Patients with lupus, an inflammatory disease in which the body's immune system attacks its own tissues, are on average seven to nine times more likely to develop heart disease than the general population. Younger women with lupus are 50 times as likely to develop the disease as young women without the disease.

The endothelium -- the single layer of cells lining blood vessel walls -- is thought to protect against heart disease. It does so in part by producing nitric oxide.