Abstract
Background:
Familial hypercholesterolemia (FH) is a common illness mainly caused by
variants occurring in the low-density lipoprotein receptor (LDLR) gene. FH is a leading cause of coronary
artery disease.
Objective:
This study aims to determine genetic defect(s) in homozygous and heterozygous FH index
patients and their first-degree blood relatives and understand the genotype-phenotype correlation.
Methods:
This study employed the genetic screening of FH-related genes by next-generation sequencing
and cascade screening by capillary sequencing.
Results:
We identified the presence of a novel frameshift variant [c.335_336insCGAG,
p.(F114Rfs*17)] and three known missense variants [c.622G>A, p.(E208K)], [c.1474G>A, p.(D492N)],
[c.1429G>A, p.(D477N)] in the LDLR gene of four unrelated Saudi families with FH. In proband 1, a
nonsense variant c.1421C>G, p.(S474*) was also detected at exon 9 of the lipoprotein lipase gene. The
segregation arrangement of the identified variants corresponded with the clinical characteristics. In this
study, all the detected variants were confined in the ligand-binding domain and epidermal growth factor
(EGF)-precursor homology domain of the LDLR protein, which portrayed severe clinical phenotypes of
FH. Moreover, these LDLR variants were in a highly conserved residue of the proteins.
Conclusion:
In addition to the finding of the novel variant in the LDLR gene that extends the spectrum
of variants causing FH, the results of this study also support the need for diagnostic screening and cascade
genetic testing of this high-risk condition and to understand the genotype-phenotype correlation,
which could lead to better prevention of coronary artery disease.