Genetic HLA Associations in Complex Regional Pain Syndrome With and Without Dystonia

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1 The Journal of Pain, Vol 13, No 8 (August), 2012: pp Available online at and Genetic HLA Associations in Complex Regional Pain Syndrome With and Without Dystonia Diana E. van Rooijen,* Dave L. Roelen, y Willem Verduijn, y Geert W. Haasnoot, y Frank J. P. M. Huygen, x Roberto S. G. M. Perez, { Frans H. J. Claas, y Johan Marinus,* Jacobus J. van Hilten,* and Arn M. J. M. van den Maagdenberg*,z Departments of *Neurology, y Immunohaematology and Blood Transfusion, and z Human Genetics, Leiden University Medical Center, Leiden, The Netherlands. x Department of Anesthesiology, Erasmus Medical Center, Rotterdam, The Netherlands. { Department of Anesthesiology, VU University Medical Center, Amsterdam, The Netherlands. Abstract: We previously showed evidence for a genetic association of the human leukocyte antigen (HLA) system and complex regional pain syndrome (CRPS) with dystonia. Involvement of the HLA system suggests that CRPS has a genetic component with perturbed regulation of inflammation and neuroplasticity as possible disease mechanisms. However, it is at present unclear whether the observed association with HLA-B62 and HLA-DQ8 in CRPS patients with dystonia also holds true for patients without dystonia. Therefore, we tested the possible association with HLA-B62 and HLA-DQ8 in a clinically homogeneous group of 131 CRPS patients without dystonia. In addition, we investigated the possible association with other alleles of the HLA-A, HLA-B, HLA-C, HLA-DR, and HLA-DQ loci. We showed an increased prevalence of HLA-DQ8 (molecularly typed as HLA-DQB1*03:02; OR = 1.65 [95% CI ], P =.014) in CRPS without dystonia, whereas no association was observed for HLA-B62 (molecularly typed as HLA-B*15:01; OR = 1.22 [95% CI ], P =.458). Our data suggest that CRPS with and CRPS without dystonia may be genetically different, but overlapping, disease entities because only HLA-DQ8 is associated with both. The findings also indicate that distinct biological pathways may play a role in both CRPS subtypes. Perspective: This study is the first to replicate a specific HLA region conferring genetic risk for the development of CRPS. Moreover, associations of HLA-DQ8 with both CRPS with and CRPS without dystonia, and HLA-B62 only with CRPS with dystonia, suggest that these disease entities may be genetically different, but overlapping. ª 2012 by the American Pain Society Key words: Complex regional pain syndrome, genetics, human leukocyte antigen, major histocompatibility complex, dystonia. Received February 21, 2012; Revised March 29, 2012; Accepted May 17, This study is part of TREND (Trauma RElated Neuronal Dysfunction), a Dutch Consortium that integrates research on epidemiology, assessment technology, pharmacotherapeutics, biomarkers and genetics on Complex Regional Pain Syndrome type 1. The Consortium aims to develop concepts on disease mechanisms that occur in response to tissue injury, its assessment and treatment. TREND is supported by a government grant (BSIK03016). All authors declare that they have no conflict of interest with respect to the subject of this study. Jacobus J. van Hilten and Arn M. J. M. van den Maagdenberg are shared last authors. Address reprint requests to Arn M. J. M. van den Maagdenberg, PhD, Leiden University Medical Center, Department of Human Genetics, PO Box 9600, 2300 RC Leiden, The Netherlands. maagdenberg@lumc.nl /$36.00 ª 2012 by the American Pain Society Complex regional pain syndrome (CRPS) is a multifactorial disorder of largely unknown etiology that is associated with an aberrant host response to tissue injury of 1 or more limbs. The clinical spectrum of CRPS is heterogeneous with different combinations of sensory, autonomic, trophic, and motor changes, which can include dystonia, of the affected limb. The clinical heterogeneity seen in CRPS may be a reflection of different combinations of biological pathways presumed to be involved in CRPS that include aberrant inflammation, vasomotor dysfunction, and maladaptive neuroplasticity. 18 Tissue injury seems the key environmental factor that leads to CRPS, but immobilization of the affected limb and use of angiotensin-converting enzyme inhibitors, which enhance an inflammatory response, may contribute to the onset of CRPS. 3,18 Genetic epidemiological studies have provided evidence of genetic factors 784

