Tendon Xanthomas are often categorized as being subcutaneous nodules, but they can also cause homogenous thickening of the tendons that cannot be easily detected by inspection or palpation (1)
The Achilles Tendon is a common site for TX and in fact is used as a diagnostic marker for the condition. It can have exaggerated and obvious swelling, or be very subtle. Other common sites for TX are the extensor tendons (backs) of the fingers, the plantar fascia (the bottom of the feet), and the patellar tendons surrounding the knee. They may occur soonest in areas of constant stretching, pressure and trauma.
The presence of Tendon Xanthomas is an almost certain indicator of Familial Hypercholesterolemia. Tendon Xanthomas also occur in two rare conditions, cerebrotendinous xanthomatosis and sitosterolemia, which are not easily confused with FH.