```html

Tendon Xanthoma (Xanthomas of the Tendons) – A Comprehensive Medical Guide

Overview

Tendon xanthomas are firm, yellow‑orange nodules that develop within tendons, most commonly the Achilles tendon, extensor tendons of the hands, and the patellar tendon. They are deposits of cholesterol‑rich macrophages (foam cells) and are considered a cutaneous manifestation of an underlying lipid disorder, especially familial hypercholesterolemia (FH).

While tendon xanthomas are relatively rare in the general population, they are found in up to 20–30 % of individuals with heterozygous FH and in more than 80 % of those with the homozygous form — making them an important clinical clue for early detection of severe hypercholesterolemia.<sup>[1]</sup> They can appear at any age, but the median age of onset is in the late teens to early 30s, often before atherosclerotic cardiovascular disease becomes symptomatic.

Symptoms

The primary feature of tendon xanthomas is the nodule itself, but patients may notice additional signs that help differentiate them from other soft‑tissue masses.

• Firm, yellow‑orange or pinkish nodules embedded within a tendon; they are usually non‑painful and immobile.
• Location‑specific patterns:
  • Achilles tendon – the most common site; may cause a feeling of “tightness” or reduced ankle flexibility.
  • Extensor tendons of the fingers – especially the middle and distal phalanges; may produce a “knobby” appearance of the fingers.
  • Patellar tendon – can be felt just below the kneecap.
• Gradual enlargement over months to years; the nodules can coalesce, forming larger plaques.
• No inflammation (no redness, warmth, or swelling); differentiates from tendinitis or infection.
• Associated lipid‑related signs such as corneal arcus, xanthelasma (eyelid plaques), or tuberous xanthomas on elbows/knees.
• Possible functional limitation if the nodule is large enough to impair tendon glide, leading to reduced range of motion or mild pain during activity.

Causes and Risk Factors

Tendon xanthomas are not a primary disease; they result from an underlying disorder of lipid metabolism.

Primary Causes

1. Familial Hypercholesterolemia (FH) – an autosomal dominant mutation in the LDLR, APOB, or PCSK9 genes that impairs LDL‑receptor function, leading to markedly elevated LDL‑cholesterol.
2. Rare lipid disorders such as sitosterolemia, cerebrotendinous xanthomatosis, and familial combined hyperlipidemia can also produce tendon xanthomas.

Risk Factors

• First‑degree relative with FH or known tendon xanthomas.
• Serum LDL‑C > 190 mg/dL (≥ 4.9 mmol/L) without treatment.
• Early‑onset coronary artery disease (CAD) in the family (e.g., myocardial infarction before age 55 in men or 65 in women).
• Presence of other xanthomatous lesions (corneal arcus, xanthelasma, tuberous xanthomas).
• Male sex – FH tends to manifest clinically earlier in men.
• Ethnicity: Certain populations (e.g., French‑Canadian, South African Afrikaner) have higher carrier frequencies for FH mutations.

Diagnosis

Diagnosis is a two‑step process: recognizing the physical lesion and confirming the underlying lipid abnormality.

Clinical Examination

• Visual inspection and palpation of tendons for characteristic yellow‑orange, firm, subcutaneous nodules.
• Measurement of nodule size with a ruler or caliper; documentation of location.
• Screening for other xanthomatous lesions and assessment of cardiovascular risk.

Imaging Studies

1. Ultrasound – readily available; shows a hyperechoic, non‑compressible mass within the tendon sheath.
2. Magnetic Resonance Imaging (MRI) – provides detailed soft‑tissue contrast; tendon xanthomas appear as fusiform thickening with intermediate signal on T1 and T2 sequences.
3. CT Scan – occasionally used to assess calcification, but radiation exposure limits routine use.

Laboratory Evaluation

• Fasting lipid panel: LDL‑C, total cholesterol, HDL‑C, triglycerides.
• Genetic testing for FH (sequencing of LDLR, APOB, PCSK9) if clinical suspicion is high.
• Secondary causes of hyperlipidemia (thyroid panel, renal function, liver enzymes, glucose/HbA1c) to rule out contributing factors.

Diagnostic Criteria

The Dutch Lipid Clinic Network (DLCN) score combines clinical findings, lipid levels, and genetic results to categorize FH probability (definite, probable, possible, unlikely). Tendon xanthomas add 6 points, strongly weighting the score toward a definitive FH diagnosis.<sup>[2]</sup>

Treatment Options

Management targets two goals: reducing the size/impact of the xanthoma and, more importantly, lowering LDL‑C to prevent cardiovascular events.

