsorption mechanism Disorders Classified by Defect Table 9-3 Major Disorders of Protein and Carbohydrate Metabolism Associated With Abnormal Urinary Constituents, Classified by Functional Defect Overflow Inherited Metabolic Renal Phenylketonuria Infantile tyrosinemia Hartnup disease Tyrosinemia Melanuria Cystinuria Alkaptonuria Indicanuria Maple syrup urine disease 5-Hydroxyindoleacetic acid Organic acidemias Porphyria Cystinosis Porphyria Mucopolysaccharidoses Galactosemia Lesch-Nyhan disease 2  6/25/2024 Newborn Screening Tests Current state-mandated screening for as many as 31 inborn errors of metabolism (IEM) Performed before infant leaves Heel stick blood tests are hospital used for testing But >24 h Metabolites appear first in the blood Analyze by tandem mass spectrophotometry, MS/MS Amino Acid Disorders Disorders with urinary screening Phenylketonuria Tryosyluria Melanuria Alkaptonuria Maple syrup urine disease Organic acidemias Indicanuria Cystinuria Cystinosis 3  6/25/2024 Phenylalanine-Tyrosine Disorders Major inherited disorders PKU Tyrosyluria Alkaptonuria Metabolic defects cause overproduction of melanin Phenylketonuria Phenylketonuria 1 in 10,000 to 20,000 births Results in severe intellectual disability First identified by Ivan Følling in 1934 Seizures, hyperactivity, development delay and psychiatric disturbances may be present Autosomal recessive; heterozygotes normal Eliminate phenylalanine from diet (milk) Damage to child’s mental capacity Avoid ↑ phenylalanine foods (aspartame) 4  6/25/2024 Phenylketonuria (continued) Eliminate phenylalanine from diet (milk) Damage to child’s mental capacity Avoid ↑ phenylalanine foods (aspartame) Phenylalanine can be detected as early as 4 hours after birth Urine and 5% ferric chloride produces a permanent Urine test green-blue color Tyrosyluria Metabolic defects Premature transient tyrosinemia Underdevelopment of liver function Acquired severe liver disease 3 Types of Hereditary defects Type 1: enzyme deficiency is fumarylacetoacetate acid hydrolase; renal tubular disease and liver failure in infants Type 2: enzyme deficiency is tyrosine aminotransferase; corneal erosion and lesions on hands and feet Type 3: enzyme deficiency is p-hydroxyphenylpyruvate acid dioxygenase; intellectual disability, seizures and ataxia can result if there are no dietary restrictions (milk) 5  6/25/2024 Tyrosyluria (continued) Screening tests Screening tests using MS/MS are available for tyrosinemia types 1, 2, and 3 Nitro-Napthol 5 drops of urine in tube 1 ml 0f 2.63 N nitric acid 1 drop of 21.5% NaNO3 NITRO- Add 0.1 mL 1-nitroso-2-napthol NAPTHOL Mix Wait 5 minutes Positive for tyrosine metabolite = Orange –red color; In Ferris chloride test = fading green Melanuria Second pathway for tyrosine Melanin, thyroxine, epinephrine, protein, and tyrosine sulfate Melanin Pigment for dark hair, skin Deficiency causes albinism Increased production = malignant melanoma 5,6-dihydroxyindole Dark urine from oxidation of melanogen to melanin 6  6/25/2024 Alkaptonuria Third major defect in the phenylalanine-tyrosine pathway Enzyme deficiency is caused by a failure to inherit the gene to produce the enzyme homogentisic acid oxidase Black alkaline urine, possible black-stained diapers Manifests later in life with brown pigment deposits in tissues High percentage of people develop liver and cardiac issues Urine: blue with ferric chloride, yellow precipitate with Clinitest, black with silver nitrate and ammonium hydroxide; quantitative tests available 4 ml of 3% silver nitrate in a tube Silver 0.5 ml of urine mix Nitrate add 10% of NH4 OH by drops watch for black to develop Branched Chain Amino Acid Disorders Amino acids with a methyl group that Two groups Ketonuria in a newborn branches from the main aliphatic carbon chain Maple syrup urine disease (MSUD); early degradation products accumulate Organic acidemias; accumulation of organic acids further down in pathway 7  6/25/2024 Maple Syrup Urine Disease (MSUD) Inborn error of metabolism, autosomal recessive Amino acids involved are leucine, isoleucine, and valine 1-week failure to