Severe hypercholesterolemia in four British families with the D374Y mutation in the PCSK9 gene: Long-term follow-up and treatment response

Objective - Analysis of long-term (30 years) clinical history and response to treatment of 13 patients with the D374Y mutation of PCSK9 (PCSK9 patients) from 4 unrelated white British families compared with 36 white British patients with heterozygous familial hypercholesterolemia attributable to 3 specific mutations in the low-density lipoprotein (LDL) receptor gene (LDLR) known to cause severe phenotype. Methods and Results - The PCSK9 patients, when compared with the LDLR patients, were younger at presentation (20.8±14.7 versus 30.2±15.7 years; P=0.003), had higher pretreatment serum cholesterol levels (13.6±2.9 versus 9.6±1.6 mmol/L; P=0.004) that remained higher during treatment with simvastatin (10.1±3.0 versus 6.5±0.9 mmol/L; P=0.006), atorvastatin (9.6±2.9 versus 6.4±1.0 mmol/L; P=0.006), or current lipid-lowering therapy, including LDL apheresis and partial ileal bypass in 2 PCSK9 patients (7.0±1.6 versus 5.4±1.0 mmol/L; P=0.001), and were affected >10 years earlier by premature coronary artery disease (35.2±4.8 versus 46.8±8.9 years; P=0.002). LDL from PCSK9 patients competed significantly less well for binding to fibroblast LDL receptors than LDL from either controls or LDLR patients. Conclusions - These British PCSK9 patients with the D374Y mutation have an unpredictably severe clinical phenotype, which may be a unique feature for this cohort, and requires early and aggressive lipid-lowering management to prevent cardiovascular complications. © 2005 American Heart Association, Inc.