What is the difference between dyslipidemia and hyperlipidemia?

Difference Between Dyslipidemia and Hyperlipidemia

Dyslipidemia is a broader term that encompasses any abnormality in lipid metabolism, including elevated lipid levels, decreased lipid levels, or abnormal composition of lipoproteins, while hyperlipidemia specifically refers to elevated levels of lipids in the blood, particularly total cholesterol, LDL cholesterol, or triglycerides. 1, 2

Definitions and Distinctions

Dyslipidemia

• Refers to a disorder of lipoprotein metabolism that can manifest as:
  • Elevations in total cholesterol, LDL-C, non-HDL-C, or triglycerides
  • Decreased levels of HDL-C
  • Abnormal composition or function of lipoproteins (e.g., small dense LDL particles)
  • Any combination of these abnormalities 1

Hyperlipidemia

• Specifically refers to elevated levels of lipids in the blood:
  • Hypercholesterolemia: Elevated LDL cholesterol ≥130 mg/dL and total cholesterol ≥200 mg/dL
  • Hypertriglyceridemia: Elevated triglyceride levels ≥150 mg/dL 2, 3

Classification and Types

Types of Dyslipidemia

1. Primary (genetic) dyslipidemia:

   • Familial Hypercholesterolemia (FH): Characterized by very high LDL-C levels (≥190 mg/dL)
   • Familial Combined Hyperlipidemia (FCH): Multiple phenotypes within families
   • Familial Hypertriglyceridemia (FHTG)
   • Lipodystrophy: Loss of adipose tissue associated with hypertriglyceridemia 1

2. Secondary dyslipidemia:

   • Caused by underlying medical conditions:
     • Diabetes mellitus
     • Obesity and insulin resistance
     • Hypothyroidism
     • Chronic kidney disease
     • Liver disease
     • HIV-associated lipodystrophy 1
   • Medication-induced:
     • Corticosteroids
     • Antiretroviral therapies
     • Immunosuppressants 1

Types of Hyperlipidemia (Fredrickson Classification)

1. Type I: Elevated chylomicrons and triglycerides
2. Type IIa: Elevated LDL cholesterol
3. Type IIb: Elevated LDL and VLDL
4. Type III: Elevated IDL (intermediate density lipoprotein)
5. Type IV: Elevated VLDL and triglycerides
6. Type V: Elevated chylomicrons, VLDL, and triglycerides 3

Clinical Significance and Patterns

Dyslipidemia Patterns

• Diabetic dyslipidemia: Characterized by elevated triglycerides, decreased HDL-C, and qualitative changes in LDL particles (small, dense LDL) despite potentially normal LDL-C levels 1
• Metabolic syndrome dyslipidemia: Similar pattern to diabetic dyslipidemia, often with central obesity 1
• HIV-associated dyslipidemic lipodystrophy: Characterized by increased triglycerides in VLDL, LDL, and HDL due to reduced clearance of triglyceride-rich lipoproteins 1

Hyperlipidemia Focus

• Primarily focuses on quantitative increases in lipid levels
• Treatment thresholds are typically based on specific cutoff values (e.g., LDL-C ≥130 mg/dL) 2, 3

Clinical Implications

Risk Assessment

• Both conditions increase cardiovascular risk, but dyslipidemia provides a more comprehensive assessment by considering:
  • Lipoprotein composition and function
  • HDL levels and functionality
  • Triglyceride metabolism 1, 2

Treatment Approach

• For hyperlipidemia: Treatment focuses primarily on lowering elevated lipid levels to below specific thresholds
• For dyslipidemia: Treatment addresses the overall lipid profile, including:
  • Lowering elevated lipids
  • Raising low HDL-C when appropriate
  • Improving lipoprotein composition and function 1, 2, 4

Common Pitfalls and Caveats

1. Focusing only on LDL-C levels: While elevated LDL-C is important, other lipid abnormalities like low HDL-C or elevated triglycerides significantly contribute to cardiovascular risk.

2. Overlooking secondary causes: Always consider underlying conditions (diabetes, hypothyroidism, kidney disease) that may cause or exacerbate dyslipidemia before initiating treatment.

3. Ignoring non-HDL cholesterol: Non-HDL cholesterol (total cholesterol minus HDL-C) is an important target, especially in patients with elevated triglycerides.

4. Misinterpreting normal LDL-C: Patients with normal LDL-C may still have dyslipidemia due to low HDL-C, high triglycerides, or abnormal lipoprotein composition (small, dense LDL particles).

5. Overlooking fasting status: Triglyceride levels are significantly affected by recent food intake, so fasting status should be considered when interpreting lipid profiles 1, 2.