Imaging description

Thickening of the predominantly low-signal intensity Achilles tendon (Figure 69.1) is seen with a speckled or reticulated appearance on the axial fat-suppressed T1-weighted MR images. Sonography also shows thickening of the Achilles tendon, which reveals focal or diffuse hypoechoic lesions consistent with xanthoma. Sonographic lesions demonstrate discrete or confluent nodules with loss of normal tendon (fibrillar) architecture.

Importance

Tendon xanthoma is a hallmark of familial hypercholesterolemia (FH), an autosomal dominant disorder affecting about one in 500 in the general population. The patients with FH are at risk of premature coronary arterial disease due to an elevated low-density lipoprotein (LDL) cholesterol level. Early recognition and treatment of FH is important as effective treatment to lower cholesterol has been introduced. Familial hypercholesterolemia can be screened and diagnosed by the triad of tendon xanthoma, hypercholesterolemia (type IIa), and a family history of premature atherosclerosis. Physical examination may not detect up to 20% of the patients with FH after age 20. Imaging study can play an important role in such occasions by demonstrating xanthoma of Achilles tendon.

Typical clinical scenario

A patient who is suspected of having FH and whose physeal examination of Achilles tendon is unremarkable may be referred to sonographic study or MRI for the detection of xanthoma of Achilles tendon. A remote study showed a better detection of xanthoma of Achilles tendon by sonography compared with MRI for 10 patients with FH. Less commonly, characteristic appearance in MRI may lead to the diagnosis of FH in whom such diagnosis has not been suspected. The extensor tendons of the fingers and patellar tendons are other common sites for development of xanthoma.