Primary fibromyalgia. A clinical and laboratory study of 55 patients.

The clinical symptoms of 55 patients with primary fibromyalgia (PF) were studied and compared with 30 patients with rheumatoid arthritis (RA). The PF patients expressed a more intense feeling of illness than did the RA patients. Stiffness occurred just as often in PF as in RA. Trigger points occurred less frequently in RA patients. Muscular fatigue appeared to be one of the most disabling symptoms in PF. Neurophysiological studies indicated that the fatigue was at least partly of central origin. Ischemic forearm exercise test gave no evidence of impaired glycogenolysis. Laboratory investigation revealed normal 25-hydroxyvitamin D, cobalamin, folate, estrogen, testosterone, and myoglobin in the PF patients.