2 van Rooijen et al The Journal of Pain 785 involved in the disease as CRPS may occur in familial form 4 and there seems an increased risk of disease developing in siblings of patients with young-onset CRPS. 5 Given the important role of inflammation, genetic studies in CRPS mainly focused on components of the human leukocyte antigen (HLA) system conferring susceptibility to develop CRPS. The HLA system is divided into 3 classes (Classes I III) of genes that play important roles in regulating the immune response. 15,21 Early genetic studies revealed significant associations of CRPS with HLA-DQ1 14,30 and HLA-DR6 30 and of CRPS with dystonia with HLA-DR13. 26,28 However, the observed HLA associations are likely confounded by phenotypic heterogeneity, statistical analysis of unplanned post hoc analyses, and/or underpowered study designs. These limitations were addressed in our previous HLA association study in which we analyzed a large, clinically homogeneous group of 150 CRPS patients with dystonia. In this subset of CRPS patients a genetic association was observed with HLA-B62 and HLA-DQ8. 6 In the present study, we tested whether these associations are also observed in a large clinically homogeneous group of CRPS patients without dystonia. Thus, we provide evidence whether CRPS with and CRPS without dystonia should genetically be considered as different disease entities. Secondly, we screened for other associations with HLA alleles in this group of CRPS patients. Methods Recruitment of CRPS Patients Between April 2004 and March 2010, 131 Dutch Caucasian CRPS type I patients were recruited at the Departments of 1) Neurology of the Leiden University Medical Center; 2) Anesthesiology of the VU University Medical Center; and 3) Anesthesiology of the Erasmus Medical Center. Patient recruitment was performed within the national Trauma-RElated Neuronal Dysfunction (TREND) consortium ( which integrates Dutch research on CRPS. CRPS was diagnosed by specialists of the participating centers, who are experienced in diagnosing and treating CRPS patients and in using appropriate tests to exclude other causes of CRPS. Patients were excluded if additional tests revealed a different clinical diagnosis. In TREND, the acquisition of data concerning the clinical diagnosis and other phenotype characteristics is performed in a standardized manner, after which this information is stored in a central internet-based database. This strategy was chosen to obtain a homogeneous group of patients with CRPS, which is very challenging, instead of maximizing the sample size by also including less well-characterized patients. Homogenization of clinical diagnoses was ensured by including only CRPS patients who fulfilled the Budapest Research criteria 10 (Supplementary Table 1). Clinical characteristics of the patients and controls are displayed in Table 1. Informed consent was obtained from all patients, and the study protocol was approved by the local Ethics Committees of the participating centers. Table 1. Demographic Information of Participants HEALTHY CONTROLS CRPS WITHOUT DYSTONIA CRPS WITH DYSTONIA Number of 5, participants Percentage (N) of 59 (3,318) 79 (103) 88 (132) females Mean (SD) age 36.2 (8.7) 47.7 (12.6) 41.3 (12.4) Mean (SD) age at 43.2 (10.8) 31.5 (12.0) onset, years Median (IQR) disease duration, years 2.2 (.9 5.5) 8.7 (4.0 14) Abbreviations: N, number; IQR, interquartile range. HLA Genotyping HLA DNA typing was performed for HLA-A (20 alleles), HLA-B (40 alleles), and HLA-C (14 alleles) using a commercially available reverse-line hybridization strip assay (RELIÔ SSO; Invitrogen, Washington, DC). Polymerase chain reaction (PCR) amplification and hybridizations were done according to manufacturer s recommendations. HLA-DR (14 alleles) and HLA-DQ (7 alleles) were typed with a reversed approach of the PCR-sequencespecific oligonucleotide probe technique described elsewhere. 31 The interpretation of the raw data was carried out with computer-assisted analysis software. 