Discrimination of familial hypercholesterolemia and secondary hypercholesterolemia by achilles' tendon thickness

We examined the Achilles' tendon thickness in familial hypercholesterolemia, with and without xanthoma, and compared it with that in normal subjects and in secondary hypercholesterolemia (hypothyroidism and nephrotic syndrome). The Achilles' tendon thickness in normal subjects was 6.3 ± 0.2 mm (mean ± SEM). The thickness was significantly correlated with age and the corresponding equation was: Y (Achilles' tendon thickness in mm) = 0.044 X (age in years) + 3.77 ( r = 0.543, P < 0.01). Achilles' tendon thickness was significantly correlated with serum cholesterol and the regression equation was: Y (Achilles' tendon thickness in mm) = 0.016 X (serum cholesterol in mg/ 100 ml) + 2.94 ( r = 0.454, P < 0.01). Achilles' tendon thickness and serum triglyceride levels were not correlated ( r = 0.171, n.s.). Achilles' tendon thickness in secondary hypercholesterolemia was 6.8 ± 0.3 mm in patients with hypothyroidism and 6.6 ± 0.3 mm in nephrotic syndrome. These values were the same as those in normal subjects. Achilles'tendon thickness in familial hypercholesterolemic patients (11.8 ± 1.0 mm) was significantly greater than in those with secondary hypercholesterolemia ( P < 0.01). Achilles'tendon thickness in familial hypercholesterolemia was positively correlated with patient age ( r = 0.720, P < 0.01). The regression equation was; Y (Achilles' tendon thickness in mm) = 0.160 X (age in years) + 6.13. Thus, the measurement of Achilles' tendon thickness makes it possible to discriminate familial hypercholesterolemia from secondary hypercholesterolemia in patients whose family histories are incomplete.