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MFM Week 2 > 3 Biochemical Genetics > Flashcards

3 Biochemical Genetics Flashcards

1
Q

What is biochemical genetics?

A

These are sometimes referred to as “metabolic diseases” and there is usually treatment. A gene is mutated and the biochemical function usually cannot occur and this may cause disease. It encompasses disorders of amino and organic acids, fatty acid oxidation, nucleic acids, and vitamins and minerals.

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2
Q

What is the pattern of inheritance if the protein involved in the metabolic disease is an enzyme?

A

Typically inherited in an autosomal recessive manner

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3
Q

What is the pattern of inheritance if the protein involved in the metabolic disease is a structural protein?

A

Often inherited in an autosmoal dominant manner

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4
Q

What type of disorder is phenylketonuria?

A

Amino acid disorder

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5
Q

How do you diagnose PKU?

A

Elevation of diagnostic amino acids (F) on amino acid quantification (plasma)

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6
Q

What type of disorder is methylmalonic aciduria?

A

Organic acid disorder

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7
Q

How do you diagnose methylmalonic aciduria?

A

Elevation of diagnostic organic acid in urine

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8
Q

What type of disorder is ornithine transcarbamylase (OTC)?

A

Urea cycle defects

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9
Q

How do you diagnose ornithine transcarbamylase (OTC)?

A

Elevation of ammonia and diagnostic amino acid

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10
Q

What type of disorder is hereditary fructose intolerance (HF1)?

A

Carbohydrate

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11
Q

How do you diagnose hereditary fructose intolerance (HF1)?

A

Clinical suspicion

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12
Q

What type of disorder is Lesch-Nyhan syndrome?

A

Purines/Pyrimidines

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13
Q

How do you diagnose Lesch-Nyhan syndrome?

A

Hyperuricemia (excess uric acid in the blood)

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14
Q

What kind of disorder is Medium acyl-CoA dehydrogenase (MCAD)?

A

Lipids

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15
Q

How do you diagnose Medium acyl-CoA dehydrogenase (MCAD)?

A

Diagnostic intermediates on urine organic acid quantitation

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16
Q

What type of disorder is Biotinidase?

A

Vitamins

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17
Q

How do you diagnose Biotinidase

A

Clinical suspicion and relevant laboratory studies

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18
Q

What type of disorder is Hunter syndrome?

A

Lysosmal storage disorder

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19
Q

How do you diagnose Hunder syndrome?

A

Clincial and radiologic signs and symptoms, relevant laboratory studies for disorder

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20
Q

What type of disorder is Zellweger syndrome?

A

Peroxisomal disorders

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21
Q

How do you diagnose Zellweger syndrome?

A

Elevated very long chain fatty acids and phytanic acid

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22
Q

What type of disorder is MELAS?

A

Mitochondrial disorder

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23
Q

How do you diagnose MELAS?

A

Elevated lactic acid

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24
Q

When does PKU present?

A

Normal neonate, developmental delay beginning around 3-4 months

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25
Q

Why is phenylketonuria harmful?

A

In PKU, phenylalanine (essential amino acid) cannot be metabolized. This happens because there is an enzyme defecienty of phenylalanine hydroxylase (PAH) and the conversion of F to tyrosine (Y) is blocked. The buildup of F is neurotoxic.

26
Q

How do you treat PKU?

A

Diet low in phenylalanine (protein), rare (Kuvan, enzyme replacement)

27
Q

When does methylmalonic aciduria present?

A

Severe acidosis disorder presenting in first week of life

28
Q

Why is methylmalonic aciduria harmful?

A

Acidosis occurs because the lack of enzyme activity of methylmalonyl-CoA mutase. This enzyme is responsivle for converting methylmalonyl-CoA to succinyl-CoA (Krebs cycle).

29
Q

What are the clinical labartory findings for methylmalonic aciduria?

A

Methylmalonic acid is elevated in urine organic acid quantitation

30
Q

When is methylmalonyl-CoA produced?

A

Methylmalonyl-CoA is produced in the catabolism of certain amino acids, cholesterol and odd-chain fatty acids

31
Q

How is methylmalonic aciduria treated?

