The Mysterious Question on Discordance between Achilles Tendon Thickness Assessed by Ultrasound and X-ray Has been Solved

Familial hypercholesterolemia (FH) is a hereditary disease with an autosomal dominant inheritance pattern, characterized by markedly high LDL cholesterol levels from birth and the presence of tendon xanthomas, such as in the Achilles tendon and early onset coronary artery disease 1-3) .It is a relatively common condition, affecting approximately 1 in 300 people in the general population.Because early detection can substantially reduce the risk of coronary artery disease, an accurate diagnosis is essential.The diagnosis of this condition is generally made based on clinical diagnostic criteria such as high LDL cholesterol levels and the presence of xanthomas, such as Achilles tendon thickening, in addition to family history 4) .However, relative to the measurement of LDL cholesterol levels, diagnosing xanthomas such as Achilles tendon thickening can sometimes be challenging and ambiguous, which has posed a persistent problem.In our country, the diagnosis of Achilles tendon thickening has long been made by establishing objective criteria using X-ray imaging 5) .Such clinical practice is rare worldwide, and the measurement data of Achilles tendon thickening can be considered extremely valuable.However, in recent years, in addition to X-ray imaging, ultrasound measurements have become widespread, and thickness values that serve as diagnostic criteria have been established 6) .However, relative to the reference values from X-ray imaging, there was a difference of 2 mm for both men and women (where the X-ray reference value was larger).Despite measuring the same Achilles tendon, this difference has long been a concern because of the disparity in measurement values.