Abstract 4120854: Case Report: Elevated HDL in Familial Hyper-Alpha-Lipoproteinemia: Atheroprotective or Atherogenic?

Introduction: Familial hyper-alpha-lipoproteinemia (HALP) is a heterogenous genetic lipid disorder that is found in only 8% of the population and manifests as elevated HDL levels above the 90 th percentile. HALP is due to mutations in various genes including cholesteryl ester transfer protein (CETP), hepatic lipase, or apolipoprotein C-III (APOC3). While epidemiological studies have noted an inverse relationship between high HDL and the development of coronary artery disease, recent data have shown a lack of causal atheroprotective effects. We present a case of a patient with significantly elevated HDL and peripheral vascular disease. Case Description: Patient is a 64-year-old female with past medical history of peripheral artery disease with occlusion of the left femoral artery and popliteal arteries status post angioplasty, hypertension, type 2 diabetes, alcohol use, and CKD Stage 4 who presented to the advanced lipid clinic for management of elevated lipoproteins. Patient’s laboratory data was significant for total cholesterol (TC) of 375 mg/dL, a high-density lipoprotein (HDL) of >200 mg/dL, triglycerides (TG) of 66 mg/dL, and a low-density lipoprotein (LDL) of 175 mg/dL. Further testing revealed elevated apolipoprotein A-I of 231 mg/dL. Patient was subsequently initiated on a high intensity statin with improvement in her lipid panel with a TC of 247 mg/dL, HDL of 133 mg/dL, TG of 50 mg/dL, and LDL of 106 mg/dL, with plan for further uptitration of lipid therapy to target LDL <70 mg/dL. Discussion: CETP exchanges cholesteryl esters from HDL for TG, making HDL smaller and more TG-rich. Studies have shown that in vitro addition of CETP and hepatic lipase, which hydrolyzes phospholipids and TG, into CETP-deficient patients led to the development of very small HDL particles that were able to remove cholesterol from lipid laden macrophages. Conversely, larger HDL molecules seen in CETP-deficient patients did not have such anti-atherogenic properties. In addition to recognizing HALP in the setting of elevated HDL, it is also important to exclude secondary causes of elevated HDL, such as primary biliary cirrhosis and high-dose niacin. Genetic testing should also be considered.