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MSC: Disease of major orgns > Lipid Disorders and Investigations > Flashcards

Lipid Disorders and Investigations Flashcards

1
Q

What are major classes of Lipoproteins?

A
  • —Chylomicrons
  • — Very Low Density Lipoproteins (VLDL)
  • — Intermediate Density Lipoproteins (IDL)
  • — Low Density Lipoproteins (LDL)
  • — High Density Lipoproteins (HDL)
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2
Q

What are complications from Lipoproteins?

A
  • —Increased LDL or Reduced HDL - can cause —Atheroma (CHD)
  • —Increased chylomicrons / VLDL - can lead to —Pancreatitis
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3
Q

What are secondary causes of Lipid Disorders?

A
  • Diabetes Mellitus
  • Hypothyroidism
  • EtOH
  • Nephrotic syndrome
  • CRF
  • Atypical antipsychotics
  • Cortiscosteroids
  • Oral oestogens
  • Ciclosporin
  • Beta blockers, retinoids and
  • HIV/antiretroviral drugs
  • Anabolic steroids
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4
Q

What are investigations of secondary lipid disorders to exclude secondary lipid disorders?

A
  • U+E (Na, K, urea, creatinine, eGFR) - Exclude renal failure
  • Liver profile (Tpro, Alb, ALP, ALT, GGT) - Exclude cholestasis
  • TFTs - Exclude hypothyroidism
  • HbA1c - Exclude diabetes
  • Urine Protein - Exclude nephrotic syndrome
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5
Q

What are investigations for Lipid Disorders?

A
  • Fasting lipid profile: Total cholesterol, Triglycerides, LDL cholesterol (Friedwald equation*), HDL cholesterol, Non-HDL cholesterol, Risk Ratio (TC:HDL)
  • Direct LDL
  • Apo B
  • Lipoprotein (a)
  • Apo E genotype
  • FH genotype
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6
Q

What is Friedwald equation?

A

LDL-cholesterol = Total cholesterol – HDL cholesterol – (Total triglyceride/2.19)

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7
Q

How is Familial Hypercholesteronaemia treated?

A
  • Statins (HMG CoA reductase inhibitors)
  • Ezetimibe (Bile acid sequestrants)
  • PCSK9 inhibitors
  • Apheresis
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8
Q

What is Severe Hypertriglyceridaemia?

A

Serum triglycerides often >10 mmol/L

  • Primary causes include FCS, Familial dysbetalipoproteinaemia
  • Secondary causes include diabetes and alcohol
  • Can cause Recurrent pancreatitis
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9
Q

What are physical features of Sever Hypertriglyceridaemia?

A
  • Eruptive xanthomata
  • Hepatosplenomegaly due to fat accumulation
  • Lipaemia retinalis, milky eyes (FCS)
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10
Q

What are familial Dysbetalipoproteinaemia?

A
  • Increased circulating chylomicron remnants/IDL
  • Increase in both serum cholesterol & triglyceride
  • Caused by Mutation of apoE gene – E2 phenotype
  • Low apoB concentration and apoB/total cholesterol ratio <0.15 g/mmol raises suspicion
  • Leads to accelerated atherosclerosis including peripheral arteries
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11
Q

What are physical hallmarks of Familial Dysbetalipoproteinaemia?

A
  • Palmar xanthomata
  • Eruptive xanthomata
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12
Q

What is the prevelance of Familial Hypercholesteronaemia?

A
  • —Dominantly inherited, 50% offspring affected. —Incidence approx 1 in 250 (240,000 in UK)
  • —Serum cholesterol up to 15 mmol/L
  • —15% die before 60 years
  • —50% men have MI by 50, 60% women by 60y
  • —Homozygous form is rare (1/1000000). Can lead to MI and angina in childhood. TC up to 20 mmol/L
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13
Q

What are clincal signs of Familial Hypercholesteraemia?

A

—Clinical signs in 30%:

  • Tendon xanthomata
  • Corneal arcus
  • Xanthelesma
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14
Q

What is the Simon Broome Diagnostic Criteria for Definite Familial Hypercholesteraemia?

A

—Definite Familial Hypercholesteraemia

  • —TC >7.5 mmol/L or LDL-C >4.9 mmol/L (adult)
  • —TC >6.7 mmol/L or LDL-C >4.0 mmol/L (<16y)

AND

  • —Tendon xanthomas or evidence in 1st /2nd degree relative OR
  • —DNA-based mutation in LDL-receptor, apo-B100 or PCSK9
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15
Q

What is the Simon Broome Diagnostic Criteria for Possible Familial Hypercholesteraemia?

A

Possible Familial Hypercholesteronaemia

  • —TC >7.5 mmol/L or LDL-C >4.9 mmol/L (adult)
  • —TC >6.7 mmol/L or LDL-C >4.0 mmol/L (<16y)

AND

  • —Family history of MI <50y in 2nd degree or <60y in 1st degree relative OR
  • —Family history of TC >7.5 mmol/L in 1st or 2nddegree relative
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16
Q

What are criteria for Familial Hypercholesteronamia?

