A patient presents with elevated total cholesterol, subcutaneous xanthomas, and a positive family history of similar findings. Triglyceride levels are normal (<140 mg/dL). What is the most likely type of familial dyslipidemia?

Correct Answer: C. Type IIa

Type IIa familial hypercholesterolemia (FH) is characterized by isolated elevation of LDL cholesterol with normal triglyceride levels, making it the most likely diagnosis in this patient. The clinical triad—elevated total cholesterol, subcutaneous xanthomas (lipid deposits in tendons and skin), and positive family history—is pathognomonic for FH. The discriminating feature here is the normal triglyceride level (<140 mg/dL), which rules out Type IIb (which has elevated triglycerides) and Type I (which presents with severe hypertriglyceridemia and eruptive xanthomas, not subcutaneous xanthomas). Type IIa results from defects in the LDL receptor gene (most common, ~90% of FH cases in India) or apoB-100 mutations, leading to impaired LDL clearance and accumulation. Subcutaneous xanthomas appear in tendons (Achilles, extensor digitorum) and are pathognomonic for chronic LDL elevation. The heterozygous form affects 1 in 500 Indians and carries significant cardiovascular risk; homozygous FH (1 in 1 million) presents earlier with more severe manifestations. Indian guidelines recommend statin therapy as first-line, with LDL targets <100 mg/dL (or <70 mg/dL if CAD present). The normal triglyceride level is the key discriminator that excludes all other types.

Why the other options are wrong

A. Type IIb — Type IIb (familial combined hyperlipidemia) presents with elevated cholesterol AND elevated triglycerides (typically >200 mg/dL). This patient has normal triglycerides, ruling out Type IIb. Type IIb is caused by overproduction of VLDL and is more common in India than Type IIa; however, the normal triglyceride level here is the discriminating feature that excludes it. NBE trap: students may confuse 'Type II' variants and forget that IIb requires hypertriglyceridemia. B. Type I — Type I (familial chylomicronemia) is caused by lipoprotein lipase deficiency and presents with severe hypertriglyceridemia (>1000 mg/dL), eruptive xanthomas (small, yellow papules on buttocks/elbows), lipemic plasma, and recurrent pancreatitis. This patient has normal triglycerides and subcutaneous (not eruptive) xanthomas, making Type I incompatible. Type I is rare in India but often tested because of its dramatic presentation. D. Type II — Option D ('Type II') is ambiguous nomenclature—it may refer to the broader category encompassing both IIa and IIb. However, in NEET PG, 'Type II' without a suffix typically implies Type IIb in the context of familial dyslipidemia classification. Since this patient has normal triglycerides, Type IIb is excluded. The specific answer 'Type IIa' is more precise and clinically accurate for isolated LDL elevation with normal triglycerides.

High-Yield Facts

Mnemonics

FH Types by Lipid Profile Type I: Chylo ↑↑↑ (TG >1000) | Type IIa: LDL ↑, TG normal | Type IIb: LDL ↑, TG ↑ | Type III: IDL ↑ | Type IV: VLDL ↑ (TG ↑) | Type V: Chylo + VLDL ↑ (TG >1000). Use: Quickly identify which type based on TG level—if TG normal, think IIa; if TG high, think IIb or I. Xanthoma Type Clue Subcutaneous/Tendon xanthomas → chronic LDL elevation (IIa/IIb) | Eruptive xanthomas → severe TG elevation (I/V) | Palmar xanthomas → Type III. Use: When you see 'subcutaneous xanthomas,' immediately think IIa with normal TG.

NBE Trap

NBE pairs 'familial dyslipidemia' with 'xanthomas' to lure students into choosing Type I (eruptive xanthomas) or Type IIb (common in India). The trap: students forget that subcutaneous xanthomas + normal triglycerides = Type IIa, not the more common Type IIb. The normal TG level is the key discriminator.

Clinical Pearl

In Indian clinical practice, heterozygous Type IIa FH is often missed because patients present with premature MI (age 35–45) without obvious risk factors. Screening first-degree relatives and aggressive statin therapy (target LDL <70 mg/dL) can prevent 50% of cardiovascular events. Always check family history and lipid profile in young MI patients—FH is underdiagnosed in India.

_Reference: KD Tripathi Ch. 31 (Lipid-Lowering Drugs); Robbins Ch. 5 (Genetic Disorders); Harrison Ch. 395 (Lipoprotein Disorders)_