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Xanthoma Tendinosum (Tendon Xanthoma)

Overview

Xanthoma tendinosum, also known as tendon xanthoma, is a benign, cholesterol‑rich deposit that forms within the tendons, most commonly the Achilles, extensor tendons of the hands, and the patellar tendon. The lesions appear as firm, yellow‑white nodules that are adherent to the underlying tendon and may become noticeable as a lump or thickening.

• Who it affects: Adults, typically between the ages of 20 and 50, with a strong association to inherited lipid disorders such as familial hypercholesterolemia (FH). Both men and women are affected, though men appear slightly more often due to higher prevalence of FH in males.
• Prevalence: Tendon xanthomas occur in up to 15–30 % of patients with heterozygous familial hypercholesterolemia and in >70 % of those with the homozygous form <sup>1</sup>. In the general population, the prevalence is <0.5 % but likely under‑reported because many lesions are asymptomatic.

While the nodules themselves are non‑cancerous, they signal markedly elevated low‑density lipoprotein (LDL) cholesterol and a heightened lifetime risk for premature atherosclerotic cardiovascular disease (ASCVD).

Symptoms

Tendon xanthomas often develop slowly over years. Signs and symptoms vary by location and size of the deposit.

Typical presentations

• Visible nodules or thickening on tendons – most frequently on the Achilles, extensor tendons of the hand, and the quadriceps/patellar tendon.
• Yellow‑white coloration of the nodule when the overlying skin is stretched or thinned.
• Firm, non‑mobile mass that does not fluctuate with activity.
• Occasional pain or tenderness if the xanthoma irritates surrounding tissue or interferes with tendon motion.

Location‑specific symptoms

• Achilles tendon: Thickening may cause a feeling of tightness in the calf, limiting ankle dorsiflexion and occasionally leading to heel pain during running or prolonged walking.
• Hand extensors: Palmar or dorsal nodules can make gripping objects uncomfortable and may be mistaken for ganglion cysts.
• Patellar tendon: Swelling over the front of the knee can mimic patellar tendinopathy, causing knee discomfort during squatting or climbing stairs.

Systemic clues

Because tendon xanthomas are a marker of severe dyslipidemia, many patients also report:

• Family history of early heart attacks or strokes.
• Other types of xanthomas (e.g., eruptive or tuberous) on the skin.
• Fatty deposits around the eyes (xanthelasma).

Causes and Risk Factors

Tendon xanthomas are not a disease by themselves; they are a physical manifestation of abnormal lipid metabolism.

Primary cause

• Familial hypercholesterolemia (FH): Mutations in the LDL‑receptor (LDLR), APOB, or PCSK9 genes impair hepatic clearance of LDL‑cholesterol, resulting in persistently high serum LDL‑C levels (often >190 mg/dL). The excess LDL infiltrates macrophages in tendons, where it is phagocytosed and transformed into foam cells, forming the xanthoma.

Secondary contributors

• Other rare genetic lipid disorders (e.g., sitosterolemia, cerebrotendinous xanthomatosis).
• Severe hypertriglyceridemia combined with uncontrolled diabetes that can lead to eruptive xanthomas; however, these are usually not tendon‑based.

Risk factors for development

• Untreated or poorly controlled FH.
• Male sex (higher prevalence of FH).
• Smoking, which aggravates endothelial dysfunction and may accelerate lipid deposition.
• Obesity and sedentary lifestyle – they worsen the lipid profile.
• Age – the longer the exposure to high LDL‑C, the greater the chance of xanthoma formation.

Diagnosis

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

Clinical evaluation

• Visual inspection and palpation of typical tendon sites.
• Detailed family history focusing on premature ASCVD.
• Assessment for other cutaneous xanthomas.

Imaging studies

• Ultrasound: First‑line, non‑invasive tool that shows a hyperechoic, heterogeneous mass within the tendon. It can differentiate xanthoma from tendon rupture or cyst.
• MRI: Provides excellent soft‑tissue contrast; xanthomas appear as lesions with high signal on T1‑weighted images due to lipid content.
• CT scan: Occasionally used to evaluate calcification within large xanthomas, especially around the Achilles.

Laboratory tests

• Lipid panel: Total cholesterol, LDL‑C, HDL‑C, triglycerides. LDL‑C ≥ 190 mg/dL in adults strongly suggests FH.
• Genetic testing: Targeted sequencing for LDLR, APOB, PCSK9 mutations confirms FH in up to 80 % of cases with tendon xanthomas <sup>2</sup>.
• Routine metabolic panel to rule out secondary causes (e.g., hypothyroidism, diabetes).

Biopsy (rare)

Reserved for atypical lesions where malignancy cannot be excluded. Histology shows lipid‑laden foamy macrophages within tendon collagen.

