Xanthoma is a skin condition caused when fat deposits form beneath the skin. The accumulation of lipids below the skin can occur for several reasons, which I will explain later. Typically xanthomas appear as sores or bumps under the skin, which are typically flat, malleable, and yellow in color.
The fat cells that appear underneath the skin can increase to over three inches in diameter (1). Xanthomas may appear on any portion of the body, but are more prevalent on the elbows, joints, tendons, feet and hands. While not dangerous, Xanthomas can cause skin disfiguration and is aesthetically unpleasing.
Adipose tissue (body fat), as well as other peripheral tissue, uses an enzyme lipoprotein lipase to cleave very-low-density lipoproteins and converting it to useable lipoproteins for the liver (2). While the entire mechanism is not important, a deficiency in lipoprotein lipase in peripheral tissue is (2). Familial lipoprotein lipase deficiency (lacking LPL), can result in type I hyperlipidemia and elevation of plasma triglyceride levels (2). Since the body is no longer converting these lipoproteins for use in the body, the, triglycerides can begin to build in the peripheral tissue. The result of elevated triglyceride levels can result in eruptive xanthomas.
Individuals with familial LDL receptor deficiency and familial defective apoprotein B-100 may accumulate low-density lipids in peripheral tissue, leading to type IIa pattern hyperlipidemia (2). The increase of plasma cholesterol levels can result in tendinous or tuberous xanthomas (2). The cause of xanthomas generally result from a faulty enzyme or faulty pathway which allow lipids to build within the body.
Xanthomas, as mentioned before, are not dangerous skin conditions. They are aesthetically displeasing; however, they may indicate another, potentially dangerous condition, such as atherosclerosis or pancreatitis (2). There are several different types of xanthomas, but for the remainder of this article, we will look at those caused by hyperlipidemia.