Mutation screening and genotype:phenotype correlation in familial hypercholesterolaemia.

Area of Science:

• Genetics
• Molecular Biology
• Cardiovascular Medicine

Background:

• Familial hypercholesterolaemia (FH) is a genetic disorder characterized by high cholesterol levels.
• Accurate genetic diagnosis is crucial for effective management and understanding genotype-phenotype correlations.
• Existing diagnostic criteria may not fully capture all affected individuals.

Purpose of the Study:

• To develop and implement a tiered mutation screening protocol for familial hypercholesterolaemia (FH) patients.
• To investigate genotype-phenotype relationships, focusing on pre-treatment lipid profiles and tendon xanthomata (TX).
• To assess the diagnostic yield of genetic screening in families with suspected FH.

Main Methods:

• A tiered screening protocol was applied to 158 families with possible or definite FH.
• Mutation analysis focused on the low-density lipoprotein receptor (LDLR) gene and the Apo B100 gene (R3500Q).
• Genotype data were correlated with pre-treatment lipid levels and the presence of tendon xanthomata.

Main Results:

• Mutations were identified in 52 families (33%): 44 with LDLR defects and 8 with the Apo B100 R3500Q mutation.
• LDLR mutations were distributed across the gene, with a high prevalence in the LDL binding and EGF precursor homology domains.
• Frameshift mutations in LDLR were associated with the most severe clinical presentation, including higher cholesterol and increased TX incidence compared to Apo B mutations.

Conclusions:

• DNA-based diagnosis is feasible and identifies causative mutations in a significant proportion of FH families.
• Tendon xanthomata are present in only 58% of genetically confirmed FH cases, indicating limited utility as a sole diagnostic criterion.
• LDLR gene defects are associated with more severe hypercholesterolaemia and a higher incidence of TX than the common Apo B variant.