Xanthoma Tendinosum - Causes, Treatment & When to See a Doctor

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What is Xanthoma Tendinosum?

Xanthoma tendinosum (also called tendon xanthoma) is a benign, yellow‑orange deposit of lipid‑laden macrophages (foam cells) that forms within tendons and, occasionally, ligaments or the extensor surfaces of the hands. The most frequently affected tendons are the Achilles tendon, the extensor tendons of the hand, and the patellar tendon. Xanthoma tendinosum is most often a cutaneous marker of an underlying disorder of lipid metabolism, especially familial hypercholesterolemia (FH), but it can appear in other systemic conditions as well.

Because the lesions are situated deep to the skin and within fibrous tissue, they feel firm or rubbery and may be mistaken for nodular thickening, cysts, or even soft‑tissue tumors. Recognizing them early is important: they are a visible clue that a patient may have dangerously high low‑density‑lipoprotein (LDL) cholesterol, putting them at high risk for premature atherosclerotic cardiovascular disease (ASCVD).

Common Causes

The presence of tendon xanthomas usually signals a metabolic or systemic disorder that leads to cholesterol accumulation in macrophages. The most common causes include:

• Familial hypercholesterolemia (FH) – autosomal‑dominant mutations in the LDL‑R, APOB, or PCSK9 genes.
• Familial defective ApoB‑100 – defective binding of LDL to its receptor.
• Sitosterolemia (phytosterolemia) – excessive plant sterol absorption due to ABCG5/ABCG8 mutations.
• Homozygous hypercholesterolemia – extremely high LDL levels from birth.
• Secondary hyperlipidemia caused by uncontrolled diabetes mellitus, hypothyroidism, or nephrotic syndrome.
• Cholesterol‑raising medications such as glucocorticoids, cyclosporine, or protease inhibitors.
• Metabolic syndrome – a cluster of hypertension, central obesity, insulin resistance, and dyslipidemia.
• Lipoprotein (a) elevation – high Lp(a) can coexist with FH and contribute to xanthoma formation.
• Rare genetic lipid disorders like Tangier disease (ABCA1 deficiency) or cerebrotendinous xanthomatosis.

Associated Symptoms

While tendon xanthomas themselves are usually painless, they often appear alongside other clinical findings that signal an underlying lipid disorder:

• Cutaneous xanthomas – eruptive, tuberous, or planar lesions on the elbows, knees, buttocks, or eyelids (xanthelasma).
• Early‑onset coronary artery disease – chest pain, shortness of breath, or angina before age 45 in men and 55 in women.
• Peripheral arterial disease – claudication, leg fatigue, or cold extremities.
• Arcus cornealis – a gray‑white ring around the cornea, especially in younger patients.
• Family history of premature heart attacks or strokes.
• Joint stiffness or limited range of motion when large xanthomas compress the tendon.

When to See a Doctor

Because tendon xanthomas signal a potentially life‑threatening lipid disorder, prompt medical evaluation is recommended when any of the following are present:

• Noticeable yellow‑orange nodules on the Achilles tendon, hand extensors, or other tendons.
• Family members with known FH, early heart attacks, or similar skin lesions.
• Chest pain, shortness of breath, or unexplained fatigue, especially during exertion.
• Symptoms of peripheral arterial disease (pain while walking, leg swelling).
• Sudden vision changes or eye pain (possible arcus cornealis or retinal cholesterol emboli).
• Any new skin growth that changes rapidly in size, becomes painful, or starts to ulcerate.

Diagnosis

Evaluation combines a focused physical exam, laboratory tests, and imaging to confirm the presence of tendon xanthomas and determine the underlying cause.

1. Clinical Examination

• Inspection of tendons for yellow‑orange, firm plaques or nodules.
• Palpation to assess consistency (usually rubbery, non‑fluctuant).
• Documentation of lesion size, number, and distribution.

2. Laboratory Studies

• Lipid profile: total cholesterol, LDL‑C, HDL‑C, triglycerides.
• Genetic testing for LDL‑R, APOB, PCSK9, ABCG5/8, or other relevant mutations if FH is suspected.
• Thyroid function tests (TSH, free T4) to rule out hypothyroidism.
• Fasting glucose/HbA1c to assess diabetes.
• Liver and renal function panels if secondary causes are considered.

3. Imaging

• Ultrasound of the affected tendon – shows hyperechoic (bright) areas within the tendon substance.
• Magnetic Resonance Imaging (MRI) – provides detailed soft‑tissue contrast, helps differentiate xanthomas from tumours.
• CT or MRI of the coronary arteries (if indicated) to evaluate for atherosclerotic disease.

