Sifting the wheat from the chaff? Evidence for the existence of an asymmetric fibromyalgia phenotype.

Background: The different phenotypic presentations of fibromyalgia (FM) have been infrequently studied and may have diagnostic and therapeutic implications. The aim of this study was to explore differences between FM patients with classical symmetric (s-FM) presentation and FM patients with marked asymmetric (a-FM) pain.

Methods: We performed two consecutive cross-sectional studies on FM patients and matched healthy volunteers (HV).