Tendon xanthomas (TX) are lipid deposits highly specific to familial hypercholesterolemia (FH). However, there is significant variability in their presentation among FH patients, primarily due to largely unknown causes. Lipoprotein(a) is a well-established independent risk factor for atherosclerotic cardiovascular disease in the general population as well as in FH. Given the wide variability of lipoprotein(a) among FH individuals and the likelihood that TX may result from a proatherogenic and proinflammatory condition, the objective of this study was to analyze the size of TX in the Achilles tendons of FH participants and the variables associated with their presence, including lipoprotein(a) concentration.

A cross-sectional study was conducted on 377 participants with a molecular diagnosis of heterozygous FH. Achilles tendon maximum thickness (ATMT) was measured using ultrasonography with standardized equipment and procedures. Demographic variables and lipid profiles were collected. A multivariate linear regression model using a log-Gaussian approach was used to predict TX size. Classical cardiovascular risk factors and lipoprotein(a) were included as explanatory variables.

The mean low-density lipoprotein cholesterol level was 277mg/dL without lipid-lowering treatment, and the median ATMT was 5.50mm. We demonstrated that age, sex, low-density lipoprotein cholesterol, and lipoprotein(a) were independently associated with ATMT. However, these 4 variables did not account for most the interindividual variability observed (R2=0.205).

TX, a characteristic hallmark of FH, exhibit heterogeneity in their presentation. Interindividual variability can partially be explained by age, male sex, low-density lipoprotein cholesterol, and lipoprotein(a) but these factors account for only 20% of this heterogeneity.