URINE SCREENING FOR METABOLIC DISORDERS

• Amino Acid Disorders

  Phenylalanine-Tyrosine Disorders

  Branched-Chain Amino Acid Disorders

  Tryptophan Disorders

  Cystine Disorders
• Phenylalanine-Tyrosine Disorders

  Phenylketonuria

  Tyrosyluria

  Melanuria

  Alkaptonuria
• Branched-Chain Amino Acid Disorders

  Maple Syrup Urine Disease

  Organic Acidemias
• Tryptophan Disorders

  Indicanuria

  5-Hydroxyindoleacetic Acid
• Cystine Disorders

  Cystinuria

  Cystinosis

  Homocystinuria
• URINE SCREENING FOR METABOLIC DISORDERS

  Amino Acid Disorders

  Porphyrin Disorders

  Mucopolysaccharide Disorders

  Purine Disorders

  Carbohydrate Disorders
• Phenylketonuria

  identified by Ivan Folling in 1934 in Norway

  seen in 1 of every 10,000 to 20,000 births

  autosomal recessive trait

  failure to inherit gene that codes for phenylalanine hydroxylase
• Phenylketonuria

  Guthrie’s Microbial Inhibition Assay

  Ferric chloride tube test
• presence of tyrosine or its degradation products in urine

  can be inherited or metabolic in nature

  Tyrosyluria
• Alkaptonuria


  described by Garrod in 1902

  failure to inherit gene that code for homogentisic acid oxidase

  accumulation of homogentisic acid in blood, tissues and urine

  may develop liver and cardiac disorders
• Alkaptonuria

  Early childhood – brown/black-stained

  cloth diapers and reddish-stained

  disposable diapers

  Adults – brown pigment deposition in

  body tissues (noticeable in ears)
• affects the alternate pathway for degradation of tyrosine

  Melanuria
• indicates over proliferation of melanocytes producing malignant melanoma

  Melanuria
• Melanuria Tests:

  Ferric chloride test

  Sodium nitroprusside/nitroferricyanide

  Ehrlich’s test
• BRANCHED-CHAIN AMINO ACID

  DISORDERS

  Maple Syrup Urine Disorder (MSUD)
• Maple Syrup Urine Disorder (MSUD)

  autosomal recessive trait

  failure to inherit gene that code for enzyme necessary for

  oxidative decarboxylation of involve amino acids

  associated with infant “failure to thrive” after 1 week

  indicated by strong maple syrup odor of urine
• TRYPTOPHAN DISORDERS

  Indicanuria
• Malabsorption syndromes

  Hartnup disease

  Indicanuria
• Hartnup disease

  Ferric chloride tube test

  5-hydroxyindoleacetic acid (5-HIAA)
• caused by increased serotonin level

  brought by carcinoid tumors of argentaffin cells

  5-hydroxyindoleacetic acid (5-HIAA)
• Ferric chloride tube test

  (+):

  deep blue or violet
• 5-hydroxyindoleacetic acid (5-HIAA) Test:

  Nitroso-naphthol test
• Nitroso-naphthol test

  (+):

  purple to black color
• CYSTINE DISORDERS

  Cystinuria

  Cystinosis

  Homocystinuria
• due to inability of tubules to reabsorb cystine

  Cystinuria
• Cystinuria

  Tests:

  Microscopic examination of urine

  (+): presence of cystine crystals

  Cyanide-nitroprusside test

  (+): red purple color
• true inborn error of metabolism form of cystine disorder

  Cystinosis
• Cystinosis 2 categories:

  Nephropathic

  Non-Nephropathic
• can be infantile or late-onset

  Nephropathic
• due to defect in lysosomal membranes preventing release of cystine in many areas of the body

  Nephropathic
• relatively benign but may cause some ocular disorders

  Non-Nephropathic
• defect in metabolism of methionine

  Homocystinuria
• can lead to infant failure to thrieve, cataract, mental retardation, thromboembolic problems,

  and death

  Homocystinuria
• Homocystinuria Tests:

  Modified guthrie’s microbial inhibition assay

  Silver nitroprusside test

  (+): red purple color
• can be inherited or acquired

  PORPHYRIN DISORDERS
• PORPHYRIN DISORDERS

  Lead poisoning

  Excessive alcohol exposure

  Iron deficiency

  Chronic liver disease

  Renal disease
• PORPHYRIN DISORDERS Tests:

  Ehrlich reaction

  Fluorescence test
• for ALA and porphobilinogen for PORPHYRIN DISORDERS

  Ehrlich reaction
• Most common mucopolysaccharidoses:

  Hurler syndrome

  Hunter syndrome

  Sanfilippo syndrome
• accumulation of mucopolysaccharides in cornea

  Hurler syndrome