The association of functional gastrointestinal disorders and fibromyalgia

Previous epidemiological studies have confirmed the clinical impression that functional gastrointestinal disorders typically overlap with fibromyalgia (FM) in the same patient, suggesting a common etiology. FM syndrome occurs in up to 60% of patients with functional bowel disorders. Up to 50% of patients with a diagnosis of FM syndrome complain of symptoms characteristic of functional dyspepsia and 70% have symptoms of IBS. These two conditions have common clinical characteristics: (1) the majority of patients associate stressful life events with the initiation or exacerbation of symptoms, (2) the majority of patients complain of disturbed sleep and fatigue, (3) psychotherapy and behavioral therapies are efficacious in treating symptoms, and (4) low-dose tricyclic antidepressant medication can improve symptoms. Despite these similarities, their perceptual responses to both somatic and visceral stimuli differ. While FM patients characteristically exhibit somatic hyperalgesia, IBS patients without coexistent FM have somatic hypoalgesia to mechanical stimuli. Visceral distention studies have also demonstrated perceptual alterations in patients with IBS and FM although these findings appear to differ in the two conditions. Further studies will help explore the mechanisms which are responsible for the similarities and differences in clinical symptoms and physiologic parameters seen in IBS and FM.