Author: Vanessa Ngan, Staff Writer; Dr Amy Stanway, Dermatology Registrar, Nottingham, United Kingdom, 2005.
A xanthoma is a skin lesion caused by the accumulation of fat in macrophage immune cells in the skin and more rarely in the layer of fat under the skin.
Some types of xanthoma are indicative of lipid metabolism disorders (e.g. hyperlipidaemia or high blood fats), where they may be associated with increased risk of coronary artery heart disease and occasionally with pancreatitis.
Xanthomas are classified into the following types based on where they are found on the body and how they develop.
Diffuse plane xanthomatosis
There are several underlying disorders in which xanthoma is caused by a disturbance in lipid (fat) metabolism. Because lipids are insoluble in water they combine with proteins to form compounds called lipoproteins. Lipoproteins transport lipids and cholesterol in the blood to different parts of the body. Depending on their size and weight, the common lipoproteins are classified as chylomicrons, very-low-density lipoproteins (VLDL), low-density-lipoproteins (LDL), and high-density-lipoproteins (HDL) (Fredrickson classification). They all have a role to play in maintaining metabolic functioning of the body.
Alterations in lipoproteins may be a result of a genetic defect (e.g. primary hyperlipoprotenaemia) or from some underlying systemic disorder such as diabetes mellitus, hypothyroidism, or nephrotic syndrome. These underlying diseases can cause elevated levels of certain lipids and lipoproteins, which then manifest as cutaneous xanthoma.
Monogenic familial hypercholesterolaemia: Type IIa
Polygenic familial hypercholesterolaemia: Type IIa
Polygenic familial combined hyperlipidaemia: Type IIb
Severe hypertriglyceridaemia: Type 1 and V
Broad beta hyperliproteinaemia: Type III
The reason for the appearance of xanthoma when the blood fats are normal is not understood at this time.
A skin biopsy may be necessary to confirm a clinical diagnosis of xanthoma. See eruptive xanthoma pathology.
Appropriate blood and urine tests and X-rays are performed to determine the cause of disturbed lipoprotein levels if they are present. The risk of cardiovascular disease, including heart attacks, peripheral vascular disease and stroke, is increased with elevated levels of certain lipoproteins. It is essential to identify the contributing factors so that appropriate therapy can be established.
The main aim of treatment for xanthoma that is associated with an underlying lipid disorder is to identify and treat the lipid disorder. In many cases, treating the underlying disorder will reduce or resolve the xanthoma. In addition, treating hyperlipidaemia will reduce the risk of heart disease, and treating hypertriglyceridaemia will prevent pancreatitis. Dietary and lifestyle modifications with or without medication are used to treat lipid disorders.
Dietary measures should include:
Very effective medications may also be prescribed. These may include:
Surgery or locally destructive modalities can be used to remove xanthomas that do not resolve spontaneously or with treatment of the underlying cause. Xanthoma disseminatum affecting vital organ functions may be treated by chemotherapy drugs or radiotherapy.
Treatments for xanthelasma include:
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