Xanthoma of the Tendon

What is Xanthoma of the Tendon?

A xanthoma of the tendon (also called a tendon xanthoma) is a firm, yellow‑orange nodule that forms within or on the surface of a tendon, most commonly the Achilles, extensor tendons of the hand, or the patellar tendon. These nodules are composed of collections of lipid‑laden (cholesterol‑filled) macrophages called foam cells that accumulate in the connective tissue of the tendon. Xanthomas are not cancerous, but their presence often signals an underlying disorder of lipid metabolism, especially familial hypercholesterolemia (FH). Because the lesions can be painless and grow slowly, many patients first notice a “bump” on the back of the ankle or the palm and are unaware of its systemic significance.

Common Causes

Although tendon xanthomas are most strongly linked to genetic lipid disorders, several other conditions can produce similar lesions.

• Familial hypercholesterolemia (FH) – autosomal‑dominant mutation in the LDL‑receptor, APOB, or PCSK9 genes.
• Familial combined hyperlipidemia – elevations of LDL‑C and triglycerides.
• Type IIa hyperlipoproteinemia – isolated LDL‑C elevation.
• Type III dysbetalipoproteinemia – defective ApoE leading to remnant‑particle buildup.
• Secondary hypercholesterolemia – caused by uncontrolled diabetes, hypothyroidism, or nephrotic syndrome.
• Cholesterol‑lowering medication intolerance – prolonged periods without lipid‑lowering therapy can allow xanthoma formation.
• Familial sitosterolemia – rare plant‑sterol absorption disorder that raises plant sterol levels.
• Acquired lipid disorders after organ transplantation – immunosuppressive drugs (e.g., cyclosporine, steroids) can raise LDL‑C.
• Metabolic syndrome – combination of obesity, hypertension, and dyslipidemia may predispose to xanthomas.
• Rare infiltrative diseases – such as Erdheim‑Chester disease, which can produce foamy macrophage deposits in tendon tissue.

Associated Symptoms

Tendon xanthomas themselves are usually painless, but they often coexist with other clinical findings that reflect the underlying lipid disorder.

• Yellowish papules or plaques on the elbows, knees, or buttocks (eruptive or plane xanthomas).
• Corneal arcus – a gray‑white ring around the cornea, especially in younger patients.
• Premature atherosclerotic cardiovascular disease – angina, myocardial infarction, or stroke before age 55 (men) or 65 (women).
• Family history of early heart attacks or hypercholesterolemia.
• Occasional tenderness or slight limitation of tendon movement if the nodule is large.

When to See a Doctor

Because tendon xanthomas are a visible clue to a serious metabolic problem, prompt evaluation is important. Seek medical attention if you notice any of the following:

• A new, firm, yellow‑orange lump on a tendon that does not resolve within a few weeks.
• Multiple xanthomas (on hands, elbows, knees, feet) in addition to the tendon nodule.
• Personal or family history of early heart disease, stroke, or high cholesterol.
• Pain, swelling, or limitation of motion at the site of the nodule.
• Skin changes such as eruptive xanthomas (tiny yellow papules) that appear suddenly.
• Any new cardiovascular symptoms (chest pain, shortness of breath, unexplained fatigue).

Diagnosis

Diagnosis involves a combination of clinical examination, laboratory testing, imaging, and, rarely, tissue sampling.

1. Clinical Examination

• Visual inspection of the nodule’s color, size, and consistency.
• Palpation to assess firmness and adherence to the tendon.
• Full skin survey for other xanthomas or corneal arcus.
• Family history and cardiovascular risk assessment.

2. Laboratory Tests

• Lipid panel – total cholesterol, LDL‑C, HDL‑C, triglycerides.
• Genetic testing for FH (LDLR, APOB, PCSK9) if lipid levels are markedly elevated.
• Thyroid function tests, fasting glucose, and urine protein to rule out secondary causes.

