Platelet MAO in patients with idiopathic pain disorders.

Patients with idiopathic pain syndromes have been compared to healthy volunteers and patients with neurogenic pain syndromes as concerns the activity of the enzyme monoamine oxidase (MAO) in thrombocytes. In both patients with idiopathic pain syndromes and in patients with neurogenic pain syndromes an increased frequency of patients with low platelet MAO activity was found. As low platelet MAO activity has been suggested to reflect low central serotoninergic activity the results are in line with findings of reduced concentrations of the serotonin metabolite 5-HIAA in CSF in patients with idiopathic pain syndromes. The results would also give some support for the suggestion that idiopathic pain syndromes might be a variant of depressive disease.