One way in which FM is different from CFS is that pain is the main symptom with the former, while fatigue is the main symptom in the latter.
Pain as experienced by fibromyalgia patients is both widespread and severe, and is often accompanied by stiffness. When doctors examine fibromyalgia patients, they find several spots that are tender to touch. Detecting these spots, known as tender points, helps diagnose fibromyalgia. This brings us to a point of difference between the two conditions as CFS patients do not complain of tender points that FM patients do.
CFS, on the other hand, has one core symptom which is fatigue. It can be totally incapacitating. Usually, fatigue in CFS patients that has been pre-existing for over six months is generally accompanied by:
Tender or enlarged lymph nodes