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Biochemical/Metabolic Genetics Flashcards

(60 cards)

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1
Q

Newborn Screening

A
  • heel prick done 24-48 hours after birth
  • RUSP contains 34 core and 26 secondary conditions
  • conditions added based on Wilson and Jungner criteria
  • each state free to choose own NBS panels
  • consent follows opt-out model
  • storage of dried blood spot cards varies from state to state; federally funded research requires parental consent
  • screen positive result = repeat test
  • actionable result = immediate care initiated
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2
Q

Inborn Errors of Metabolism

A
  • deficiency of enzyme prevents something from being broken down/made
  • vast majority are each rare AR conditions; consider consanguinity
  • some more common in certain ethnic groups
  • can be classified as disorders of intoxication, disorders of energy metabolism (including mitochondrial defects), or disorders involving complex molecules
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3
Q

Errors of Protein Metabolism (DI)

A
  • aminoacidopathies
  • organic acidemias
  • urea cycle defects
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4
Q

Aminoacidopathies

A
  • phenylketonuria
  • hyperphenylalaninemia
  • maternal PKU
  • tetrahydrobiopterin deficiency
  • MSUD
  • homocystinuria
  • tyrosinemia
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5
Q

Features of Aminoacidopathies

A
  • elevated amino acid level and/or immediately preceding intermediate before defect
  • neurological and behavioral impact due to build up in brain
  • vomiting, coma, liver failure, thromboembolic complications, FTT, DD, ectopia lentis, cardiomyopathy
  • symptom-free interval
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6
Q

Testing for Aminoacidopathies

A
  • plasma/serum/urine amino acid levels (high)

- enzyme activity tests (little to no activity)

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7
Q

Treatment for Aminoacidopathies

A
  • restrict substrate
  • low protein diet
  • supplement product
  • supplement cofactor
  • substitute enzyme
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8
Q

Organic Acidemias

A
  • propionic acidemia
  • methylmalonic acidemia
  • cobalamin deficiencies
  • isovaleric acidemia
  • 3-MCC deficiency
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9
Q

Features of Organic Acidemias

A
  • low blood pH levels due to build up of organic acids

- vomiting, altered mental status, lethargic, ill appearance, metabolic acidosis, hyperammonemia

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10
Q

Testing for Organic Acidemias

A
  • plasma ammonia (high)
  • venous blood gas (severe metabolic acidosis)
  • urine organic acids (acid metabolites present)
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11
Q

Treatment for Organic Acidemias

A
  • restrict amino acids preceding the organic acid
  • low protein diet
  • provide cofactor
  • provide carnitine for alternate route of elimination
  • pH stabilizer
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12
Q

Urea Cycle Defects

A
  • OTC deficiency
  • arginosuccinate lyase deficiency
  • argininemia
  • later-onset UCDs
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13
Q

Features of Urea Cycle Defects

A
  • neonatal onset

- lethargy, poor feeding, vomiting, seizures, bleeding, hyperventilation, coma, death, hyperammonemia

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14
Q

Testing for Urea Cycle Defects

A
  • ammonia levels (high)
  • arginine levels (low)
  • blood pH (no acidosis)
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15
Q

Treatment for Urea Cycle Defects

A
  • restrict substrate (essentially no protein); essential amino acid formulas
  • provide product (arginine or citrulline)
  • replace enzyme (liver transplant)
  • ammonia scavengers
  • treat secondary effects
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16
Q

Glycogen Storage Diseases

A
  • Hepatic GSDs: GSD 1a (von Gierke), GSD 1b, GSD 3, GSD 4, GSD 6, GSD 9a
  • Muscular GSDs: GSD 2 (Pompe), GSD 5 (McArdle’s), GSD 7 (Tarui)
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17
Q

Features of GSDs

A
  • glycogen stored in liver and in some muscles; some disorders affect one or other
  • accumulation of glycogen, poor feeding, lethargy, hypoglycemia
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18
Q

Testing for GSDs

A
  • not on NBS, except Pompe
  • pyruvate/lactate levels (high)
  • blood glucose (low)
  • triglycerides (high)
  • uric acid (high)
  • enzyme analysis
  • genetic testing
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19
Q

Treatment for GSDs

A
  • feed every 3 hours to prevent brain damage from lack of glucose
  • provide sugar to exercising muscle when heavily used
  • boost WBC count
  • ERT
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20
Q

Disorders of Sugar Metabolism

A
  • galactosemia (emergency)
  • hereditary fructose intolerance
  • fructose 1,6 bisphosphatase deficiency
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21
Q

Features of Sugar Metabolism Disorders

A
  • depends on condition
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22
Q

Testing for Sugar Metabolism Disorders

A
  • fructose metabolism conditions not on NBS
  • enzyme analysis
  • genetic testing
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23
Q

Treatment for Sugar Metabolism Disorders

A
  • restrict intake of offending sugar
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24
Q

