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Xanthomatosis of the Tendons

Overview

Xanthomatosis of the tendons (also called tendon xanthoma) is a condition in which fatty‑cholesterol deposits, called xanthomas, form within or on the surface of tendons. The most common sites are the Achilles tendon, extensor tendons of the hands, and the patellar tendon. These lesions are usually firm, yellow‑orange nodules that can be felt under the skin and may cause pain or limited motion.

The condition is most often a cutaneous manifestation of familial hypercholesterolemia (FH)—a genetic disorder that markedly raises low‑density lipoprotein (LDL) cholesterol from birth. However, tendon xanthomas can also appear in secondary lipid disorders (e.g., uncontrolled diabetes, hypothyroidism, or drug‑induced hyperlipidemia).

• Who it affects: Primarily individuals with FH (heterozygous FH prevalence ≈ 1 in 250; homozygous FH ≈ 1 in 300,000) [1]. Both men and women develop tendon xanthomas, though men tend to present slightly earlier because cardiovascular risk prompts earlier lipid testing.
• Age of onset: Xanthomas rarely appear before puberty. In heterozygous FH, they typically develop in the 20s–30s; in homozygous FH, they can be present in childhood.
• Prevalence: Among people with heterozygous FH, tendon xanthomas are seen in 20–30 % of cases, while in homozygous FH >80 % develop them [2].

Symptoms

Symptoms vary according to the size and location of the deposits. Common findings include:

• Visible, yellow‑orange nodules on the skin overlying tendons (Achilles, hand extensor, patellar, or elbow).
• Firm, non‑compressible mass that can be palpated under the skin.
• Pain or tenderness when the tendon is stressed (e.g., walking, climbing stairs, gripping).
• Reduced range of motion or stiffness, especially around the ankle or fingers.
• Swelling that may fluctuate with activity or inflammation.
• Cosmetic concern – nodules are often noticeable and can affect self‑image.
• Associated cardiovascular symptoms – because tendon xanthomas are a marker of severe hypercholesterolemia, patients may have chest pain, shortness of breath, or a family history of early heart attacks.

Causes and Risk Factors

Primary cause – Familial Hypercholesterolemia (FH)

FH is caused by mutations in the LDLR, APOB, or PCSK9 genes, leading to reduced clearance of LDL‑cholesterol. Persistently high LDL (>190 mg/dL in adults) results in cholesterol deposition in vessel walls and tendons.

Secondary causes

• Uncontrolled type 2 diabetes mellitus (glycation of LDL enhances deposition).
• Hypothyroidism (elevated LDL and triglycerides).
• Nephrotic syndrome (protein loss leads to hepatic overproduction of lipoproteins).
• Cholesterol‑elevating medications (e.g., high‑dose corticosteroids, certain antiretrovirals).

Risk factors

• Genetic inheritance – autosomal dominant for heterozygous FH; autosomal recessive for homozygous FH.
• Family history of premature coronary artery disease (CAD) or tendon xanthomas.
• Male sex (slightly higher prevalence of visible lesions).
• Lifestyle that worsens lipid profile – high saturated‑fat diet, sedentary behavior, smoking.
• Obesity and metabolic syndrome.

Diagnosis

Diagnosing tendon xanthomatosis involves a combination of clinical examination, imaging, and laboratory assessment.

Clinical examination

• Inspection for yellowish nodules over typical tendon sites.
• Palpation to assess firmness and any tenderness.

Imaging studies

• Ultrasound – high‑resolution sonography shows hyperechoic, non‑compressible masses within the tendon fibers.
• Magnetic Resonance Imaging (MRI) – provides detailed soft‑tissue contrast; xanthomas appear as homogeneous, slightly hyperintense lesions on T1‑weighted images.
• CT scan – useful for surgical planning when excision is considered.

Laboratory tests

• Fasting lipid panel (LDL‑C, total cholesterol, HDL‑C, triglycerides). In FH, LDL‑C is typically >190 mg/dL (heterozygous) or >400 mg/dL (homozygous).
• Genetic testing for LDLR, APOB, PCSK9 mutations (recommended by American College of Cardiology/American Heart Association guidelines [3]).
• Secondary work‑up if FH is not confirmed: thyroid function tests (TSH, free T4), fasting glucose/HbA1c, renal function.

Diagnostic criteria (Dutch Lipid Clinic Network)

Patients are scored based on family history, clinical signs (including tendon xanthomas), LDL level, and genetic results. A score ≥8 indicates “definite FH,” 6–8 “probable FH,” and 3–5 “possible FH.” Presence of tendon xanthomas adds 6 points, heavily weighting the diagnosis.

Treatment Options

Treatment aims to (1) lower serum LDL‑cholesterol, (2) reduce the size of existing xanthomas, and (3) prevent cardiovascular complications.