11 Frequencies of HLA alleles in cases were compared with those of 5,604 randomly selected healthy Dutch blood donors who were previously genotyped (Table 1). Statistical Analysis This study had 2 aims. In the primary analysis, we tested whether the earlier described association between CRPS with dystonia and HLA-B62 and HLA-DQ8 alleles also exists in our CRPS sample. A multivariate logistic regression model with group (ie, patient or control) as dependent variable was used to test whether age and sex influenced the results. As a secondary, exploratory, analysis, we tested the possible association of other HLA alleles with CRPS. Genetic associations for HLA alleles were assessed by chi-square tests based on a 22 contingency table. P values were obtained with the two-sided Fisher s exact test. Only for the secondary analyses, corrected P values (P c ) were calculated to prevent type I errors due to multiple testing for multi- HLA alleles, as described before. 8,23 P c values were calculated using the following formula: P c =1 (1 p) n, where p is the obtained P value and n the estimated number of HLA alleles present within the respective locus examined (ie, 20 alleles for HLA-A, 39 for HLA-B, 14 for HLA-C, 14 for HLA-DR, and 6 for HLA-DQ). A P or a P c less than.05 was considered a significant difference. Odds ratios (OR) with 95% confidence interval (CI) were calculated according to the Woolf-Haldane test. 11 Re-analysis of HLA Associations in CRPS With Dystonia The results of our previous study of CRPS patients with dystonia were based on typing by serology and

3 786 The Journal of Pain HLA Associations in Complex Regional Pain Syndrome compared with a smaller control panel (n = 2,440). 6 Since that time, molecular HLA typing has become widely used in HLA laboratories, so to avoid methodological differences that may hamper comparisons between the 2 studies, we re-analyzed the allele frequencies of the CRPS sample with dystonia (n = 150) using the DNA control panel of 5,604 healthy Dutch blood donors. Results Primary Analysis of HLA-DQ8 and HLA- B62 in CRPS As a primary analysis we tested the frequencies of HLA alleles DQ8 (molecularly typed as HLA-DQB1*03:02) and HLA-B62 (molecularly typed as HLA-B*15:01) in our set of 131 well-characterized CRPS patients who fulfilled the Budapest Research criteria and did not exhibit dystonia against 5,604 healthy Caucasian Dutch blood donors. Initial (uncorrected) analysis of the 2 target HLA alleles revealed a significant association with HLA- DQ8 (OR = 1.65 [95% CI ], P =.014), whereas no association with HLA-B62 was found (OR = 1.22 [95% CI ], P =.458) (Table 2). Logistic regression showed that HLA-DQ8 is independently associated with CRPS after adjusting for age and sex (Supplementary Table 2). To optimally compare the results with CRPS patients who also have dystonia, we re-analyzed the association by comparing the frequencies of HLA alleles with those of the same control panel. The 2 alleles showed significant association, similar to findings in the original study, 6 with HLA-DQ8 having an OR = 1.85 (95% CI , P =.001) and HLA-B62 having an OR = 2.07 (95% CI , P <.001). Thus we provide genetic clues that CRPS without and CRPS with dystonia are genetically different, but overlapping, phenotypes. Secondary Analysis of HLA Alleles in CRPS Without Dystonia In a secondary analysis, we tested the remaining 93 HLA alleles of the HLA-A, HLA-B, HLA-C, HLA-DR, and HLA-DQ loci for association in our set of CRPS patients compared to the large cohort of Caucasian Dutch blood donor controls. The results of all tested alleles per locus are presented in Supplementary Tables 3 to 7. Table 2. Primary Analysis Odds Ratios and P Values Estimated for HLA Alleles Typed Among CRPS Cases With and Without Dystonia and Control Subjects HLA ALLELES SEROTYPE % CASES % CONTROLS OR 95% CI P CRPS without dystonia B*15:01 B DQB1*03:02 DQ CRPS with dystonia B*15:01 B <.001 DQB1*03:02 DQ In this exploratory analysis, 6 HLA alleles showed association with disease when uncorrected for multiple testing: HLA-B13 (OR = 2.24 [95% CI ], P =.024); HLA-B37 (OR = 2.32 [95% CI ], P =.041); HLA-Cw4 (OR =.58 [95% CI.36.94], P =.020); HLA-Cw6 (OR = 1.64 [95% CI ], P =.023); HLA-DR4 (OR = 1.51 [95% CI ], P =.030); HLA-DR11 (OR = 1.57 [95% CI ], P =.043) (Table 3). However, after correction for comparisons of multiple HLA alleles (P c ), according to Edwards, 8 none of the associations remained significant. Although our sample size of 131 cases is relatively small albeit almost the largest worldwide and because this size likely prohibited identifying additional significant HLA associations, we consider these findings hypothesis generating that should be analyzed in other CRPS cohorts in the future. Discussion HLA alleles HLA-DQ8 and HLA-B62 showed genetic association in our previous study of CRPS patients who also developed dystonia. 