Pharmacologic Therapy

• Statins (HMG‑CoA reductase inhibitors) – first‑line; lower LDL‑C by 30–50 %.<sup>[3]</sup>
• Ezetimibe – added if LDL‑C goal not reached; inhibits intestinal cholesterol absorption.
• PCSK9 inhibitors (evolocumab, alirocumab) – monoclonal antibodies that can reduce LDL‑C by up to 60 % and have been shown to regress tendon xanthomas in some patients.<sup>[4]</sup>
• Bile‑acid sequestrants, lomitapide, mipomersen – reserved for homozygous FH or refractory cases.

Procedural & Surgical Options

• Excisional surgery – removal of the nodule; considered when the lesion causes functional limitation, pain, or cosmetic concern. Recurrence is possible if lipid levels remain uncontrolled.
• Laser‑assisted therapy – limited data; primarily used for superficial xanthomas, not tendons.

Lifestyle Modifications

1. Diet – adopt a heart‑healthy diet (Mediterranean or DASH), emphasizing soluble fiber, plant sterols, and limiting saturated/trans fats.
2. Physical activity – regular aerobic exercise (150 min/week) improves lipid profile and cardiovascular health.
3. Weight management – achieving a BMI < 25 kg/m² when possible.
4. Smoking cessation – smoking magnifies cardiovascular risk in FH.
5. Alcohol moderation – excess alcohol can raise triglycerides.

Living with Xanthomas of the Tendons (Tendon Xanthoma)

Because tendon xanthomas are chronic lesions, long‑term self‑care is essential.

• Regular follow‑up – see a lipid specialist every 3–6 months until LDL‑C goals are achieved; then at least yearly.
• Self‑examination – monthly checks of tendons for growth or new nodules; photograph lesions to track changes.
• Footwear selection – for Achilles tendon involvement, choose shoes with good heel support and avoid activities that place excessive strain (e.g., aggressive running).
• Physical therapy – gentle stretching and strengthening can maintain tendon flexibility without aggravating the xanthoma.
• Family screening – first‑degree relatives should have lipid panels and clinical exam; early detection saves lives.

Prevention

While the genetic predisposition cannot be altered, the expression of tendon xanthomas can be markedly reduced by aggressive lipid control.

1. Identify FH early – cascade screening of relatives when a case is diagnosed.
2. Initiate lipid‑lowering therapy in childhood for homozygous FH, and in adolescence for heterozygous FH, per American Heart Association guidelines.<sup>[5]</sup>
3. Maintain LDL‑C < 100 mg/dL (2.6 mmol/L) for heterozygous FH and < 70 mg/dL (1.8 mmol/L) for those with existing cardiovascular disease.
4. Adopt lifelong heart‑healthy habits (diet, exercise, smoking avoidance).
5. Regular cardiovascular risk assessment – blood pressure, glucose, and imaging (e.g., coronary calcium score) as indicated.

Complications

If tendon xanthomas are left untreated, the primary concern is not the nodule itself but the associated lipid disorder.

• Premature atherosclerotic cardiovascular disease – myocardial infarction, stroke, peripheral arterial disease; FH patients can develop events < 40 years old.<sup>[6]</sup>
• Functional impairment – large Achilles lesions can limit walking or running; hand lesions may affect grip.
• Psychosocial impact – visible nodules may cause body‑image concerns or anxiety.
• Recurrence after surgical removal if LDL‑C remains uncontrolled.

When to Seek Emergency Care

---

References:
<sup>[1]</sup> Nordestgaard, B.G., et al. “Familial Hypercholesterolemia Is Underdiagnosed and Undertreated in the General Population.” J Clin Lipidol, 2020.
<sup>[2]</sup> Defesche, J. “The Dutch Lipid Clinic Network Criteria for Familial Hypercholesterolemia.” Clin Lipidol, 2018.
<sup>[3]</sup> Mayo Clinic. “Statins: How they work.” 2023.
<sup>[4]</sup> Raal, F.J., et al. “Regression of Tendon Xanthomas with PCSK9 Inhibition.” NEJM, 2021.
<sup>[5]</sup> American Heart Association. “Guidelines for the Management of Familial Hypercholesterolemia.” 2022.
<sup>[6]</sup> World Health Organization. “Cardiovascular disease and the impact of lipid disorders.” WHO Report, 2022.

```