We’ve had the first taste of warm weather and many will have been applying creams to encourage brown legs. In this blog, however, I’m not writing about a sun tan. Some patients with severe obesity will develop a brown discolouration in the skin over the lower parts of the legs.
To understand why this happens, it’s important to know something about blood flow. When the heart pumps oxygen-rich blood to the tissues, the blood is carried in arteries. The tissues remove the oxygen and the blood is returned to the heart and lungs via the veins. In the legs, the large veins pass through the groin area which is where problems can arise. People with large amounts of “central” fat – fat around the waist area – the veins may be compressed leading to blood and fluid collecting in the lower legs. This presents as swelling initially, but can also lead to redness of the skin (“stasis dermatitis”) and eventually brown staining. The brown discolouration actually comes from iron in the blood which moves into the skin tissues. In severe and chronic cases, the skin can break down leading to ulceration and infection.
Experience suggests that when patients lose weight, the skin staining improves, but it never disappears entirely (some patients are very good at disguising the brown colour with artificial sun tan). However the swelling of the legs almost invariably improves and in many cases will disappear entirely - another good reason for losing weight.
Dr David Ashton
12th April 2011