A
  • Dutch Lipid Clinic Network Score
  • Simon Broome Diagnostic Criteria
17
Q

What is the cause of familial hypercholesteronaemia?

A

—Mutation affecting LDL receptor pathway (—>1000 mutations described)

—

3 genes

  • —LDL-receptor (LDLR),
  • —Apolipoprotein (apo) B100 (the LDL-receptor ligand)
  • —Proprotein convertase subtilisin/kexin type 9 (PCSK-9)
18
Q

What is Polygenic Hypercholesteronaemia?

A

Overproduction of VLDL by liver which is converted to LDL

  • Type IIa or IIb phenotype
  • Exacerbated by high fat diet and obesity
  • 12 genes tested
19
Q

What is Familial Chylomicronaemiasyndrome?

A
  • Fredrickson Type 1 (Rare, 1 in a million)
  • Autosomal Recessive, >180 mutations identified
  • Lipoprotein lipase or Co-factor deficiency: ApoA5,GPIHBP1, ApoC2 and LMF1
  • Leads to Recurrent episodes of pancreatitis
20
Q

What are physical features of Familial Chylomicronaemiasyndrome?

A
  • Eruptive xanthomata
  • Hepatosplenomegaly due to fat accumulation
  • Lipaemia retinalis
  • Milky eyes
21
Q

How is Familial Chylomicronaemiasyndrome diagnosed?

A
  • Raised Total Cholesterol and Triglycerides (3 episodes >10mmol/L)
  • Chylomicronaemia
  • Apo B < 1g/L
22
Q

What is the treatment for Familial Chylomicronaemiasyndrome?

A
  • Low fat diet

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23
Q

What is Familial Combined Hyperlipidaemia?

A
  • Incidence 1 in 100
  • Combined increase in cholesterol and triglyceride (Fredrickson type IIb)
  • Family history of premature CHD
  • No specific clinical hallmarks, but may have corneal arcus or xanthelasmata
24
Q

What are biochemical markers of Familial Combined Hyperlipidaemia?

A
  • Suspect if total cholesterol levels are in the range 6.5–10.0 mmol/L and/or triglycerides between 2.3 and 6.0 mmol/L
  • Raised VLDL and ApoB (>1.2g/L)
25
Q

What is the treatment for Familial Combined Hyperlipidaemia?

A
  • Statins - HMG CoA reductase inhibitors
  • Fibrates
  • Healthy eating pattern, lifestyle changes and weight control are also essential
26
Q

What is Abetalipoproteinaemia?

A
  • Autosomal recessive
  • Due to defect in microsomal triglyceride transfer protein (MTP) involved in assembly of TG-rich lipoproteins
  • TC <1.3 mmol/L ( almost all is HDL-C)
  • Very low serum triglycerides
27
Q

What are Abetalipoproteinaemia associated with?

A
  • Retinitis pigmentosa
  • Ataxia
  • Acanthocytes
  • Steattorrhoea
28
Q

What is Tangier’s Disease (Analphalipoproteinaemia)?

A
  • Virtual absence of HDL (apo A1 <1%, ApoA2 <5%) due to defect in ABCA1 (autosomal recessive).
  • ABCA1 is involved in efflux of cholesterol to HDL
  • Deposition of cholesterol in foam cells in Reticulo-endothelial System. enlarged orange-yellow tonsils
  • Premature atherosclerosis
29
Q

What are features of Tangier’s Disease (Analphalipoproteinaemia)?

A
  • Lymph node enlargement
  • Hepatosplenomegaly
  • Bone marrow infiltration – low platelets
30
Q

What are the phenotypes of Lipid Disorders?

A

Class I: Affects Chylomicrons

  • Normal to increased cholesterol
  • Increased Triglycerides

Class IIa: Affects LDL

  • Increased cholesterol
  • Normal Triglycerides

Class IIb: Affects LDL & VLDL

  • Increased cholesterol
  • Increased Triglycerides

Class III: Affects IDL

  • Normal to increased cholesterol
  • Increased Triglycerides

Class IV: Affects VLDL

  • Normal to increased cholesterol
  • Increased Triglycerides
31
Q

What are associated clinical disorders of phenotypes of Lipid Disorders?

A
  • Class 1: Familial chylomicronaemia syndrome (lipoprotein lipase deficiency, apolipoprotein C-II deficiency)
  • Class 2a: Familial hypercholesterolemia (1/250), Polygenic hypercholesterolemia (1/50), Nephrotic syndrome, Hypothyroidism
  • Class 2b: Familial combined hyperlipidemia(1/100)
  • Class 3: Familial Dysbetalipoproteinemia
  • Class 4: Familial hypertriglyceridemia (1/100), Familial combined hyperlipidemia, sporadic hypertriglyceridemia, Diabetes
32
Q
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MSC: Disease of major orgns (23 decks)

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