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AUBF > 7.1 METABOLIC DISORDERS - INTRO, AMINO ACID DISORDERS > Flashcards

7.1 METABOLIC DISORDERS - INTRO, AMINO ACID DISORDERS Flashcards

1
Q

What are most abnormal results in routine urinalysis related to?

A

Metabolic diseases

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2
Q

What can urine as an end product of body metabolism contain that is not tested in routine urinalysis?

A

Additional abnormal substances.

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3
Q

How can additional abnormal substances in urine be detected?

A

Additional screening tests

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4
Q

What can positive screening tests be followed by?

A

Sophisticated procedures in other lab sections.

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5
Q

What observations can indicate the need for additional urine tests?

A

Abnormal specimen color and odor or clinical symptoms and family histories.

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6
Q

What are the two categories of disorders that cause abnormal metabolic substances in urine?

A

Overflow disorders and renal disorders

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7
Q

Disruption of normal metabolic pathways leading to increased plasma concentrations of nonmetabolized substances.

A

overflow disorders

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8
Q

Malfunctions in the tubular reabsorption mechanism.

A

renal disorders

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9
Q

What types of metabolic disturbances most frequently produce urinary overflow?

A

Disturbances in the metabolism of protein, fat, and carbohydrates

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10
Q

What can disrupt enzyme function in metabolic pathways?

A

Inborn errors of metabolism (IEMs) or organ malfunction.

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11
Q

Failure to inherit the gene to produce a particular enzyme

A

inborn error of metabolism (IEM)

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12
Q

What was the traditional purpose of many urine tests discussed in this chapter?

A

Detecting and monitoring newborns for IEMs.

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13
Q

How many core conditions and secondary target conditions do many states mandate newborn screening for?

A

31 core conditions and 25 secondary target conditions.

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14
Q

Why is early detection of defects causing IEMs important?

A

To prevent the buildup of unmetabolized toxic food ingredients

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15
Q

In IEM detection, where are elevated levels of substances detected more rapidly?

A

In blood

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16
Q

What method is primarily used for testing infant blood for IEMs?

A

Tandem mass spectrophotometry (MS/MS).

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17
Q

What does MS/MS screening detect?

A

Specific substances associated with particular IEMs.

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18
Q

What is being developed rapidly for detecting IEMs?

A

Specific gene testing methods.

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19
Q

What are the subgroups of disorders under amino acid disorders?

A

Phenylalanine-tyrosine disorders,
branched-chain amino acid disorders, tryptophan disorders, and
cystine disorders.

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20
Q

What are the disorders under phenylalanine-tyrosine disorders?

A

Phenylketonuria (PKU),
tyrosyluria,
melanuria, and
alkaptonuria.

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21
Q

What metabolic defect results in overproduction of melanin?

A

Phenylalanine-tyrosine disorders

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22
Q

What are the disorders under branched-chain amino acid disorders?

A

Maple syrup urine disease (MSUD) and

organic acidemias (isovaleric, propionic, and methylmalonic acidemia).

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23
Q

What are the disorders under tryptophan disorders?

A

Indicanuria and
5-hydroxyindoleacetic acid (5-HIAA) overproduction.

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24
Q

What are the disorders under cystine disorders?

A

Cystinuria and cystinosis.

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25
Q

What disorder is characterized by a failure to inherit the enzyme phenylalanine hydroxylase, resulting in intellectual disability if untreated?

A

Phenylketonuria (PKU).

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26
Q

Which disease produces a “mousy odor” in urine and sweat due to phenylpyruvic acid accumulation?

A

Phenylketonuria (PKU)

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27
Q

What autosomal recessive disorder leads to reduced melanin production, causing lighter skin and hair in affected individuals?

A

Phenylketonuria (PKU).

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28
Q

What symptom is commonly observed in infants with PKU?

A

Mousy odor in urine and sweat.

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29
Q

How is PKU screened in newborns?

A

By testing blood phenylalanine levels between 24–48 hours after birth

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30
Q

Which disease results in tyrosine accumulation due to enzyme deficiencies or immature liver function in newborns?

