The facts that the pain observed in patients with CRPS can result from multiple mechanisms and that patients with CRPS do not respond equally to the same medications may be due in

part to its evolution in time, but it also suggests that CRPS may result from multiple aetiologies. The results of this study demonstrating that a subset of CRPS patients show elevated numbers of the CD14+CD16+ monocyte subgroup may aid in elucidating some of the different mechanisms involved in its pathophysiology. A better understanding of these mechanisms may lead to novel treatments for this very severe, life-altering condition. This study has demonstrated an increase in the percentage of the CD14+CD16+ monocyte subgroup in individuals afflicted

with CRPS. In addition, other investigators have reported mast cell involvement [47], Y-27632 concentration leucocyte accumulation in the affected Crizotinib price extremity [48] and impaired neutrophil function [49] in patients with CRPS. Thus, further evaluation of the role the immune system plays in the pathogenesis of CRPS is warranted, and may aid in elucidating disease mechanisms as well as the development of novel therapies for its treatment. We wish to graciously thank Eric B. Wong MS and Jeffrey J. Gerbino for their technical assistance. This study was supported by grants from the Commonwealth of Pennsylvania Department of Health, Drexel University College of Medicine Pain Initiative and gifts from the Tilly Family Foundation and the Sunstein family. The authors certify that they have no commercial associations that might pose a conflict of interest in connection with this article. All funding sources for this study are listed in the Acknowledgements section. PatID Gender/ Age Initiating Event/Duration Signs/Symptoms/Overall

Amino acid Pain Score NRS(0-10) Pain Medications Other Conditions CRPS01 F/68 Kyphoscoliosis; disc disease at L5-S1/22 years L5-S1 sensory loss; spontaneous burning pain in both legs; weakness; inability to move toes; severe dystrophic changes. Pain (NRS) 8 NSAIDs; anti-epileptic drugs (AED), antidepressants; intermittent narcotics; spasmolytics. L4-L5 bilateral radiculopathy; arthrosclerosis; GERD; osteoporosis; osteoarthritis; IBS; headaches CRPS02 F/44 Fall; brachial plexus traction injury (BPTI)/4·5 years Paresthesias; deep ache; deep muscle joint pain; dynamic and static allodynia; generalized from BPTI; weakness; poor initiation of movement. Pain (NRS) 8 Intravenous ketamine; intravenous lidocaine; narcotics; AED; antidepressants, lenalidomide. C5-C6 disk herniation; L4-L5-S1 radiculopathy; mitral valve prolapse; Asthma; headaches. CRPS03 F/46 Fall; repetitive strain of right brachial plexus/9 years Dynamic and static mechano allodynia; cold allodynia right upper quadrant; autonomic dysregulation; neurogenic oedema; dystonia of trunk; weakness.