Xanthomas & Lipoprotein Disorders

How Foam Cells Form: Molecular Causes and Pathophysiology

Xanthomas develop through a series of interactions between plasma lipoproteins and tissue macrophages:

• Lipoprotein leakage (extravasation): When blood lipoproteins (especially LDL, VLDL and chylomicrons) stay high for a long time, or when blood vessels become more permeable (in areas exposed to pressure or friction), lipoprotein particles leak out of the vessels and infiltrate the dermis or tendons.
• Lipid oxidation and modification: In the dermal interstitium, lipoproteins are oxidized (Ox-LDL) or modified by local enzymes.
• Uptake through scavenger receptors: Local macrophages recognize Ox-LDL through scavenger receptors (SR-A, CD36). Unlike the standard LDL receptor, scavenger receptors are not switched off by negative feedback, so macrophages keep taking up cholesterol and triglycerides without stopping.
• Foam cell formation and granulomatous reaction: Macrophages swell with lipid droplets in their cytoplasm and become foam cells, or Touton cells (multinucleated giant cells with a ring of pale cytoplasm). As foam cells pile up, they form the characteristic yellow-gray papules, nodules or plaques in the skin.

Clinical Types of Xanthoma and Their Lipoprotein Links

Xanthomas are divided into main types by lesion shape and body site. Each type is closely linked to particular plasma lipoprotein disorders in the Fredrickson classification:

• Eyelid xanthoma (xanthelasma palpebrarum):
  • Appearance: soft, flat, well-defined yellow-orange plaques or patches, appearing symmetrically at the inner corners of the eyes or on the upper or lower lids.
  • Associations: about 50% of patients have completely normal blood lipids (local causes or aging of the basement membrane). The other 50% are linked to familial hypercholesterolemia (type IIa/IIb).
• Eruptive xanthoma:
  • Appearance: small reddish-yellow papules, 1–4 mm, that erupt suddenly in crops, usually on the buttocks, thighs, chest and flexor forearms.
  • Associations: a direct sign of very severe hypertriglyceridemia (> 1000 mg/dL or > 11.2 mmol/L), linked to types I, IV and V, with a particular risk of acute pancreatitis.
• Tuberous xanthoma:
  • Appearance: large, firm, yellow-gray nodules ranging from a few millimeters to several centimeters, on pressure points such as the elbows, knees and heels.
  • Associations: typical of familial hypercholesterolemia (type IIa) or mixed hyperlipoproteinemia (type III, remnant removal disease).
• Tendinous xanthoma:
  • Appearance: firm masses attached to tendons under the skin, most often the Achilles tendon and the finger extensor tendons.
  • Associations: a highly diagnostic clinical sign of homozygous or heterozygous familial hypercholesterolemia (type IIa).
• Planar xanthoma:
  • Appearance: flat, superficial yellow plaques in the palmar creases (palmar xanthoma, characteristic of type III) or spread widely over the neck and chest (linked to hypergammaglobulinemia or myeloma).

Diagnosis and Systemic Screening at Haute-Derma

When a patient comes in with a suspected xanthoma, we follow a structured diagnostic work-up:

• Clinical examination and dermoscopy: assessing the shape, number and density of lesions. Dermoscopy shows bright, uniform yellow areas (yellowish homogeneous areas) surrounded by a network of fine, dilated superficial vessels.
• Comprehensive lipoprotein blood tests:
  • Lipid panel: total cholesterol, triglycerides, LDL-C, HDL-C, ApoB and lipoprotein(a).
  • Blood glucose and liver/kidney function: screening for secondary causes such as type 2 diabetes, nephrotic syndrome, primary biliary cirrhosis and hypothyroidism.
• Histopathology (punch biopsy if needed): under the microscope, the epidermis is slightly thinned and the dermis is filled with foam cells, Touton giant cells and scattered lipid deposits.
• Cardiovascular screening and genetic counseling: if tendinous or tuberous xanthomas are found, the patient is referred for echocardiography and ankle-brachial index (ABI) measurement, and family members are offered counseling on testing for LDLR, APOB and PCSK9 mutations.

Treatment at Haute-Derma

Treating xanthomas requires close coordination between medical treatment of the underlying metabolic cause and cosmetic procedures to restore the skin:

Medical and Metabolic Control (The Foundation)

• Severe hypertriglyceridemia (eruptive xanthoma):
  • A fibrate (fenofibrate) combined with high-dose omega-3 (2–4 g/day).
  • Tight blood sugar control if diabetes is also present.
  • Outcome: eruptive xanthomas can clear completely within 2–3 months once triglycerides return to a safe level.
• Hypercholesterolemia (xanthelasma, tuberous and tendinous xanthomas):
  • High-intensity statins (atorvastatin, rosuvastatin), combined with ezetimibe or a PCSK9 inhibitor.
  • A diet very low in saturated fat and rich in soluble fiber.

Cosmetic Removal of Visible Lesions at Haute-Derma

For persistent lesions (especially eyelid xanthelasma that does not fade once lipids are corrected):

• UltraPulse CO2 laser / fractional Er:YAG 2940 nm:
  • How it works: vaporizes lipid-laden foam cells in the superficial dermis layer by layer, without spreading damage to the surrounding healthy tissue.
  • Advantages: short downtime and safe depth control, well suited to the thin skin around the eyes.
• Trichloroacetic acid application (TCA 50–70%): used for small, superficial xanthelasma plaques. TCA coagulates protein and fat, forming a dry crust that peels off after 7–10 days.
• Surgical excision: for large xanthelasma (> 5 mm), lesions infiltrating down to the orbicularis oculi muscle, or large tuberous xanthomas. The cosmetic suture line is hidden in the natural eyelid crease.