Coronary Artery Disease in Familial Hypoalphalipoproteinemia: A Case Report

Background/Synopsis

A 37-year-old Caucasian female was referred for cardiology evaluation of dyslipidemia. Her past medical history included mitral valve prolapse, Gilbert syndrome, hypertension, and aortic atherosclerosis. The patient was physically active with no history of smoking, diabetes, or other cardiovascular risk factors. Family history was notable for low HDL-C levels in the patient's father and sister, with no known premature CAD. Physical examination revealed BMI of 21, well controlled blood pressure, and normal cardiovascular exam.

Initial lipid panel revealed total cholesterol (TC) 47 mg/dL, HDL-C 5 mg/dL, LDL-C 24 mg/dL, triglycerides 80 mg/dL, and VLDL 18 mg/dL. Further laboratory testing showed apolipoprotein B of 52 mg/dL, normal lipoprotein (a), and normal high-sensitivity CRP. Liver function tests, complete blood count, thyroid function tests, total serum protein, and basic metabolic profile were also normal. Genetic testing showed 2 variants of undetermined significance to the ABCA1 gene [ABCA1 c.2879T>C (p.Leu960Pro); ABCA1 c.3626C>T (p.Pro1209Leu)].

Objective/Purpose

N/A

Methods

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Results

A coronary artery computed tomography (CTCA) demonstrated borderline obstructive areas of eccentric calcified plaque in the mid to distal left anterior descending (LAD) artery with 40-50% luminal diameter narrowing, nonobstructive eccentric calcified plaque in the proximal left circumflex (LCX) artery with less than 40% luminal diameter narrowing, and obstructive plaque in the mid right coronary artery (RCA) with greater than 50% luminal diameter narrowing, with whole-heart Agatston score of 981. A CT coronary angiography scan with fractional flow reserve (FFR) revealed a modeled stenosis in the mid RCA that demonstrated normal FFR measurement of 0.81, although was significant for abrupt relative change (.18) across the lesion. Invasive coronary angiography revealed nonobstructive coronary artery disease, demonstrating mid RCA 50% stenosis, mid LAD 40% stenosis, and ostial LCX 30% stenosis. The patient was initiated on statin and aspirin therapy. A fasting lipid profile at 2-month interval showed TC 26 mg/dL, LDL-C 5 mg/dL, and HDL-C remaining at 5 mg/dL.

Conclusions

Given ABCA1 gene variants, with absence of phenotypic findings of Tangier disease, the patient was presumed to have familial hypoalphalipoproteinemia. The inverse relationship between low HDL-C levels and cardiovascular risk has been well documented in population based observational studies. However, clinical trials have failed to show clinical benefit of therapy targeting increasing HDL-C levels. Further studies are needed to determine optimal medical therapy aimed at prevention of CAD in this population which may be genetically predisposed to higher risk of early coronary disease.