Comment on: Increased plasma endothelin-1 levels in fibromyalgia syndrome. [Rheumatology (Oxford). 2003]
SIR, We read with interest the report by Pache et al. [1] showing increased endothelin-1 (ET-1) levels in patients with a diagnosis of fibromyalgia syndrome (FMS) and their conclusion that elevated ET-1 levels might contribute to some of the apparent vascular disturbances that characterize the syndrome. Pache et al. also point to the overlap between the clinical presentation of FMS and other ‘stress-associated disorders including chronic fatigue syndrome (CFS) and depression’. Whether FMS or CFS is stress-induced is a contentious issue in itself, but of equal concern is the view that FMS should be considered to be part of the spectrum of illness under the generic name ‘chronic fatigue syndrome’. Clearly, the symptoms of FMS and CFS have much in common [2, 3] but it has been said that FMS represents an additional burden of suffering among those with CFS [4], those patients meeting the case definitions for both FMS and CFS having a worse course, worse overall health and greater disease impact [2]. Furthermore, while many FMS patients experience fatigue, it has been estimated that only about one-fifth fulfil the specific criteria required for CFS [5]. Clinical similarities apart, there are biological differences between the two; for example, cerebrospinal fluid levels of substance P are elevated in FMS but not in CFS patients [6], and cardiovascular responses to postural challenge are characteristic of many CFS patients but are not apparent in those with FMS [7].
You can read the rest of this comment here: http://rheumatology.oxfordjournals.org/content/43/2/252.long
Source: Kennedy G, Spence V, Khan F, Belch JJ. Plasma endothelin-1 levels in chronic fatigue syndrome. Rheumatology (Oxford). 2004 Feb;43(2):252-3; author reply 253-4. http://rheumatology.oxfordjournals.org/content/43/2/252.long (Full article)