The study of familial hypercholesterolemia in Italy: A narrative review

In this review we outline our experience in the clinical and molecular diagnosis of familial hypercholesterolemia (FH), built up over more than three decades. We started our work by selecting FH patients on the basis of stringent clinical criteria, including extensive family studies. In most patients we confirmed the clinical diagnosis by showing a reduced LDLR activity in skin fibroblasts. After the isolation of LDLR cDNA and the characterization of the corresponding gene by the Dallas group, we started a systematic molecular investigation of our patients first using Southern blotting, and, subsequently Sanger sequencing. Up to now we have been able to identify 260 mutations of LDLR gene in more than 1000 genotyped FH patients, including 68 homozygotes. During this survey we identified 13 mutation clusters located in different geographical districts, which gave us the chance to compare the phenotype of patients carrying the most common mutations. We also found that mutations in APOB and PCSK9 genes were a rare cause of FH in our cohort. Despite our efforts, we failed to identify mutations in candidate genes in ∼20% of cases of definite FH. An exome-wide study, conducted within the context of an international collaboration, excluded the presence of other major genes in our unexplained FH cases. Recently, we have adopted sequencing technology of the next generation (NGS) with the parallel sequencing of a panel of FH targeted genes as a way of obtaining a more comprehensive picture of the gene variants potentially involved in the disease.