[Clinical and biochemical characteristics of familial ligand-defective apo B-100 in a South European population].

Background and Objective: To compare the lipoprotein phenotype between FDB and heterozygous familial hypercholesterolemia (FH); to study the prevalence and possible founder effect of familial ligand-defective apo B100 (FDB) in a Mediterranean population, and to analyze the clinical and biochemical characteristics of FDB patients.
Subjects and Method: We studied 19 heterozygous FDB subjects (8 males) from 12 related families, carriers of the R3500Q mutation on the apo B gene, and 57 heterozygous FH (24 males) genetically characterized, randomly selected from a total of 213 FH. The genetic diagnosis was established with Southern blot analysis, PCR-SSCP analysis and automatic sequencing. In all subjects, plasma lipids and apolipoprotein levels were determined with standard procedures.
Results: We demonstrated a founder effect for the R3500Q mutation in a geographically isolated rural area from our community. The prevalence of FDB in this area is high: 4/350. Heterozygous FDB subjects showed a statistical significantly lower prevalence of xanthomas and coronary heart disease, plasma concentrations of total and LDL cholesterol, HDL cholesterol, apo B and apo A-I values than heterozygous FH subjects.
Conclusions: A founder effect for the R3500Q mutation was found in a rural population with a high prevalence of FDB. In our population, FDB patients showed a mild clinical expression and lipoprotein phenotype compared with FH patients.