Xanthelasma and tendon xanthomas: signs of cholesterol deposition
Xanthelasma (soft yellow patches on the eyelids) and tendon xanthomas (nodules on tendons) are external signs of cholesterol laid down in tissues, which can happen when blood cholesterol stays high.
Remember
Yellow eyelid patches (xanthelasma) and hard tendon nodules (tendon xanthomas) are cholesterol laid down in tissues, which can happen when LDL stays high, and the tendon nodules are the more useful clue to familial hypercholesterolaemia (FH, an inherited condition that leaves LDL cholesterol high from birth).
When blood cholesterol stays high for years (hypercholesterolaemia, a persistently high level of cholesterol in the blood), cholesterol can be laid down in tissues outside the blood vessels. Some of these deposits can be seen or felt on the surface of the body.
Xanthelasma is a set of soft yellow patches that sit on the eyelids, often close to the inner corner of the eye. It is lipid laid down in the skin.
Tendon xanthomas are deposits of cholesterol in a tendon. They feel hard, and they are painless and not tender. They appear most commonly in the Achilles tendons and over the knuckles. Another sign, corneal arcus, is a white ring around the iris (the coloured part of the eye). Like xanthelasma and tendon xanthomas, corneal arcus arises by the same process: cholesterol laid down in tissues.
In a young adult, tendon xanthomas point towards familial hypercholesterolaemia (FH). FH is inherited and is usually caused by faulty LDL receptors (docking sites on liver cells), which leave LDL cholesterol high from birth. Tendon xanthomas are highly suggestive of FH and usually appear from around 20 years of age, whereas xanthelasma and corneal arcus are less specific, so the tendon nodules are the more useful clue.
Xanthelasma is a clue, not a diagnosis, because it can also occur in people whose lipid profile is normal. A lipid profile (a test measuring cholesterol and triglycerides) is therefore the way to find out whether blood cholesterol is truly raised.
Key facts
- Xanthelasma
- soft yellow patches on the eyelids, caused by lipid deposition in the skin.
- Tendon xanthomas
- hard, painless cholesterol lumps, most commonly on the Achilles tendons and knuckles, that are highly suggestive of FH.
- Cause in FH
- usually faulty LDL receptors, which keep LDL cholesterol high from birth.
- Weaker clues
- xanthelasma and corneal arcus are less specific signs of FH.
- Not proof
- xanthelasma can occur with normal blood lipids, so a lipid profile is needed to confirm.
- Site points to lipid
- for example, tendons and eyelids point to LDL, and crops of small spots (eruptive xanthomas) point to triglyceride.
Exam traps
- A low HDL cholesterol (HDL carries cholesterol from the tissues back to the liver) does not explain cholesterol deposits in tendons, because those point to a very high LDL cholesterol.
- A very high triglyceride level can cause eruptive xanthomas, which are small yellowish spots in crops on the trunk, buttocks, elbows and knees, but they are not firm tendon nodules, so they do not account for tendon xanthomas.
- Yellow skin and yellow whites of the eyes are jaundice, which comes from a build-up of bilirubin (a yellow substance) and not from cholesterol, and which colours the whole skin instead of forming separate patches on the eyelids.
Read the full notes
Tested in 6 SimpleMed+ questions
Practice it in Metabolism, with the answer and a full explanation after every question.
Practice these questions