My sister-in-law says she has fibromyalgia and now she's saying that her daughter - who is only 14, by the way - has it too. I'm skeptical about the disease but even if it does exist, how can her daughter have it too?

Fibromyalgia is an autoimmune disease, which means that for some unknown reason, cells in the body are attacking each other. Signs and symptoms of fibromyalgia include generalized pain, joint pain, fatigue, and other problems. There is no definite way to diagnose fibromyalgia, so it's diagnosed by exclusion, which means that doctors rule out everything else before diagnosing it.

There is also a syndrome called Juvenile Fibromyalgia Syndrome, which is very similar to fibromyalgia in adults, but it affect children, most often in their early teen years. Unfortunately, also like the adult version, doctors don't know much about it. So, it is quite possible that both your sister-in-law and niece have fibromyalgia.