A

Tyrosyluria

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31
Q

What type of tyrosinemia involves a deficiency in the enzyme fumarylacetoacetate hydrolase and causes renal and liver failure in infants?

A

Tyrosinemia Type 1

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32
Q

What disease is caused by a deficiency in tyrosine aminotransferase, leading to corneal erosions and skin lesions?

A

Tyrosinemia Type 2.

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33
Q

Which type of tyrosinemia is characterized by intellectual disability and ataxia due to a lack of p-hydroxyphenylpyruvic acid dioxygenase?

A

Tyrosinemia Type 3.

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34
Q

What causes type 1 tyrosinemia?

A

Deficiency of fumarylacetoacetate hydrolase (FAH).

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35
Q

What are the symptoms of type 2 tyrosinemia?

A

Corneal erosions and skin lesions on palms and soles.

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36
Q

Which metabolite is elevated in type 3 tyrosinemia?

A

4-hydroxyphenylpyruvic acid.

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37
Q

What indicates increased melanin production in urine?

A

Dark urine after exposure to air.

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38
Q

Which condition is associated with malignant melanocytes?

A

Melanuria

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39
Q

Which disorder results from a deficiency in homogentisic acid oxidase, leading to black-stained urine and ochronosis?

A

Alkaptonuria

40
Q

What autosomal recessive disorder involves brown pigment deposits in tissues and can lead to arthritis and cardiac complications?

A

Alkaptonuria

41
Q

What enzyme deficiency causes alkaptonuria?

A

Homogentisic acid oxidase.

42
Q

What classic symptom is seen in alkaptonuria?

A

Dark urine upon standing at room temperature.

43
Q

Which amino acids accumulate in MSUD?

A

Leucine, isoleucine, and valine.

44
Q

What is the characteristic urine odor in MSUD?

A

Maple syrup-like smell.

45
Q

Which disease produces a sweet, “maple syrup” odor in urine due to branched-chain keto acid accumulation?

A

Maple Syrup Urine Disease (MSUD).

46
Q

Which branched-chain amino acid disorder causes a “sweaty feet” odor in urine due to isovalerylglycine accumulation?

A

Isovaleric Acidemia.

47
Q

What common metabolic defect is shared by propionic and methylmalonic acidemia?

A

Errors in converting amino acids to succinyl CoA.

48
Q

Which organic acidemia disorders result from defects in the conversion of isoleucine, valine, threonine, and methionine to succinyl CoA?

A

Propionic acidemia and methylmalonic acidemia

49
Q

What disorder causes blue-stained diapers (blue diaper syndrome) due to excessive indican in urine?

A

Indicanuria (associated with Hartnup disease).

50
Q

What disorder is associated with carcinoid tumors and increased serotonin metabolism, resulting in elevated urinary 5-HIAA?

A

5-Hydroxyindoleacetic Acid (5-HIAA) elevation.

51
Q

Intestinal disorders leading to increased tryptophan metabolism to indole

A

indicanuria

52
Q

What tumor is associated with elevated 5-HIAA levels?

A

Argentaffin cell (carcinoid) tumors.

53
Q

What dietary items interfere with 5-HIAA testing?

A

Bananas, avocados, tomatoes, and walnuts.

54
Q

What is the main defect in cystinuria?

A

Failure to reabsorb cystine in renal tubules.

55
Q

What is the primary manifestation of cystinuria?

A

Formation of cystine renal calculi

56
Q

What disorder involves a renal tubular defect leading to poor reabsorption of cystine and potential formation of cystine kidney stones?

A

Cystinuria

57
Q

Which inherited disorder results in cystine accumulation in lysosomes, causing organ damage?

A

Cystinosis

58
Q

What is cystinosis characterized by?

A

Intracellular accumulation of cystine in lysosomes.

59
Q

What systemic effects are associated with cystinosis?

A

Renal failure and growth retardation

60
Q

What dietary intervention is critical for managing PKU?

A

Eliminating phenylalanine from the diet.

61
Q

Which screening test detects phenylpyruvic acid in PKU patients?

A

Ferric chloride test.

62
Q

What test is used to detect tyrosyluria by reacting with nitroso-naphthol?

A

Qualitative urine screening test.

63
Q

What test produces a deep blue color when detecting homogentisic acid in urine?

