Which Fredrickson Type corresponds to Familial Dysbetalipoproteinemia (IDL, B-VLDL)?

• A. Type I
• B. Type IIa
• C. Type IIb
• D. Type III

Answer: (D)

The key idea is that familial dysbetalipoproteinemia is defined by accumulation of remnant lipoproteins, specifically IDL (intermediate-density lipoprotein), also known as β-VLDL. This happens because clearance of chylomicron and VLDL remnants is impaired, often due to apoE abnormalities. In the Fredrickson classification, this remnant-predominant pattern is categorized as Type III. The other patterns involve different lipoprotein profiles: elevated chylomicrons alone, or elevated LDL alone or with VLDL, or elevated VLDL without remnant buildup. So, because the hallmark is increased IDL/β-VLDL remnants, the correct classification is Type III.