thrive is noticed Urine: strong odor of maple syrup Dietary regulation by day 11 shows good outcomes Positive urine ketones Screening test 2,4-dinitrophenylhydrazine produces yellow precipitate turbidity Place 1 mL of urine in a tube. 2, 4- Add 10 drops of 0.2% 2,4-DNPH in 2N HCl. Dinitrophenylhydrazine (DNPH) Test Wait 10 minutes. Observe for yellow or white precipitate. Organic Acidemias Early: severe vomiting, metabolic acidosis, hypoglycemia, ketonuria, increased serum ammonia Isovaleric, propionic, methylmalonic acidemias Isovaleric: “sweaty feet odor” from patient Deficiency of isovaleryl coenzyme A Propionic and methylmalonic: no conversion of valine, threonine, methylmalonate to succinyl coenzyme A Isovaleric, propionic, and methylmalonic acidemias can be detected by newborn screening programs using MS/MS 8  6/25/2024 Tryptophan Disorders Increased urinary excretion of the metabolites indican and 5- hydroxyindoleacetic acid (5-HIAA) Indicanuria Tryptophan enters intestine, is reabsorbed or is converted to indole by bacteria, and leaves in the feces Intestinal disorders and Hartnup disease cause increased tryptophan conversion to indole Increased indole reabsorbed, excreted by kidney on its way to the liver Exposure of urine to air = indigo blue Hartnup disease: blue diaper syndrome Inherited disorder affects intestinal reabsorption of indole and renal tubular reabsorption = Fanconi syndrome Requires dietary supplements: niacin 9  6/25/2024 5-Hydroxyindoleacetic Acid (5-HIAA) Tryptophan produces serotonin Serotonin from tryptophan is produced by the intestinal argentaffin cells and is carried through the body by platelets (primarily) Excess excreted in the urine as 5-HIAA Argentaffin (enterochromaffin) cell tumors = ↑ ↑ 5-HIAA in urine from excess serotonin produced Nitrous acid and 1-nitroso-2-naphthol produce purple to black color Urine test Normal 2 to 8 mg/day, >25 mg/day in disease Can perform test on random specimens Cystine Disorders Two distinct disorders; both have noticeable odor of sulfur Cystinuria Inherited disorder affecting renal reabsorption Two modes of inheritance: (1) only cystine and lysine are not reabsorbed; (2) cystine, lysine, arginine, and ornithine are not reabsorbed Increased calculi formation early in life for both modes Approximately 65% of the people in whom all four amino acids are affected can be expected to produce calculi early in life 10  6/25/2024 Cystine Disorders (continued) Cystine is the least soluble accounting for cystine crystals Cystine is also the only amino acid found during the analysis of calculi from these patients Urine screening test: cyanide-nitroprusside Na cyanide reduces cystine, and nitroprusside produces a red-purple color if excess cystine is present False-positives: ketonuria, homocystinuria Place 3 mL of urine in a tube. Add 2 mL sodium cyanide. Cyanide- Wait 10 minutes. Nitroprusside Test Add five drops 5% sodium nitroprusside. Observe for red-purple color. Cystinosis Two categories Defect in lysosomal Ranging from a severe Nephropathic membranes prevents fatal disorder developed Infantile release of cystine into Genuine IEM in infancy to a benign Later life cytoplasm for form appearing in Non-nephropathic metabolism = crystalline adulthood cystine deposits in body 11  6/25/2024 Cystinosis (continued_1) Deposits: cornea, bone marrow, lymph nodes, organs Renal tubules are affected by deposits causing Fanconi syndrome, which is not inherited Infantile: rapid progression to renal failure Late-onset: gradual progression to renal failure Non-nephropathic: benign, some ocular problems Laboratory: polyuria, aminoaciduria, reducing substances, lack of urinary concentration Homocystinuria Defect in metabolism of methionine, producing increased homocysteine in body Failure to thrive, cataracts, intellectual disability, thromboemboli, stroke, death Requires changes in diet Additional screening with silver nitrate instead of sodium cyanide Fresh urine should be used Place 1 mL of urine in a tube. Add two drops concentrated NH4OH. Silver Add 0.5 mL 5% silver nitrate. Nitroprusside Test Wait 10 minutes. Add five drops sodium nitroprusside. Observe for red-purple color. 