Fibromyalgia: A disease characterized by chronic pain, stiffness, and tenderness of muscles, tendons, and joints, without detectable inflammation. Fibromyalgia does not cause body damage or deformity. However, undue fatigue plagues 90 percent of patients with fibromyalgia. Sleep disorder is also common in patients with fibromyalgia. People with Fibromyalgia can experience secondary depression, and it is not uncommon for people with fibromyalgia to experience other Central Sensitivity Syndromes like irritable bowel syndrome, irritable bladder syndrome and headaches.