See below. I have seen people with liver problems (hepatitis) have fibromyalgia. Persons with infections like lyme disease may sometimes have fibromyalgia symptoms. People with depression often have fibromyalgia. It is known that persons (usually women) with a history of physical or sexual abuse either as children or adults have a higher propensity to fibromyalgia.
Several. Cause of fibromyalgia only speculation, theories, & conjecture. My clinical data points to multivariate cause: femaleness, multiple childbirths, muscle deconditioning, low back biomechanical injury, obesity, depression, fatigue, & Joint Hypermobility Syndrome. Not to say all these apply to each case. Cause differs between individuals; knowing the person is more important than knowing the disease.
None. Fibromyalgia is not caused by another medical condition.