6 Here, we tested whether an association can also be found in a clinically homogeneous group of CRPS patients fulfilling the Budapest criteria but who did not suffer from dystonia. In our primary analysis, in which we tested only the HLA-DQ8 (molecularly typed as DQB1*03:02) and HLA-B62 (molecularly typed as HLA-B*15:01) alleles, an association was only found with HLA-DQ8. In our secondary, exploratory, analysis several associations were observed with other HLA alleles, but none survived multiple testing correction, likely due to the relatively small sample size in the case group. Still, we consider our findings of the secondary analysis noteworthy as future studies should investigate whether 1 or more of these associations are genuine. Regardless, this study and the study by de Rooij et al 6 showed that the HLA system seems to be involved in CRPS, which would make the 6p21 region the first robustly replicated chromosomal region conferring some genetic risk to develop CRPS. Our main genetic finding is that an association was found with HLA-DQ8 in both CRPS patients without dystonia (this study) and CRPS patients with dystonia. 6 Thus, the evidence is accumulating that HLA-DQ8 predisposes to the development of CRPS. Although this is beyond the scope of this study, one could speculate on a possible biological pathway underlying CRPS. Within the HLA system of the major histocompatibility complex (MHC) region, molecules from HLA Class I bind to peptides derived from intracellular proteins and present these to CD81 T-cells, whereas the HLA-peptide complex from Class II present extracellular peptides to CD41 T-helper cells. Class III genes regulate complement components, tumor necrosis factor alpha, and other genes. 17,21 The genotype HLA-DQ8, together with HLA-DQ2, has a strong association with, for instance, celiac disease, which in this case is characterized by an aberrant inflammatory response, in this case response of the small intestine to gluten. 22 Also, in CRPS there are initial clinical features (ie, pain, swelling, redness, warmth) that suggest that aberrant inflammation is an important

4 van Rooijen et al The Journal of Pain 787 Table 3. Secondary Analysis Odds Ratios and P Values Estimated for HLA Alleles Typed Among CRPS Cases and Control Subjects HLA ALLELES SEROTYPE %CASES %CONTROLS OR 95% CI P P C B*13 B B*37 B C*04 Cw C*06 Cw DRB1*04 DR DRB1*11 DR NOTE. The results of all tested alleles per locus are presented in Supplementary Tables 3 to 7. mechanism in CRPS. 18 In addition, several studies revealed that both nociceptive afferents and the skin s immune system contribute to aberrant inflammation as observed in CRPS. 7,12 In celiac disease the association with, for instance, HLA-DQ8 is explained by the role of HLA in binding gluten-peptides on antigen presenting cells. Gluten-specific CD41 T-cells in the lamina propria of the small intestine respond to these peptides, which in turn enhances cytotoxicity of locally present lymphocytes against the intestinal epithelium. 24 The subsequent development of the inflammatory process is also determined by a variety of factors involved in enhancing gluten peptides affinity to bind to gliadin T-cell epitopes and promoting downstream inflammatory effects. 24 The proposed mechanism of celiac disease is that once a threshold of gluten on T-cells has been reached, a self-amplifying loop mediating a continuous inflammatory response is established. 24 At present the exact nature of the inflammatory process in CRPS in relation to HLA-DQ8, as well as other inflammatory responses is unclear. Interestingly, though, studies on cytokines in artificially drawn blister fluid of the affected extremity of CRPS patients revealed that levels of interleukin-1 and tumor necrosis factor alpha remained elevated over a period of 3 years. 32 Moreover, recently autoantibodies against muscarinic-2 receptor and b 2 adrenergic receptor in CRPS were shown. 