A

Treated by diet low in protein

32
Q

When does a urea cylce defect present?

A

Neonate - enzymatic defects early in the cycle results in severe, dangerous hyperammonemia in the neonate

33
Q

What are urea cycle defects?

A

Defect in the pathway converting toxic ammonia to non-toxic urea

34
Q

What are the clinical labartory findings for ornithine transcarbamylase deficiency (OTC)?

A

low citrulline and high oronic acid

35
Q

How is OTC treated?

A

treated with low protein diet and ammonia scavenger medications

36
Q

What is the result if OTC is not treated?

A

Can result in severe neurologic damage if not treated rapidly

37
Q

What is the pattern of inheritance for OTC?

A

X-linked recessive disorder (mostly boys are affected)

38
Q

Why is hereditary fructose intolerance harmful?

A

Lack of Aldose B enzyme (fructoaldolase) which metabolized fructose to glucose. Ingestion of fructose leads to vomiting, hypoglycemia acutely, chronic ingestion causes hepatomegaly and renal dysfunction

39
Q

What are the clinical labartory findings for HFI?

A

Clinical suspicion and molecular analysis of aldolase B

40
Q

How do you treat HFI?

A

Treatment includes restricking fruit, vegetables, corn syrup, table sugar to prevent symptoms

41
Q

What defect occurs in Lesch-Nyhan disease?

A

Disorder of purine reclamation, due to defect in hypoxanthine-guanine phosphoribosyltransferase activity (HGPRT)

42
Q

What behaviors are present with Lesch-Nyhan disease?

A

Neurologic dysfunction and self-mutilation behavior

43
Q

What are the clinical labartory findings for Lesch-Nyhan disease?

A

clinical suspicion, elevated uric acid and molecular analysis of HGPRT

44
Q

How is Lesch-Nyhan disease treated?

A

Treated with low protein diet, allopurinol, medications for treatment of neurologic signs and symptoms

45
Q

What is the pattern of inheritance for Lesch-Nyhan disease?

A

X-linked recessive disorder (mostly boys are affected)

46
Q

When does meduium chain acyl-CoA dehydrogenase deficiency (MCAD) present?

A

Often presents as a child with lethargy an dvomiting following fasting, classically presents with hypoketotic and hypoglycemia, may be entirely asymptomatic

47
Q

What are the clinical labartory findings for MCAD?

A

Elevations of fatty acid oxidation intermediates on urine organic acid quantitation and acylcarnitine analysis

48
Q

How is MCAD treated?

A

Treated by avoidance of fasting and rapid treatment of hypoglycemia

49
Q

When does biotinidase present?

A

Signs and symptoms include alopecia, dermatitis, deafness, seizures, neurologic deterioration starting about 4-6 months of age

50
Q

Why is biotinidase harmful?

A

It is a disorder in the reclammation or recycling of the vitamin biotin. Biotin is improtant in carboxylation reactions, a defect in biotindase results in a biotin deficiency.

51
Q

How is biotinidase diagnosed?

A

Diagnosis is by enzyme assay of biotinidase

52
Q

How is biotinidase treated?

A

Treated with biotin supplementation

53
Q

What is the defect associate with Hunter Syndrome?

A

(Lysosmal storage) Defect in iduronate-2-sulfatase, patients accumulate mucopolysaccharides such as dermatan and heparin sulfate

54
Q

How is Hunter syndrome diagnosed?

A

Diagnosed by enzyme assay of iduronidate-2-sulfatase

55
Q

What is the treatment for Hunter syndrome?

A

Can be treated by enzyme replacement thearpy (ERT) - Elaprase

56
Q

How is amonia detoxified?

A

Conversion to urea

57
Q

A patient may present with hypouricemia…

A

Lesch-Nyhan

58
Q

A patient present with hypoglycemia….

A

MCAD

59
Q

A patint can present with hyperammonemia (often due to liver damage) but never hypoammonemia…

A

MCAD

60
Q

What is the pattern of inheritance for Hunter Syndrome?

A

X-linked recessive disorder (mostly boys are affected)

MFM Week 2 (6 decks)

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