A

Ferric chloride test

64
Q

What is the specific genetic mutation responsible for most cases of PKU?

A

Mutations in the PAH (phenylalanine hydroxylase) gene

65
Q

What is the key cofactor required by phenylalanine hydroxylase that can also be deficient in some cases of PKU?

A

Tetrahydrobiopterin (BH4).

66
Q

What are the common clinical features of untreated PKU in infants?

A

Intellectual disability, microcephaly, seizures, and behavioral problems.

67
Q

What newborn screening method is commonly used to detect PKU?

A

Guthrie bacterial inhibition assay

68
Q

What amino acid becomes essential in patients with PKU?

A

Tyrosine

69
Q

What metabolic byproduct is elevated in the urine of patients with tyrosyluria?

A

Tyrosine and its derivatives, such as p-hydroxyphenylpyruvic acid.

70
Q

What is a distinguishing feature of Type 1 tyrosinemia compared to other types?

A

Presence of succinylacetone in the urine.

71
Q

What medication is used to treat Type 1 tyrosinemia by inhibiting the production of toxic metabolites?

A

Nitisinone (NTBC)

72
Q

What enzyme deficiency causes Type 2 tyrosinemia?

A

Tyrosine aminotransferase

73
Q

What characteristic clinical symptom is associated with Type 2 tyrosinemia?

A

Painful keratotic plaques on the palms and soles

74
Q

What color does homogentisic acid turn when exposed to air?

A

Black

75
Q

What long-term complication of alkaptonuria affects the heart?

A

Calcification of heart valves

76
Q

Which connective tissue condition is associated with ochronosis in alkaptonuria?

A

Arthritis, especially in large weight-bearing joints.

77
Q

What laboratory test can confirm the presence of homogentisic acid in urine?

A

Benedict’s test or chromatography techniques

78
Q

Which enzyme complex is deficient in MSUD?

A

Branched-chain alpha-keto acid dehydrogenase (BCKD) complex

79
Q

What are the three amino acids that accumulate in MSUD?

A

Leucine, isoleucine, and valine

80
Q

What is the common clinical presentation of MSUD in neonates?

A

Poor feeding, vomiting, lethargy, and sweet-smelling urine.

81
Q

What dietary treatment is essential for MSUD management?

A

A low-protein diet with restricted intake of branched-chain amino acids

82
Q

Which amino acid is the primary contributor to neurotoxicity in MSUD?

A

Leucine

83
Q

What enzyme deficiency causes isovaleric acidemia?

A

Isovaleryl-CoA dehydrogenase.

84
Q

What triggers acute metabolic crises in isovaleric acidemia?

A

High protein intake or infection.

85
Q

What treatment can help neutralize accumulated organic acids in isovaleric acidemia?

A

Glycine or carnitine supplementation

86
Q

What dietary deficiency exacerbates symptoms of Hartnup disease?

A

Niacin (vitamin B3).

87
Q

What is the source of the blue discoloration in “blue diaper syndrome”?

A

Indican oxidized to indigo blue.

88
Q

Which amino acid’s absorption is defective in Hartnup disease?

A

Tryptophan

89
Q

What neurological symptoms are associated with Hartnup disease?

A

Ataxia, photodermatitis, and mental changes

90
Q

What amino acids are poorly reabsorbed in cystinuria?

A

Cystine, lysine, arginine, and ornithine.

91
Q

What is the most common clinical manifestation of cystinuria?

A

Recurrent cystine kidney stones

92
Q

What test is used to diagnose cystinuria by detecting cystine in urine?

A

Cyanide-nitroprusside test.

93
Q

What medication is used to increase cystine solubility and reduce stone formation in cystinuria?

A

Penicillamine

94
Q

What organ is most affected in nephropathic cystinosis?

A

Kidneys, leading to Fanconi syndrome

95
Q

What intracellular structure accumulates cystine in cystinosis?

A

Lysosomes

96
Q

What is the primary treatment for cystinosis to prevent cystine accumulation?

A

Cysteamine therapy

97
Q

What complication of cystinosis often appears in adulthood?

A

Retinal blindness.

AUBF (22 decks)

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