16 It would seem possible that peptides derived from these 2 receptors, towards which autoantibodies were found, could possibly be presented in HLA-DQ8. This interesting possibility should be investigated in depth by additional studies. Despite important differences between celiac disease and CRPS, shared characteristics, including a role of HLA-DQ8, inflammation, and tissue injury in both disorders, seem to suggest that complex gene-environment interactions may serve as an interesting model for future research in CRPS. 25 Given the relatively low OR observed in our studies, HLA-DQ8 plays a small role in the development of CRPS, and its presence is not required to develop the disease. This is not uncommon, because in most diseases there is a complex interplay between genetic and environmental factors. 33 Unlike with DQ8 that showed association in both CRPS with and CRPS without dystonia, we did not observe an association with HLA-B62 in patients who do not exhibit dystonia. This indicates that the 2 CRPS patient groups are genetically different. It is tempting to speculate why only in CRPS patients with dystonia is there an association with HLA-B62. One could postulate that there might be an interaction effect between Class I and Class II alleles in the development of dystonia. A combined role of HLA Class I and II in disease is uncommon but has been reported in, for example, diabetes mellitus type I. 13 Additionally, MHC Class I molecules have been implicated in nonimmunological functions such as neural development and synaptic plasticity, 1,9 and their presence was demonstrated presynaptically at the neuromuscular junction and in spinal motor neurons. Notably, MHC Class 1 deficient mice showed an altered innervation pattern of muscle fibers, with some muscle fibers having a higher density of neuromuscular junctions. 2 Axotomization of motoneurons in these mice led to synaptic reorganization that was strongly disrupted compared to wildtype mice. 19 Collectively, the limited data on MHC Class I molecules in neurons suggest that HLA Class I may play a role in biological pathways underpinning aberrant neuroplasticity, a mechanism considered to be important in the development chronic pain and dystonia in CRPS. 27,29 A limitation of our approach is that the study was not powered to directly compare the results of the genotypes between the 2 patient groups. The aim was to compare the HLA types of the patients with a control group, similar to what was done in the first study that compared CRPS patients with dystonia with controls. 6 A direct comparison of the 2 patient groups would need much larger numbers than 150 patients per group to take the various HLA alleles into account. This is due to the fact that HLA is an enormous polymorphic system, which is reflected by the more than 7,000 recognized different HLA alleles. 20 By choosing a large control panel we are (almost) sure that all HLA alleles of the CRPS patients are covered in the control population, and therefore we consider the current approach valid and efficient. Moreover, we have been able to show robust results despite the relatively small sample size of the patient groups. The comparison of HLA- B62 frequencies between the control group and CRPS patients with dystonia is very significant, whereas the comparison between controls and CRPS patients without dystonia is not. Additionally, when inspecting the prevalence of HLA-B62 in CRPS patients without dystonia, the percentage of patients with HLA-B62 is almost equal to that of the control group. Future studies combining large patient cohorts should verify whether CRPS

5 788 The Journal of Pain HLA Associations in Complex Regional Pain Syndrome patients with and without dystonia are genetically different or not. In conclusion, our data suggest that CRPS patients with and without dystonia may be genetically different and that the associations with HLA-DQ8 and HLA-B62 in CRPS with dystonia, and HLA-DQ8 only in CRPS without dystonia, could point to distinct pathophysiological mechanisms that might explain the perturbed regulation of inflammation and neuroplasticity in CRPS. Acknowledgments We thank the generous participation of CRPS patients and controls. We would like to thank Florencia Gosso for her contribution during the initial phase of the study. References 1. Corriveau RA, Huh GS, Shatz CJ: Regulation