Clinical expression profiles of Complex Regional Pain Syndrome, Fibromyalgia and a-specific Repetitive Strain Injury: More common denominators than pain?

Purpose. To systematically evaluate and compare the clinical manifestations, disease course, risk factors and demographic characteristics of Complex Regional Pain Syndrome type 1 ( CRPS), fibromyalgia ( FM) and a-specific Repetitive Strain Injury (RSI). Method. A literature search was performed using terms related to the aforementioned topics and diseases. Only original clinical studies that included at least 20 subjects were eligible. Results. Fifty-nine studies on CRPS, 73 on FM and 7 on a-specific RSI were identified. The diseases show similarities in age distribution, male-female ratio, pain characteristics and sensory signs and symptoms. Motor, autonomic and trophic changes are frequently reported in CRPS, but only occasionally in FM and RSI. Systemic symptoms are found in patients with CRPS and FM, and in a subgroup of patients with RSI. In all three disorders, symptoms usually start locally, but may spread to other body regions later, which, in the case of FM, is a prerequisite for diagnosis. Disease onset is always, usually, or occasionally of traumatic origin in RSI, CRPS and FM, respectively. Anxiety and depression are more frequent in patients compared to controls, but probably not very different from patients with other pain conditions or chronic diseases. Conclusions. Apart from some obvious differences between CRPS, FM and RSI, the similarities are conspicuous. The common features of CRPS, FM and a-specific RSI may suggest that a common pathway is involved, but until patients with these type of symptoms are assessed with a uniform assessment procedure, a thorough comparison cannot be made. A systematic evaluation of patients with a suspected diagnosis of CRPS, FM or RSI, may lead to a better appreciation of the differences and similarities in these diseases and help to unravel the underlying mechanisms.