Ultrasonographic Assessment of Achilles Tendon Thickness in Pediatric Patients with Suspected Familial Hypercholesterolemia

Background: Achilles tendon (AT) thickening reflects cumulative low-density lipoprotein cholesterol (LDL-C) exposure. The Japan Atherosclerosis Society (JAS) explicitly includes AT thickness as a diagnostic criterion for familial hypercholesterolemia (FH) in adults, whereas internationally, it is not a standard diagnostic measure. However, the clinical significance of AT thickening in pediatric populations remains unclear. Methods: We conducted a single-center, retrospective, observational study involving pediatric patients (11–18 years old) with suspected FH through standardized universal lipid screening across Kagawa Prefecture, Japan. Genetic testing confirmed FH through pathogenic variants in the LDLR, PCSK9, or APOB genes. The AT thickness was measured using a standardized ultrasonography protocol. We assessed associations between the FH status, cumulative LDL-C levels, and AT thickness. Results: In the pediatric patients, no significant difference in the AT thickness was observed between the FH and non-FH groups (median 4.4 vs. 4.5 mm; p = 0.570). Cumulative LDL-C was higher in the FH group, while no clear association between cumulative LDL-C and AT thickness was apparent in either group. Conclusions: In this single-center, retrospective study of pediatric patients identified through standardized universal lipid screening, no significant differences were found in AT thickness between FH and non-FH groups although cumulative LDL-C levels were higher in the FH group. Given methodological limitations (small sample size, selection bias, and residual confounding related to statin therapy and growth), these findings should be interpreted as exploratory rather than confirmatory. Regardless of genotype, early risk management may be warranted.