4. Histopathology (rarely needed)

If the diagnosis is uncertain, a core needle or excisional biopsy may be performed. Microscopy reveals foamy macrophages filled with lipid droplets, often stained with Oil‑Red O or Sudan IV.

Treatment Options

Treatment focuses on two goals: (1) reducing the underlying lipid abnormality to prevent cardiovascular events, and (2) minimizing the size of existing xanthomas for cosmetic or functional reasons.

1. Lipid‑Lowering Therapy

• High‑intensity statins (e.g., atorvastatin 40‑80 mg, rosuvastatin 20‑40 mg) – first‑line, reduce LDL‑C by 40‑55 %.
• Ezetimibe – adds ~15‑20 % LDL‑C reduction when combined with a statin.
• PCSK9 inhibitors (evolocumab, alirocumab) – can lower LDL‑C by an additional 50‑60 % and are especially useful in FH.
• Bile‑acid sequestrants – colesevelam, cholestyramine for patients who cannot tolerate high‑dose statins.
• Lipoprotein‑a‑targeted therapies such as pelacarsen in clinical development for patients with very high Lp(a).

2. Lifestyle Modifications

• Adopt a heart‑healthy diet – Mediterranean or DASH pattern, <10 % of calories from saturated fat, and limit trans fats.
• Increase soluble fiber (oats, barley, legumes) to modestly lower LDL.
• Engage in at least 150 minutes of moderate‑intensity aerobic exercise per week.
• Maintain a healthy weight (BMI 18.5–24.9 kg/m²).
• Quit smoking and limit alcohol intake.

3. Direct Management of Xanthomas

• Medical regression – many tendon xanthomas shrink by 20‑40 % after 1‑2 years of aggressive lipid‑lowering therapy.
• Surgical excision – considered for large, painful, or cosmetically distressing lesions; requires specialist referral.
• Laser therapy (e.g., CO₂ laser) – used for superficial xanthomas but less effective for deep tendon deposits.

4. Monitoring

Patients should have lipid panels checked 4–12 weeks after initiating or intensifying therapy, then every 6–12 months once goals are achieved. Imaging of tendons is rarely needed unless there is concern for growth or complication.

Prevention Tips

While genetic forms of FH cannot be “prevented,” the risk of developing tendon xanthomas and subsequent cardiovascular disease can be markedly reduced by:

• Early screening of family members (cascade testing) if a pathogenic FH mutation is identified.
• Starting lipid‑lowering therapy in childhood when FH is diagnosed – guidelines recommend statins as early as 8‑10 years old.
• Maintaining a cholesterol‑friendly diet throughout life.
• Regular physical activity and weight control.
• Controlling secondary contributors: manage diabetes, treat hypothyroidism, and avoid medications that raise LDL.
• Annual check‑ups with a primary‑care physician or lipid specialist to keep LDL‑C below 70 mg/dL (or <100 mg/dL for moderate risk) according to ACC/AHA guidelines.

Emergency Warning Signs

Although tendon xanthomas themselves are not an emergency, they can herald serious cardiovascular problems. Seek immediate medical care (call 911 or go to the nearest emergency department) if you experience:

• Sudden, severe chest pain or pressure radiating to the arm, jaw, or back (possible heart attack).
• Shortness of breath, sudden weakness, or dizziness, especially after exertion.
• Rapid, painless loss of vision or “curtain” over an eye (possible retinal artery occlusion).
• New, severe, unilateral leg pain with swelling or discoloration (possible deep‑vein thrombosis or arterial embolism).
• Sudden, unexplained collapse or loss of consciousness.

References

• Mayo Clinic. “Familial hypercholesterolemia.” Accessed March 2024. https://www.mayoclinic.org
• American College of Cardiology/American Heart Association. “2018 Guideline on the Management of Blood Cholesterol.” JACC, 2019.
• National Institutes of Health (NIH). “Statins: How do they work?” Updated 2023. https://www.nhlbi.nih.gov
• World Health Organization. “WHO Guideline on Diet, Physical Activity and Health.” 2022.
• Cleveland Clinic. “Tendon Xanthomas – What They Mean.” Accessed February 2024. https://my.clevelandclinic.org
• Raal FJ, et al. “PCSK9 Inhibitors in Familial Hypercholesterolemia.” New England Journal of Medicine, 2020.
• Griffin J, et al. “Sitosterolemia: Clinical Presentation and Management.” Journal of Lipid Research, 2021.

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