Xanthomas of the Tendon

Overview

Xanthomas of the tendon (also called tendon xanthomas) are firm, yellow‑orange nodular deposits that develop within or just under the sheath of large tendons—most commonly the Achilles tendon, the extensor tendons of the hands, and the patellar tendon. The nodules are composed of clusters of lipid‑laden macrophages (foam cells) mixed with cholesterol and other fatty substances.

These lesions are not a primary skin disease; they are a cutaneous manifestation of underlying lipid metabolism disorders, particularly familial hypercholesterolemia (FH). While tendon xanthomas can appear at any age, they are most frequently identified in children and young adults who have inherited lipid abnormalities.

Prevalence: Tendon xanthomas are relatively rare in the general population, occurring in less than 1 % of people. However, among individuals with heterozygous FH, the prevalence rises sharply—estimates range from 15 % to 30 % depending on the population studied (Mayo Clinic, 2023). In homozygous FH, nearly all patients develop tendon xanthomas before age 20.

Symptoms

Many patients first notice a painless lump; however, the full spectrum of symptoms includes:

• Visible nodules – Yellow‑orange, firm plaques that may be single or multiple, often measuring 0.5–2 cm.
• Local thickening – The affected tendon feels thicker and may be palpable even when the skin looks normal.
• Reduced range of motion – Large xanthomas on the Achilles or patellar tendon can limit ankle or knee flexion.
• Pain or tenderness – Usually only when the lesion is traumatized or inflamed; rare in early disease.
• Skin changes – Occasionally, an overlying yellowish hue or mild scaling is present.
• Systemic signs of hyperlipidemia – Early‑onset coronary artery disease (CAD), peripheral arterial disease, or family history of premature heart attacks may coexist.

In most cases, tendon xanthomas are asymptomatic beyond their cosmetic appearance, which is why they are often discovered during routine physical exams.

Causes and Risk Factors

Underlying metabolic disturbance

The primary driver is a defect in the clearance of low‑density lipoprotein (LDL) cholesterol from the bloodstream:

• Familial hypercholesterolemia (FH) – Autosomal dominant mutations in the LDLR, APOB, or PCSK9 genes cause markedly elevated LDL‑C levels.
• Homozygous FH – Two defective alleles lead to LDL‑C > 500 mg/dL and almost universal tendon xanthomas.
• Secondary hyperlipidemia – Uncontrolled diabetes, hypothyroidism, or nephrotic syndrome can raise LDL‑C enough to produce xanthomas, though this is less common.

Risk factors

• First‑degree relative with FH or early‑onset CAD.
• Elevated LDL‑C (> 190 mg/dL in adults, > 160 mg/dL in children) that is refractory to diet alone.
• Male sex – males are slightly more likely to develop palpable tendon xanthomas.
• Smoking and sedentary lifestyle – accelerate atherosclerosis and may worsen lipid profiles.

Diagnosis

Diagnosing tendon xanthomas involves a combination of clinical evaluation, imaging, and laboratory testing.

Clinical exam

A clinician will inspect and palpate the affected tendons. Classic findings are firm, non‑mobile, yellow‑orange nodules that do not blanch with pressure.

Imaging studies

• Ultrasound – Shows hyperechoic, heterogeneous masses within the tendon; useful for differentiating from cysts or tumors.
• Magnetic resonance imaging (MRI) – Provides detailed soft‑tissue contrast; tendon xanthomas appear as high‑signal lesions on T2‑weighted images with a characteristic “salt‑and‑pepper” pattern.
• Dual‑energy CT (DECT) – Can quantify calcium‑containing deposits, useful when atherosclerotic calcifications coexist.

Laboratory work‑up

• Lipid panel – Total cholesterol, LDL‑C, HDL‑C, triglycerides. LDL‑C > 190 mg/dL in adults strongly suggests FH.
• Genetic testing – Sequencing of LDLR, APOB, PCSK9 confirms FH in ~70 % of clinically suspected cases (NIH, 2022).
• Additional labs if secondary causes are suspected: TSH, fasting glucose/HbA1c, urine protein.

Diagnostic criteria

According to the Dutch Lipid Clinic Network (DLCN) scoring system, the presence of tendon xanthomas alone scores 6 points, which places a patient in the “definite FH” category when combined with other criteria.

