What is Raynaud’s disease?

A. Raynaud’s phenomenon is a condition in which certain parts of the body such as the fingers, toes, ears, and tips of the nose and ears become very cold and even numb in cold temperatures, or when you’re under stress. Normally, the body responds to heat and cold by regulating blood circulation to the skin: When hot, your cheeks might flush because of blood rushing into blood vessels in your face. When cold, these vessels constrict, moving blood flow to the body’s core. Frederick Wigley, a rheumatologist who directs the Johns Hopkins Scleroderma Center, explains that in people with Raynaud’s, this response to cold temperatures is exaggerated, and the blood flow to the body’s extremities drops dramatically. Stressful situations, which trigger the same bodily responses, can also spur an attack.

Wigley says that while about 30 percent of people would characterize themselves as cold-handed, only a small percentage experience true Raynaud’s, which includes marked color changes in the affected skin. People with Raynaud’s have attacks in which skin becomes very pale, and can sometimes turn blue. The changes usually appear in a clearly delineated area, from the fingertips to the knuckles, for instance.

Physicians distinguish between Raynaud’s disease, or primary Raynaud’s - which usually appears in adolescence or teenage years in otherwise healthy people - and secondary Raynaud’s, which is caused by another disease. Wigley explains that many rheumatic diseases can lead to secondary Raynaud’s, including rheumatoid arthritis, scleroderma, and lupus.

Primary Raynaud’s often runs in families, and while it can be annoying, it isn’t usually debilitating and doesn’t cause pain. Wigley says that once people recognize the triggers of their symptoms, they can take preventive steps to avoid attacks. “Primary Raynaud’s is not dangerous,’’ Wigley says.

Send health questions to globeanswers@gmail.com.