According to the Gale Encyclopedia of Senior Health, fibromyalgia (which is also known as fibromyositis or fibromyalgia syndrome) is "an inflammation of the fibrous or connective tissue (muscles, joints, ligaments, and tendons) of the body" (2nd edition, 2015). Formerly known as fibrositis, this chronic disorder does not have an identifiable cause, but is characterized by symptoms such as widespread muscle pain, fatigue, and specific areas of soreness on the body. More specific symptoms include the following:

• Pain and stiffness all over the body
• Fatigue and tiredness
• Problems with thinking, memory, and concentration
• Depression and anxiety
• Headaches, including migraines
• Irritable bowel syndrome
• Numbness or tingling in the hands and feet
• Pain in the face or jaw 
• Sleep problems

Symptom information from Medline Plus, Fibromyalgia

• Most people who develop fibromyalgia are middle-aged adults
• Can affect any age group, but is most common in women between the ages of 20 and 50
• Between 3 and 6 million people in the United States have fibromyalgia (1 person in every 50)
• The female/male ratio of those diagnosed is 7:1 
• Between 25%-65% of those diagnosed have another concurrent rheumatic condition, such as rheumatoid arthritis

Statistics from Gale Encyclopedia of Senior Health

Due to the uncertainty of what causes fibromyalgia and the resulting difficulty in diagnosis, this condition is sometimes considered controversial in the medical community. As a result, those affected by this syndrome can be subjected to skepticism regarding the extent of their pain and suffering. According to an article published in Scope, a blog founded and produced by the Stanford University School of Medicine, a patient with fibromyalgia described living with a "nonexistent illness." They noted withdrawing themselves in many aspects of life in order to "minimize [their] chances of being criticized or attacked by those who don't understand." It was only when they were given a diagnosis that they felt validated to say what they were feeling was "real."

Article from Scope, Fibromyalgia - living with a controversial chronic disease