In the beta browser version of ICD11, fibromyalgia is listed as a chronic primary pain syndrome (Treede et al. 2015). It is categorized as chronic widespread pain, and is distinguished from other chronic widespread pain by a) tender point counts (American College of Rheumatology 1990 criteria), or b) psychosocial distress (ACR 2010). Both ACR definitions are problematic for research purposes: mechanisms of tender points are poorly understood, and using distress as inclusion criterion may lead to circular arguments.
Chronic primary pain is characterized by significant emotional distress and functional disability. It is multifactorial: biological, psychological and social factors contribute to the pain syndrome. The diagnosis is appropriate independently of identified biological or psychological contributors unless another diagnosis would better account for the presenting symptoms. Chronic Primary Pain can occur in any body site (face, low back, neck, upper limb, thorax, abdominal, pelvis, urogenital region), or in a combination of body sites (Widespread pain). In general, multiple sites of pain are associated with higher distress and disability than single sites. Chronic Primary Pain is also often associated with sleep disturbance, adverse side effects of treatments (such as medication dependence), and comorbidities (such as depression, anxiety, anger, guilt, fear, and a range of chronic medical conditions).
As part of the research consortium LOGIN we have compared the pathophysiology of fibromyalgia, other chronic widespread pain and chronic localized pain in the lower back. In those datasets, fibromyalgia patients showed higher comorbidity of anxiety and depression and more functional impairment than the other groups (Gerhardt et al. 2016). A deficit in conditioned pain modulation (CPM) was related to the spatial spread of ongoing pain, consistent with the neurobiology of endogenous pain control systems. FMS differed from CWP with respect to psychosocial burden, consistent with the shift in clinical diagnostic criteria. Tender point counts (an evoked pain measure) were still useful to identify the FMS patients (Gerhardt et al. 2017). A study using the childhood trauma questionnaire suggests that early stress exposure is associated nonspecifically with lowered pressure pain thresholds which may be related to tender points (Tesarz et al. 2016).
Experimental sleep deprivation in healthy subjects or rodents leads to symptom profiles reminiscent of fibromyalgia (e.g. widespread hyperalgesia, anxiety), suggesting a potential vicious circle of pain, hyperalgesia and sleep disturbance in fibromyalgia.
In summary, fibromyalgia is a chronic primary pain syndrome characterized by widespread pain and major comorbidities. A combination of predisposition plus an initiating painful event seem to play a role in its genesis; according to the dual hit hypothesis, traumatic events during childhood may contribute to the predisposition.
Supported by the German Federal Ministry of Education and Research (BMBF; LOGIN consortium, FKZ: 01EC1010A and 01EC1010B) and the German Research Foundation (DFG: SFB 1158 Subproject S01).
Gerhardt A, et al. (2016) Clin J Pain 32: 568–579.
Gerhardt A, et al. (2017) Pain: in press.
Schuh-Hofer S, et al. (2013) Pain 154: 1613–1621.
Tesarz J, et al. (2016) Pain 157: 1799–1809.
Treede RD, et al. (2015) Pain 156: 1003–1007.
Disclosure of Interest None declared