Biochemistry · Topic
Fredrickson classification of hyperlipoproteinaemias !
The Fredrickson system sorts high blood fats into five types by which lipoprotein particle is raised. Each type points to typical causes and risks.
Updated 2026-11-01
Key facts
- Type I: chylomicrons ↑ (LPL or ApoC-II deficiency); very high triglycerides, pancreatitis, eruptive xanthomas, lipaemia retinalis; little atherosclerosis.
- Type IIa: LDL ↑ (familial hypercholesterolaemia: LDL receptor, ApoB or PCSK9); tendon xanthomas and early coronary disease. Type IIb: LDL and VLDL ↑ (familial combined hyperlipidaemia).
- Type III: remnants/IDL ↑ (familial dysbetalipoproteinaemia, ApoE2/E2); cholesterol and triglycerides both high, palmar and tuberoeruptive xanthomas, 'broad β band'.
- Type IV: VLDL ↑ (familial hypertriglyceridaemia and secondary causes: obesity, diabetes, alcohol); the most common phenotype.
- Type V: VLDL and chylomicrons ↑; severe hypertriglyceridaemia with risk of acute pancreatitis.
In detail
- 1. It is based on the pattern of lipoproteins seen by electrophoresis and ultracentrifugation (adopted by WHO in 1970), not on genes.
- 2. The same phenotype can come from different gene defects, and one family can show different types (for example IIa, IIb and IV in familial combined hyperlipidaemia).
- 3. Refrigerator test: a creamy top layer = chylomicrons (types I and V); a turbid whole sample = VLDL (types IV and V); clear plasma = LDL (type IIa).
- 4. Secondary causes must be ruled out first: diabetes, hypothyroidism, nephrotic syndrome, cholestasis, alcohol, obesity and drugs (corticosteroids, oestrogens, thiazides, some antiretrovirals, retinoids).
- 5. It does not include low HDL or high lipoprotein(a), so treatment decisions today rely on LDL cholesterol, triglycerides, apoB and total cardiovascular risk.
- 6. Triglycerides above about 1,000 mg/dL (11 mmol/L) carry a high risk of pancreatitis whatever the type.
Memory aid
Type I = one particle (chylomicron); type IIb = IIa + IV (LDL + VLDL); type V = I + IV (chylomicrons + VLDL).
- Also called
- WHO/Fredrickson types I–V, Primary hyperlipoproteinaemias
Clinical notes
- Tendon xanthomas suggest type IIa; palmar crease xanthomas suggest type III; eruptive xanthomas suggest types I or V.
- Hypothyroidism is a classic secondary cause of high LDL; it should be checked before starting lipid-lowering drugs.
- Types I and V are emergencies when triglycerides are very high, because of acute pancreatitis.
Related conditions
- Familial chylomicronemia syndrome (lipoprotein lipase deficiency)
- Familial hypercholesterolemia
- Familial dysbetalipoproteinemia (type III hyperlipoproteinemia)
- Familial combined hyperlipidaemia
- Familial hypertriglyceridaemia
- Atherosclerosis and dyslipidaemia
- Acute pancreatitis
- Hypothyroidism
Related
- Lipoprotein metabolism
- Chylomicron
- VLDL (very-low-density lipoprotein)
- LDL (low-density lipoprotein)
- HDL (high-density lipoprotein)
- Lipoprotein lipase (LPL)
- LDL receptor
- Apolipoprotein E (ApoE)
- Apolipoprotein B (ApoB-100 and ApoB-48)
- PCSK9
- Centrifugation and ultracentrifugation
- Plasma proteins and electrophoresis
Test yourself
Think of the answer, then tap the question to see it.
Which Fredrickson type is caused by lipoprotein lipase or ApoC-II deficiency?
Type I (raised chylomicrons), with very high triglycerides and risk of pancreatitis.
Which lipoproteins are raised in type IIb?
LDL and VLDL, as in familial combined hyperlipidaemia.
Which xanthoma suggests type III, and what genotype causes it?
Palmar crease xanthomas (xanthoma striata palmaris); usually ApoE2/E2 homozygosity with a second hit.
What is the most common Fredrickson phenotype and what is raised?
Type IV, with raised VLDL, often worsened by obesity, diabetes or alcohol.
What does a creamy layer on refrigerated plasma indicate?
Chylomicrons, as in types I and V.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Familial combined hyperlipidemia: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Familial hypertriglyceridemia: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Familial hypercholesterolemia: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); High blood cholesterol levels: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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Representative model, for educational purposes only.