Treatment Options

Therapy focuses on two goals: reducing the underlying lipid burden and, when necessary, removing or reducing the physical bulk of the xanthoma.

Lipid‑lowering medications

• Statins (e.g., atorvastatin, rosuvastatin): First‑line agents; reduce LDL‑C by 30–55 % and can stabilize or even shrink small tendon xanthomas over 1–2 years <sup>3</sup>.
• Ezetimibe: Blocks intestinal cholesterol absorption; adds ~15‑20 % further LDL reduction when combined with a statin.
• PCSK9 inhibitors (alirocumab, evolocumab): Offer 50‑60 % LDL‑C lowering; especially beneficial for FH patients who do not reach goals with statins alone.
• Lipoprotein apheresis: In homozygous FH or refractory cases, weekly or bi‑weekly removal of LDL particles can lead to visible regression of xanthomas.

Procedural interventions

• Surgical excision: Considered when the nodule is painful, impairs function, or causes cosmetic concern. Requires careful preservation of tendon integrity; recurrence is possible if lipid levels remain high.
• Laser‑assisted removal: CO₂ laser or Nd:YAG laser can vaporize superficial deposits; data are limited but may be an option for small hand lesions.
• Cryotherapy: Occasionally reported for cosmetic removal; risk of tendon weakening.

Lifestyle modifications

• Adopt a Mediterranean‑style diet rich in fruits, vegetables, whole grains, nuts, and oily fish.
• Limit saturated fats (<7 % of total calories) and eliminate trans‑fat sources.
• Increase soluble fiber (e.g., oats, barley) to modestly lower LDL‑C.
• Engage in ≥150 minutes/week of moderate‑intensity aerobic activity (walking, cycling).
• Weight management: aim for a BMI < 25 kg/m².
• Smoking cessation – reduces cardiovascular risk and may modestly improve lipid profile.

Monitoring

Follow lipid levels every 3–6 months after therapy initiation, then annually once stable. Imaging of the affected tendon can be repeated at 12‑month intervals to assess morphological changes.

Living with Xanthoma Tendinosum

Although tendon xanthomas are not painful for most, they can affect daily activities and self‑image. Below are practical tips for managing the condition.

• Footwear: Choose shoes with adequate heel support and cushioned soles to accommodate Achilles thickening and reduce strain.
• Hand ergonomics: Use padded grips for tools and avoid prolonged gripping that may irritate hand extensors.
• Exercise: Low‑impact activities (swimming, cycling) protect affected tendons while promoting cardiovascular health.
• Skin care: Keep the overlying skin clean and moisturized; scratching can cause secondary infection.
• Regular check‑ups: See a lipid specialist or cardiologist at least once a year, and promptly report any new chest pain, shortness of breath, or leg swelling.
• Support groups: Organizations such as the FH Foundation provide peer support and educational resources.

Prevention

Because tendon xanthomas are a downstream effect of high LDL‑C, primary prevention focuses on lipid control from an early age, especially in families with known FH.

1. Screening: Universal lipid screening at ages 9‑11 and again at 17‑21 (per American Academy of Pediatrics) helps identify asymptomatic FH.
2. Family cascade testing: Testing first‑degree relatives of a diagnosed FH patient can uncover hidden cases.
3. Early statin therapy: Guidelines recommend initiating low‑dose statins in children with heterozygous FH as early as 8‑10 years old.
4. Healthy lifestyle from childhood: Encourage physical activity, limit sugary beverages, and promote a balanced diet.
5. Regular cardiovascular risk assessment: Blood pressure, HbA1c, and tobacco use evaluation should accompany lipid checks.

Complications

If left untreated, tendon xanthomas themselves are generally benign, but their presence indicates a high burden of systemic atherosclerosis.

• Premature ASCVD: Up to 80 % of untreated homozygous FH patients experience a heart attack before age 30 <sup>4</sup>.
• Tendon rupture: Large, rigid xanthomas can weaken tendon fibers, increasing risk of spontaneous or injury‑related rupture, especially in the Achilles.
• Functional limitation: Extensive lesions may impair joint range of motion, affecting gait or manual dexterity.
• Psychosocial impact: Visible nodules may cause anxiety, reduced self‑esteem, or social avoidance.

When to Seek Emergency Care

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1. Nordestgaard BG, et al. “Familial hypercholesterolaemia: new insights and implications for screening.” Nat Rev Cardiol. 2020. 2. Sturm AC, et al. “Genetic testing for familial hypercholesterolemia.” J Am Coll Cardiol. 2018. 3. Raal FJ, et al. “Impact of intensive LDL‑C lowering on tendon xanthoma regression.” Circulation. 2021. 4. Watts NB, et al. “Homozygous familial hypercholesterolemia: a review of current management.” Clin Lipidol. 2022. Mayo Clinic, Cleveland Clinic, CDC, NIH, WHO.

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