Treatment Options

Therapy targets two goals: (1) reduce the lipid burden to prevent further xanthoma growth and cardiovascular events, and (2) address the existing lesions for functional or cosmetic reasons.

Medications

• Statins – First‑line; high‑intensity agents (atorvastatin 40‑80 mg, rosuvastatin 20‑40 mg) can lower LDL‑C by 50‑60 %.
• 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 by up to 70 % in FH patients; may even cause regression of tendon xanthomas over several years (Cleveland Clinic, 2021).
• Bile‑acid sequestrants (cholestyramine) – Useful in statin‑intolerant patients.
• Lipid apheresis – Reserved for homozygous FH or refractory cases; physically removes LDL from the bloodstream.

Procedural interventions

• Surgical excision – Indicated for large, painful xanthomas that impair tendon function; requires careful reconstruction to preserve strength.
• Laser or cryotherapy – Experimental; limited data on efficacy for tendon lesions.

Lifestyle modifications

• Adopt a heart‑healthy diet (Mediterranean or DASH): <10 % of calories from saturated fat, high in fiber, plenty of fruits, vegetables, nuts, and oily fish.
• Weight management – maintaining BMI < 25 kg/m² reduces LDL‑C modestly.
• Regular aerobic exercise (≥150 min/week) improves lipid profile and cardiovascular fitness.
• Avoid tobacco; smoking cessation improves HDL‑C and reduces atherosclerotic risk.

Living with Xanthomas of the Tendon

Daily management tips

• Skin care – Keep the overlying skin clean and moisturized; avoid tight shoes or repetitive friction over Achilles lesions.
• Physical activity – Low‑impact exercises (swimming, cycling) protect the affected tendon while still providing cardiovascular benefit.
• Regular monitoring – Schedule lipid panel checks every 3–6 months; document any change in size or tenderness of the xanthomas.
• Support shoes or orthotics – For Achilles or patellar tendon xanthomas, cushioned insoles can reduce mechanical stress.
• Psychological support – Cosmetic concerns are common; counseling or support groups can improve quality of life.

Follow‑up schedule

After the initial diagnosis:

1. First follow‑up at 1 month to assess medication tolerance.
2. Repeat lipid panel at 3 months; aim for LDL‑C < 70 mg/dL (or < 100 mg/dL if secondary prevention).
3. Imaging (ultrasound or MRI) every 1–2 years to track lesion size, unless surgical removal is performed.

Prevention

Because tendon xanthomas are a manifestation of systemic lipid imbalance, primary prevention focuses on maintaining healthy cholesterol levels.

• Screen all children with a first‑degree relative with FH at ages 2 – 10 (CDC, 2022).
• Implement family‑wide lifestyle changes; diet, exercise, and smoking cessation benefit all members.
• Start pharmacologic therapy early in genetically confirmed FH—guidelines recommend statins as early as age 8–10.
• Maintain routine cardiovascular risk assessment (blood pressure, HbA1c, BMI) to catch secondary contributors.

Complications

If left untreated, tendon xanthomas themselves can cause functional issues, but the greater danger lies in the associated lipid disorder:

• Atherosclerotic cardiovascular disease – Premature myocardial infarction, stroke, or peripheral artery disease; FH patients have a 20‑fold higher risk of early CAD.
• Tendon rupture – Large xanthomas weaken the collagen matrix, increasing the risk of spontaneous or trauma‑related tears.
• Skin ulceration – Rare, but pressure over a bulky lesion can cause breakdown.
• Psychosocial impact – Chronic visible nodules may lead to anxiety, depression, or reduced self‑esteem.

When to Seek Emergency Care

Prompt medical attention can prevent permanent damage and address life‑threatening complications.

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References:

• Mayo Clinic. “Familial hypercholesterolemia.” 2023.
• National Institutes of Health. “LDL‑C lowering therapies in FH.” 2022.
• Cleveland Clinic. “Efficacy of PCSK9 inhibitors on tendon xanthoma regression.” 2021.
• Centers for Disease Control and Prevention. “Screening recommendations for familial hypercholesterolemia.” 2022.
• World Health Organization. “Global prevalence of dyslipidemia.” 2021.