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.

Xanthelasma palpebrum – Lesions arise symmetrically on upper and lower eyelids.

Tuberous xanthomas – Firm, painless, red-yellow nodules that develop around the pressure areas such as the knees, elbows, heels and buttocks.

Tendinous xanthoma – Appears as slowly enlarging subcutaneous nodules related to a tendon or ligament. Most commonly found on the hands, feet, and Achilles tendon.

Eruptive xanthomas – Most commonly arise over the buttocks, shoulders, arms and legs but may occur all over the body.

Plane xanthoma – Lesions are flat papules or patches that can occur anywhere on the body.

Diffuse plane xanthomatosis – Presents with large flat reddish-yellow plaques over the face, neck, chest, buttocks and in skin folds (such as the armpits and groin).

Xanthoma disseminatum – The skin lesions usually consist of hundreds of small yellowish-brown or reddish-brown bumps, which are usually evenly spread on both sides of the face and trunk. They may particularly affect the armpits and groins.

There are several underlying disorders in which xanthoma is caused by a disturbance in lipid (fat) metabolism.