3. Imaging Studies

• Ultrasound – shows a hyperechoic, heterogeneous mass within the tendon; helpful for measuring size.
• Magnetic resonance imaging (MRI) – provides detailed anatomy, especially if the lesion interferes with tendon function.
• Computerized tomography (CT) or coronary calcium scoring – often ordered concurrently to assess atherosclerotic burden in high‑risk patients.

4. Histopathology (rarely needed)

If the diagnosis is uncertain, a small punch or excisional biopsy can be performed. Microscopic examination reveals lipid‑filled foam cells, cholesterol clefts, and a fibrous stromal background. The findings confirm a xanthoma and exclude malignancy.

Treatment Options

Therapy is two‑pronged: (1) address the underlying lipid disorder to halt further xanthoma growth, and (2) manage the existing tendon lesion if it causes functional problems or cosmetic concern.

1. Lipid‑Lowering Strategies

• Statins (e.g., atorvastatin, rosuvastatin) – first‑line agents that lower LDL‑C by 30‑50 %.
• Ezetimibe – blocks intestinal cholesterol absorption; adds 15‑20 % LDL‑C reduction when combined with a statin.
• PCSK9 inhibitors (evolocumab, alirocumab) – monoclonal antibodies that can reduce LDL‑C >60 % and are especially useful in FH.
• Bile‑acid sequestrants (cholestyramine) – modest LDL‑C lowering; useful when statins are not tolerated.
• Lipoprotein apheresis – extracorporeal removal of LDL‑C for severe, refractory FH.

Achieving LDL‑C < 70 mg/dL (or < 55 mg/dL in very high‑risk patients) is the goal recommended by the American College of Cardiology/AHA guidelines.¹

2. Direct Management of the Tendon Nodule

• Observation – many small, asymptomatic lesions shrink spontaneously after aggressive lipid control.
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• Intralesional corticosteroid injection – sometimes used to reduce local inflammation, though evidence is limited.
• Surgical excision – indicated for large, painful nodules that limit tendon function or cause cosmetic distress. Post‑operative recurrence is low if LDL‑C is well‑controlled.
• Physical therapy – gentle stretching and strengthening can maintain range of motion while the lesion resolves.

3. Lifestyle Modifications

• Adopt a heart‑healthy diet: Mediterranean or DASH patterns, < 30 g of saturated fat daily, limit trans fats.
• Increase soluble fiber (oats, barley, legumes) to aid cholesterol excretion.
• Engage in at least 150 minutes of moderate aerobic activity per week.
• Maintain a healthy weight (BMI < 25 kg/m²) and quit smoking.

Prevention Tips

Because most tendon xanthomas arise from untreated or undertreated hyperlipidemia, primary prevention focuses on early detection and aggressive lipid management.

• Screen cholesterol levels at least once in adulthood; start earlier (ages 9‑11) if there is a family history of FH.
• Use cascade screening for first‑degree relatives of anyone diagnosed with FH.
• Adhere strictly to prescribed lipid‑lowering medication; never stop without a clinician’s guidance.
• Follow a diet low in saturated fat and high in plant sterols (e.g., fortified margarine).
• Stay physically active – regular exercise can raise HDL‑C and lower triglycerides.
• Control secondary contributors: keep blood pressure, blood glucose, and thyroid function within target ranges.
• Attend regular cardiovascular follow‑up; repeat lipid panels every 3‑12 months depending on risk.

Emergency Warning Signs

References

1. American College of Cardiology/American Heart Association. 2023 Guideline on the Management of Blood Cholesterol. Circulation. 2023;147:e285‑e350.
2. Mayo Clinic. Tendon xanthoma. https://www.mayoclinic.org/diseases-conditions/tendon-xanthoma/symptoms-causes/syc-20353657 (accessed June 2026).
3. National Institutes of Health. Familial Hypercholesterolemia. https://ghr.nlm.nih.gov/condition/familial-hypercholesterolemia (accessed June 2026).
4. Cleveland Clinic. Xanthomas: What They Are and What They Mean. https://my.clevelandclinic.org/health/diseases/21525-xanthomas (accessed June 2026).
5. World Health Organization. WHO Guideline on Pharmacological Management of Dyslipidaemias. 2022.