Like rheumatoid arthritis, fibromyalgia tends to affect women more often than men. All told, according to the American College of Rheumatology, fibromyalgia affects 3 to 6 million Americans. It primarily occurs in women of childbearing age; however, children, the elderly and men can also be affected.

This is a soft tissue rheumatism, in which there is a great deal of pain in the muscles and bone attachments. The Arthritis Foundation says this condition is referred to as a "syndrome" - because it's a set of signs and symptoms that occur together. The most prominent symptom is pain and tenderness, particularly in the neck, shoulders and hips.

In addition to pain and tenderness, fibromyalgia can also cause

• fatigue
• sleep disturbances
• numbness and tingling
• mood changes

Because the symptoms of fibromyalgia vary from person to person, and because they resemble other conditions, this can be a very difficult disease to diagnose.