Medication

• Statins (HMG‑CoA reductase inhibitors) – first‑line therapy. High‑intensity statins (e.g., rosuvastatin 20–40 mg, atorvastatin 40–80 mg) can reduce LDL by up to 55 %.
• Ezetimibe – added when statin alone is insufficient; blocks intestinal cholesterol absorption.
• PCSK9 inhibitors (alirocumab, evolocumab) – monoclonal antibodies that can lower LDL by an additional 60 % and are especially useful in homozygous FH or statin‑intolerant patients [4].
• Bile‑acid sequestrants (cholestyramine, colesevelam) – modest LDL reduction; useful as adjuncts.
• Lipid‑lowering apheresis – extracorporeal removal of LDL; reserved for severe homozygous FH or refractory cases.

Lifestyle interventions

1. Heart‑healthy diet – emphasis on fruits, vegetables, whole grains, oily fish, and plant sterols; limit saturated fat (<7 % of total calories) and trans fat.
2. Regular physical activity – at least 150 min/week of moderate‑intensity aerobic exercise.
3. Weight management – BMI 18.5–24.9 kg/m² reduces LDL modestly.
4. Smoking cessation – eliminates a synergistic risk factor for CAD.

Surgical and procedural options

• Excisional surgery – removal of large, painful, or function‑impairing xanthomas. Indicated when medical therapy fails to shrink lesions after 12–24 months.
• Liposuction‑assisted removal – minimally invasive; useful for diffuse nodules on extensor tendons.
• Laser ablation (CO₂ laser) – experimental, offers cosmetic improvement but limited data.

Recurrence after removal is possible if lipid levels remain uncontrolled.

Monitoring

Follow‑up lipid panels every 3 months until target LDL is reached, then at least annually. Imaging (ultrasound/MRI) may be repeated every 1–2 years to assess xanthoma size.

Living with Xanthomatosis of the Tendons

Beyond medical therapy, day‑to‑day strategies can improve comfort and quality of life.

• Footwear – padded, supportive shoes or orthotics reduce pressure on Achilles xanthomas and diminish pain.
• Hand ergonomics – use padded grips, ergonomic keyboards, and avoid repetitive gripping that stresses extensor tendons.
• Warm compresses – 10–15 minutes before activity may soften the tissue and lessen discomfort.
• Gentle stretching – daily calf and finger‑extensor stretches improve tendon flexibility without over‑loading the lesion.
• Regular cardiovascular screening – stress testing or coronary calcium scoring every 5 years (earlier if family history of early CAD).
• Psychosocial support – counseling or support groups for patients with visible skin lesions can address self‑esteem issues.

Prevention

Because tendon xanthomas are largely a manifestation of chronic hyperlipidemia, prevention focuses on early detection and aggressive lipid control.

1. Family screening – cascade testing of first‑degree relatives when FH is diagnosed. Children as young as 2 years can be screened if a parent has FH [5].
2. Routine lipid checks – at least once in adulthood (age 20) and earlier in high‑risk families.
3. Adopt a heart‑healthy lifestyle from childhood – balanced diet, physical activity, and avoidance of tobacco.
4. Adherence to medication – never skip statin doses; set reminders or use pill organizers.
5. Manage secondary causes – treat hypothyroidism, diabetes, and obesity promptly.

Complications

If left untreated, tendon xanthomatosis signals uncontrolled hypercholesterolemia, which carries serious downstream risks.

• Accelerated atherosclerosis – leading to premature coronary artery disease, myocardial infarction, stroke, or peripheral arterial disease.
• Tendon rupture – large, infiltrative xanthomas weaken tendon fibers, increasing the risk of spontaneous or trauma‑related tears.
• Functional impairment – limited joint motion, gait abnormalities, or hand dexterity loss.
• Cosmetic disfigurement – may cause psychosocial distress.
• Rare malignancy – although exceedingly uncommon, chronic xanthomas have been reported adjacent to atypical lipomatous tumors; any rapid change in size or pain warrants evaluation.

When to Seek Emergency Care

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References:

1. Mayo Clinic. Familial hypercholesterolemia. https://www.mayoclinic.org. Accessed June 2024.
2. Nordestgaard BG, et al. Familial hypercholesterolemia is underdiagnosed and undertreated in the general population. J Clin Lipidol. 2021;15(6):709‑720.
3. American College of Cardiology/American Heart Association. 2022 Guideline for the Management of Familial Hypercholesterolemia. https://www.acc.org.
4. Raal FJ, et al. PCSK9 inhibition in homozygous familial hypercholesterolemia: efficacy and safety of evolocumab. J Am Coll Cardiol. 2022;79(4):421‑433.
5. CDC. Cholesterol screening for children. https://www.cdc.gov. Updated 2023.

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