SERUM SEROTONIN CONCENTRATIONS IN PATIENT S WITH GENERALIZED TENDOMYOPATHY (FIBROMYALGIA) AND RHEUMATOID-ARTHRITIS

The serum concentration of serotonin (S-5-HT) was measured in 31 patie nts with primary fibromyalgia, 21 patients with rheumatoid arthritis ( RA) (15 of them with secondary fibromyalgia) and 20 healthy volunteers . Both patients with primary fibromyalgia and rheumatoid arthritis had significantly lower S-5-HT levels when compared to healthy controls, and S-5-HT concentrations in patients with secondary fibromyalgia were even significantly lower than those of RA-patients. Unlike the patien ts with rheumatoid arthritis, a significant correlation between S-5-HT level and the number of ''tender points'' as well as mean pressure te nderness at 24 different points was found in patients with primary fib romyalgia. Conversely, in patients with rheumatoid arthritis the S-5-H T level correlated significantly with erythrocyte sedimentation rate. These results suggest different pathological mechanisms of S-5-HT decr ease in patients with primary fibromyalgia and rheumatoid arthritis. O n die other hand, they raise the question whether secondary fibromyalg ia may be a pathogenetically different syndrom mimicking symptomatical ly primary fibromyalgia.