Primary fibromyalgia : gradual appearance of symptoms, going back as far as early childhood.
Secondary fibromyalgia : a series of aches and pain that are triggered by a particular event.
Here is a graph that show the progression of the disease in 1298 people with fibromyalgia. They were monitored over a 16 year period.1
We can see that the intensity of the symptoms varies over time. Often a person may have periods where the symptoms diminish significantly followed by a period where they increase. Furthermore, this graph allows us to conclude that fibromyalgia is a disease that evolves over time and has a slow rate of progression. On average, the intensity of the symptoms doubled over a 16-year period.
1 F.Wolfe, D.j. Hawley, 1998