According to the ACR criteria, FMS is present when a patient suffers widespread pain for at least three months and feels pain in 11 or more of the 18 pressure point sites. In the dolorimetry method, the examiner presses a rubber endplate, attached to a spring-loaded force gauge, into the tender point site with increasing force. Patients are then asked to say when they stop feeling pressure and start feeling pain. 12 FMS and Other Disorders Patients with FMS often suffer from associated diseases. The most common of these are listed in Table 3.
Some diseases also mimic FMS and cause confusingly similar complaints.
Also complicating the FMS picture is the fact that FMS sufferers often have a variety of overlapping conditions or syndromes. The most common of these are shown in Table 5. As with other diseases whose causes are not understood, some have suggested that FMS may be a psychosomatic illness or even a psychiatric disorder. In the past, FMS patients have been diagnosed as hysterical. Their chief symptom, pain, is quite subjective and is difficult to document.