Features of CDGs

A
  • infantile onset, DD, heart disease, multiorgan dysfunction, hypoglycemia, protein-losing enteropathy, skin abnormalities (peaux d’orange), neurological abnormalities (stroke-like episodes), abnormal fat distribution, death
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25
Testing for CDGs
- enzyme analysis | - genetic testing
26
Treatment for CDGs
- none
27
Fatty Oxidation Defects
- MCAD - LCHAD - VLCAD - SCAD - maternal HELLP syndrome
28
Features of FAODs
- lethargy, coma, hypoglycemia, kypoketosis
29
Testing for FAODs
- acylcarnitine profile (accumulation of fatty acid chains of different sizes)
30
Treatment for FAODs
- no fasting - high carb/low fat diet - supplement with carnitine if low
31
Disorders of the Carnitine Cycle
- carnitine uptake deficiency - CPT-1 - translocase deficiency - CPT-2
32
Features of Carnitine Cycle Disorders
- muscular weakness, cardiomyopathy, exercise intolerance. rhabdomyolysis, hypoglycemia
33
Testing for Carnitine Cycle Disorders
- acylcarnitine profile (build-up of long chain fatty acids)
34
Treatment for Carnitine Cycle Disorders
- provide levocarnitine - no fasting - low fat diet
35
Features of Peroxisomal Disorders
- elevated VLCFA
36
Testing for Peroxisomal Disorders
- not on NBS, except ALD - acylcarnitine profile (elevated VLCFA) - plasmalogen analysis (low)
37
Treatment for Peroxisomal Disorders
- management of symptoms | - BMT, hydrocortisone (ALD)
38
Muccopolysaccharidoses
- MPS I (Hurler/Scheie) - MPS II (Hunter) - MPS III (Sanfilippo) - MPS IV (Morquio) - MPS VI (Maroteaux-Lamy) - MPS VII (Sly) - MPS IX (Natowicz) - Multiple sulfatase deficiency
39
Features of MPS
- dysfunction in degradation of glycosaminoglycans (GAGs) - heparan sulfate found in ECM and has neurological effects - keratan sulfate found in bones, collagen, corneas, connective tissue - dermatan sulfate found in skin, valves, blood vessels - coarse facial features, organomegaly (hepatosplenomegaly), skeletal dysplasia, short stature, cognitive decline, progressive
40
Testing for MPS
- urine GAGs (total GAGs elevated) - enzyme analysis - genetic testing
41
Treatment for MPS
- BMT - ERT - supportive treatment
42
Sphingolipidoses
- GM1 gangliosidosis - GM2 gangliosidosis (Tay-Sachs) - Niemann-Pick A/B - Metachromic leukodystrophy - Krabbe disease - Gaucher disease - Fabry disease
43
Features of Sphingolipidoses
- defects in sphingolipid metabolism (important for neuronal cell functioning) - several AJ founder mutations - progressive neurological/cognitive decline
44
Testing for Sphingolipidoses
- not on NBS, except Krabbe - enzyme analysis (beware pseudodeficiency alleles) - urine analysis (high sulfatides for MLD) - genetic testing
45
Treatment for Sphingolipidoses
- supportive treatment - BMT (Krabbe) - ERT (Gaucher and Fabry)
46
Porphyrias
- Acute hepatic: AIP, HCP, VP, ADP | - Cutaneous: PCT (cutaneous and hepatic), CEP, EPP, XLP
47
Features of Porphyrias
- Acute hepatic: low penetrance (10-20%), women more commonly affected (80% vs 20%), abdominal pain, nausea, vomiting, pain in extremities/back, muscle weakness, anxiety, depression, dark/reddish urine, hepatocellular carcinoma, photosensitivity - Cutaneous: skin blistering, severe photosensitivity, deposition of porphyrin in skin, bones, teeth
48
Testing for Porphyrias
- urine ALA and PBG (high) - urine/plasma/fecal porphyrin levels (results depend on type) - erythrocyte protoporphyrin levels (elevated in EPP and XLP) - free:zinc-chelated erthyrocyte protoporphyrin levels (EPP, XLP) - genetic testing
49
Treatment for Porphyrias
- Acute hepatic: intravenous hemin, symptomatic relief, liver transplant, sun protection, siRNA and RNAi, avoid triggers (alcohol, smoking, stress, drugs) - Cutaneous: serial phlebotomies/hydroxychloroquinone, blood transfusions, sun/UV protection, BMT/liver transplant, melanin-producing drugs, symptomatic relief, avoid triggers
50
Conditions Involving Purine Salvage/Synthesis
- Lesch-Nyhan disease
51
Conditions Involving Cholesterol
- Niemann-Pick C - Antley-Bixler syndrome - Smith-Lemli-Opitz syndrome
52
Disorders of Carbohydrate Metabolism (DI, DEM)
- glygocen storage disorders - sugar intolerances - congenital disorders of glycosylation
53
Disorders of Fat Metabolism (DEM)
- FAODs | - carnitine cycle defects
54
Disorders of Peroxisomal Metabolism (DCM)
- peroxisomal biogenesis disorders | - adrenoleukodystrophy
55
Lysosomal Storage Disorders (DCM)
- mucopolysaccharidoses | - sphingolipidoses
56
Conditions Involving Copper Metabolism
- Menkes syndrome | - Wilson disease
57
Conditions Involving Biotin
- biotinidase deficiency
58
Neurodegeneration with Brain Iron Accumulation
- PKAN (pantothenate kinase-associated neurodegeneration) - PLAN/INAD - MPAN - BPAN - FAHN - CoPAN - KRS - ACP - NF (not neurofibromatosis)
59
Wilson and Jungner Criteria
- accurate screening test - regular review of scientific and medical rationale - significant life-challenging risk of morbidity if disorder is untreated - total costs of system from diagnosis to follow-up must be reasonably priced - significant prevalence of disorder - natural history of disease understood - consumer involvement, physician and public health acceptance in the decision to mandate screening - positive health benefits must outweigh risks and burdens - disorder must be treatable and require early treatment - resources for and access to confirmatory testing, treatment, and counseling
60
Congenital Disorders of Glycosylation
- CDG 1a

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