Background: Familial hypercholesterolemia (FH), an autosomal dominant genetic disorder, is underdiagnosed and undertreated. The majority of FH cases are caused by low density lipoprotein receptor (LDL-R) gene mutations. The C308Y mutation in LDL-R results in approximately 70% loss of LDL-R activity, leading to the elevation of low density lipoprotein-cholesterol (LDL-C) and an increased risk of premature coronary heart disease (CHD). The aim of this study was to identify FH cases by cascade screening in family members and relatives of a 37-year old male with premature CHD and hypercholesterolemia.
Methods: Clinical exam, blood lipid profiling and genomic DNA sequencing of all exons of LDL-R were performed for the proband and his 14 family members and relatives. FH diagnosis was carried out using the Dutch Lipid Clinic Network (DLCN) criteria.
Results: Lipid profiling showed that 9 individuals, including the proband, had hypercholesterolemia. All these 9 subjects had a G > A substitution at nucleotide 986 in exon 7 resulting in the C308Y mutation as determined by DNA sequencing, and all those carrying the mutation were diagnosed as having definite FH under the DLCN criteria. However, most (7/9) did not have suggestive clinical manifestations of CHD.
Conclusions: The C308Y mutation was discovered in multiple family members and relatives for the first time in mainland China. Cascade screening is key for the confirmatory diagnosis of FH. Our hypothesis that the C308Y is a common variant in the population of Southern China origin warrants further validation by screening for the C308Y mutation in a large population.
Keywords: C308Y mutation; Cascade screening; DNA sequencing; Familial hypercholesterolemia; Low density lipoprotein receptor; Low density lipoprotein-cholesterol.