12  6/25/2024 Porphyrin Disorders Intermediate compounds in the production of heme Primary porphyrins: uroporphyrin, coproporphyrin, protoporphyrin Precursors: α-aminolevulinic acid (ALA) and porphobilinogen Detection of pathway disruptions in urine, blood, bile, and feces Urine: ALA, porphobilinogen, urobilinogen Feces/bile: coproporphyrin, protoporphyrin Blood: free erythrocyte protoporphyrin (FEP) for lead poisoning Porphyrin Disorders (continued_1) Collectively termed porphyrias Acquired (more common): lead poisoning, alcoholism, iron deficiency, chronic liver and renal disease Inherited: rare; gene in metabolic pathway is missing Classified by clinical symptoms as neurologic/psychiatric, cutaneous/photosensitivity, or both Urine: port wine color after air exposure, also seen on diapers Convert ALA to porphobilinogen by adding acetyl acetone Ehrlich reaction: only for ALA and porphobilinogen Watson-Schwartz test-differentiation between urobilinogen and porphobilinogen Fluorescence under ultraviolet light 550- to 600-nm Violet, pink, red, based on concentration range is used for other porphyrins; extract into glacial acetic acid and ethyl acetate; does not distinguish 13  6/25/2024 Porphyrin Disorders: Watson-Schwartz Differentiation Test 2 mL urine Tube 1 2 mL chloroform 4 mL sodium acetate 2 mL urine 2 mL butanol Tube 2 4 mL sodium acetate Observe the color of the layers Porphyrin Disorders: Hoesch Test Two drops of urine are added to approximately 2 mL of Hoesch reagent Immediately observe the top of the solution for the appearance of a red color that Hoesch Test indicates the presence of porphobilinogen Shake the tube Test is most useful when patients exhibit symptoms of an acute attack 14  6/25/2024 Mucopolysaccharide Disorders Inherited disorders preventing the metabolism of glycoaminoglycans in the connective tissue Incompletely metabolized polysaccharides accumulate in connective tissue Substances found in urine are dermatan sulfate, keratan sulfate, and heparin sulfate Mucopolysaccharidoses 1. Hurler syndrome: abnormal skeletal structure, severe, and corneal damage 2. Hunter syndrome: abnormal skeletal structure, severe intellectual disability, inherited as a sex-linked recessive trait, rare in females 3. Sanfilippo syndrome: intellectual disability 4. Hurler and Hunter syndrome is fatal without treatment Bone marrow transplantation and gene therapy Mucopolysaccharide Disorders (continued_1) Urinary screening tests may be requested on newborns/infants who exhibit symptoms of intellectual disability of failure to thrive Acid-albumin and cetyltrimethylammonium bromide (CTAB) turbidity tests Thick, white precipitate Metachromatic staining spot tests Place 5 mL of urine in a tube. Cetytrimethylammonium Add 1 mL 5% CTAB in citrate buffer. Bromide (CTAB) Test Read turbidity in 5 minutes. 15  6/25/2024 Purine Disorders Lesch-Nyhan disease Inherited sex-linked recessive Massive excretion of uric acid crystals Motor defects, intellectual disability, self-destruction, gout, renal calculi Normal development 6 to 8 months Orange sand in diaper Be alert for increased uric acid crystals in pediatric patients Carbohydrate Disorders Termed melituria; frequently due to inherited disorder No problems except for galactosuria Failure to thrive combined with liver disorders, cataracts, severe intellectual disability Remove lactose from the diet Three enzymes: galactose-1-phosphate uridyl transferase, galactokinase, UDP-galactose-4-epimerase 16  6/25/2024 Carbohydrate Disorders (continued_1) GALT deficiency causes severe, possible fatal symptoms Included in newborn testing of RBCs Clinitest positive Other causes of melituria Lactosuria Pregnancy and lactation Fructosuria Parenteral feeding Pentosuria Ingestion of large amounts of fruit Postamble READ the TEXTBOOK for the details to answer the UNIT OBJECTIVES. USE THE UNIT OBJECTIVES AS A STUDY GUIDE All test questions come from detailed material found in the TEXTBOOK (Not this PowerPoint) and relate back to the Unit Objectives 17