Xanthoma Analysis – Diagnosing Fatty Deposits

What is Xanthoma Analysis?

Xanthoma analysis refers to the systematic clinical and laboratory-based evaluation of xanthomas. Xanthomas are yellowish-orange deposits of lipids (fats) that accumulate in the skin, tendons, or other tissues. They form when certain immune cells called macrophages absorb excess fatty substances and cluster within tissue. Analyzing these deposits provides important clues about underlying lipid metabolism disorders (dyslipidemias) and associated medical conditions.

Types of Xanthomas

As part of xanthoma analysis, different types of xanthomas are distinguished, as their shape and location can point to specific metabolic disorders:

• Tendinous xanthomas: Deposits in tendons, commonly the Achilles tendon or extensor tendons of the fingers. Typical of familial hypercholesterolemia.
• Tuberous xanthomas: Nodular deposits over joints such as the elbows or knees. Indicative of severe hyperlipidemia.
• Plane xanthomas: Flat, yellowish skin discolorations, often found in skin folds.
• Xanthelasmas: Yellow plaques on the eyelids. Frequently associated with elevated LDL cholesterol levels.
• Eruptive xanthomas: Sudden-onset small papules, typically seen with markedly elevated triglyceride levels.

Causes and Underlying Conditions

Xanthomas most commonly arise in association with lipid metabolism disorders. Xanthoma analysis helps identify the following conditions:

• Familial hypercholesterolemia: A genetic disorder characterized by significantly elevated LDL cholesterol levels.
• Hypertriglyceridemia: Elevated triglyceride levels in the blood.
• Combined hyperlipoproteinemia: Simultaneously elevated cholesterol and triglyceride levels.
• Secondary dyslipidemias: Lipid disorders resulting from other conditions such as diabetes mellitus, hypothyroidism, or kidney failure.
• Rare storage diseases: For example, Niemann-Pick disease or cerebrotendinous xanthomatosis (CTX).

How is Xanthoma Analysis Performed?

Clinical Examination

The first step in xanthoma analysis is a thorough clinical inspection of the skin, tendons, and mucous membranes by a physician. The type, size, color, and location of the deposits are documented and assessed.

Laboratory Testing

In addition to the clinical examination, blood tests are carried out to determine the lipid profile. The following values are measured:

• Total cholesterol
• LDL cholesterol (low-density lipoprotein)
• HDL cholesterol (high-density lipoprotein)
• Triglycerides
• Apolipoproteins (e.g., ApoB, ApoA1)

Histological Examination

In unclear cases, a tissue biopsy of the xanthoma may be taken and examined under a microscope. The hallmark finding is the presence of foam cells – lipid-laden macrophages that produce the characteristic histological pattern of a xanthoma.

Genetic Testing

When a hereditary lipid disorder is suspected, molecular genetic testing may be recommended to detect mutations in genes such as LDLR, APOB, or PCSK9.

Clinical Significance

Xanthoma analysis is clinically important because xanthomas are often considered an external sign of an increased cardiovascular risk. Markedly elevated blood lipid levels promote the development of atherosclerosis and can lead to heart attack or stroke over time. Early detection and treatment of the underlying lipid disorder is therefore crucial.

Treatment

Treatment is directed at the underlying cause of xanthoma formation. Possible therapeutic approaches include:

• Dietary modification: Reduction of saturated fatty acids and simple carbohydrates.
• Lipid-lowering medication: Use of statins, fibrates, PCSK9 inhibitors, or other lipid-lowering drugs.
• Treatment of the underlying condition: In secondary dyslipidemias, treating the causative disease is the primary focus.
• Surgical or cosmetic removal: Xanthomas can in certain cases be removed surgically, by laser, or via cryotherapy; however, without addressing the root cause, they often recur.

References

1. Fredrickson DS, Lees RS. - A system for phenotyping hyperlipoproteinemia. Circulation, 1965.
2. Zak A et al. - Xanthomas: Clinical and laboratory findings. Prague Medical Report, 2014.
3. World Health Organization (WHO) - Cardiovascular diseases: Prevention and control. WHO Guidelines, 2021.