Possible explanations for the common clinical familial hypercholesterolemia phenotypes in the Faroe Islands

Background
The prevalence of clinical familial hypercholesterolemia (FH) is very high in the Faroe Islands, but the possible causes are unknown.

Objectives
We aimed to describe potential genetic causes of FH in the Faroe Islands and to investigate whether levels of lipoprotein(a) and measures of dietary habits were associated with clinical FH in the Faroe Islands.

Methods
In this case-control study, we identified potential clinical FH cases aged 18–75 years registered within a nationwide clinical laboratory database in the Faroe Islands and invited them for diagnostic evaluation according to clinical FH scoring systems. Controls were identified in the background population. Lipoprotein(a) was measured in plasma, while the fatty acid composition was determined in adipose tissue. The habitual diet of the participants was assessed using a food frequency questionnaire. Genetic testing for FH and polygenic variants was performed in a selection of clinical FH cases.

Results
A total of 121 clinical FH cases and 123 age- and sex-matched controls were recruited. We found a very low frequency of monogenic FH (2.5%), but a high level of polygenic FH (63%) in those genetically tested (67%). High levels of plasma lipoprotein(a) were associated with high odds of clinical FH. Clinical FH cases had a lower intake of saturated fatty acids (SFAs) measured by a high fat-score and a lower content of SFAs in adipose tissue compared with controls.

Conclusion
The high prevalence of FH in the Faroe Islands may be due to polygenic causes of hypercholesterolemia and to a lesser extent other genetic factors and elevated plasma lipoprotein(a) levels.