Familial hyperlipidaemias

Features and Fredrickson classification in order of prevalence

 MRCP  lipids  genetics

Familial hypertriglyceridaemiaFamilial combined hyperlipidaemiaFamilial hypercholesterolaemaMixed hyperlipidaemiaFamilial dysbetalipoproteinemiaType I hyperlipoproteinaemia
Hyperliproteinaemia typeIVIIbIIaVIIII
DefectIncreased VLDL production and Decreased eliminationDecreased LDL receptor and increased ApoBLDL receptor deficiencyIncreased VLDL production and Decreased LPLDefect in Apo E 2 synthesisLPL or altered ApoC2
LDL cholesterol>5 mmol/l>5 mmol/l>9 mmol/l (heterozygotes) >16 mmol/l (homozygotes)>5 mmol/lincreasednormal or reduced
Triglycerides10 - 100 mmol/l2.3 - 12 mmol/l<2.3 mmol/l>1.7 mmol/lincreasedincreased
Increased lipoproteinVLDLLDL and VLDLLDLVLDL and ChylomicronsIDLChylomicrons
InheritanceAutosomal dominantAutosomal dominantAutosomal dominantAutosomal recessiveAutosomal recessiveAutosomal recessive
Cardiovascular risknormalincreasedUnless detected earlier heterozygotes present with cardiovascular disease in their 40s, homozygotes in their teens.normal (unless metabolic syndrome associated)increasednormal
Clinical featuresCan cause pancreatitis at high triglyceride levels.Glucose intolerance, obesityXanthelasma, tendon xanthomas. Artherosclerosis.Glucose intolerance and hyperuricemia. Associated with metabolic syndrome, non-alcoholic fatty liver disease, and also polycystic Ovarian syndrome.Environmental factors important as only 1 - 4 % homozygotes develop hyperlipidaemia. Tuberous and planar xanthomata seen.Rare and managed by diet. Eruptive xanthomata and lipaemia retinalis may be seen.
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The first three columns account for 90% of cases so learn these at least.

Further reading:

https://en.wikipedia.org/wiki/Primary_hyperlipoproteinaemia

Viljoen A, Wierzbicki AS. Investigating mixed hyperlipidaemia. BMJ. 2011 Aug 25;343:d5146



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