of class I MHC gene expression in the developing and mature CNS by neural activity. Neuron 21: , Cullheim S, Thams S: Classic major histocompatibility complex class I molecules: New actors at the neuromuscular junction. Neuroscientist 16: , de Mos M, Huygen FJ, Stricker BH, Dieleman JP, Sturkenboom MC: The association between ACE inhibitors and the complex regional pain syndrome: Suggestions for a neuro-inflammatory pathogenesis of CRPS. Pain 142: , de Rooij AM, de Mos M, Sturkenboom MC, Marinus J, van den Maagdenberg AM, van Hilten JJ: Familial occurrence of complex regional pain syndrome. Eur J Pain 13: , de Rooij AM, de Mos M, van Hilten JJ, Sturkenboom MC, Gosso MF, van den Maagdenberg AM, Marinus J: Increased risk of complex regional pain syndrome in siblings of patients? J Pain 10: , de Rooij AM, Florencia GM, Haasnoot GW, Marinus J, Verduijn W, Claas FH, van den Maagdenberg AM, van Hilten JJ: HLA-B62 and HLA-DQ8 are associated with Complex Regional Pain Syndrome with fixed dystonia. Pain 145:82-85, Eberle T, Doganci B, Kramer H, Fechir M, Wagner I, Sommer C, Birklein F: Mechanical but not painful electrical stimuli trigger TNF alpha release in human skin. Exp Neurol 221: , Edwards JH: HLA and disease: Detection of associations. J Immunogenet 1: , Goddard CA, Butts DA, Shatz CJ: Regulation of CNS synapses by neuronal MHC class I. Proc Natl Acad Sci U S A 104: , Harden RN, Bruehl S, Perez RS, Birklein F, Marinus J, Maihofner C, Lubenow T, Buvanendran A, Mackey S, Graciosa J, Mogilevski M, Ramsden C, Chont M, Vatine JJ: Validation of proposed diagnostic criteria (the Budapest Criteria ) for Complex Regional Pain Syndrome. Pain 150: , Helmberg W, Lanzer G, Zahn R, Weinmayr B, Wagner T, Albert E: Virtual DNA analysis a new tool for combination and standardised evaluation of SSO, SSP and sequencing-based typing results. Tissue Antigens 51: , Holzer P: Neurogenic vasodilatation and plasma leakage in the skin. Gen Pharmacol 30:5-11, Howson JM, Walker NM, Clayton D, Todd JA: Confirmation of HLA class II independent type 1 diabetes associations in the major histocompatibility complex including HLA-B and HLA-A. Diabetes Obes Metab 11(Suppl 1):31-45, Kemler MA, van de Vusse AC, van den Berg-Loonen EM, Barendse GA, van KM, Weber WE: HLA-DQ1 associated with reflex sympathetic dystrophy. Neurology 53: , Klein J, Sato A: The HLA system. First of two parts. N Engl J Med 343: , Kohr D, Singh P, Tschernatsch M, Kaps M, Pouokam E, Diener M, Kummer W, Birklein F, Vincent A, Goebel A, Wallukat G, Blaes F: Autoimmunity against the beta(2) adrenergic receptor and muscarinic-2 receptor in complex regional pain syndrome. Pain 152: , Krensky AM: The HLA system, antigen processing and presentation. Kidney Int Suppl 58:S2-S7, Marinus J, Moseley GL, Birklein F, Baron R, Maihofner C, Kingery WS, van Hilten JJ: Clinical features and pathophysiology of complex regional pain syndrome. Lancet Neurol 10: , Oliveira AL, Thams S, Lidman O, Piehl F, Hokfelt T, Karre K, Linda H, Cullheim S: A role for MHC class I molecules in synaptic plasticity and regeneration of neurons after axotomy. Proc Natl Acad Sci US A 101: , Robinson J, Mistry K, McWilliam H, Lopez R, Parham P, Marsh SG: The IMGT/HLA database. Nucleic Acids Res 39: D1171-D1176, Shiina T, Hosomichi K, Inoko H, Kulski JK: The HLA genomic loci map: Expression, interaction, diversity and disease. J Hum Genet 54:15-39, Spurkland A, Ingvarsson G, Falk ES, Knutsen I, Sollid LM, Thorsby E: Dermatitis herpetiformis and celiac disease are both primarily associated with the HLA-DQ (alpha 1*0501, beta 1*02) or the HLA-DQ (alpha 1*03, beta 1*0302) heterodimers. Tissue Antigens 49:29-34, Svejgaard A, Ryder LP: HLA and disease associations: Detecting the strongest association. Tissue Antigens 43:18-27, Tjon JM, van BJ, Koning F: Celiac disease: How complicated can it get? Immunogenetics 62: , Uibo R, Tian Z, Gershwin ME: Celiac disease: A model disease for gene-environment interaction. Cell Mol Immunol 8: 93-95, van de Beek WJ, Roep BO, van der Slik AR, Giphart MJ, van Hilten BJ: Susceptibility loci for complex regional pain syndrome. Pain 103:93-97, van Hilten JJ, Blumberg H, Schwartzman RJ: Factor IV: Movement disorder and dystrophy - pathophysiology and measurement, in Wilson PR, Stanton-Hicks M, Harden RM (eds): CRPS: Current Diagnosis and Treatment. Seattle, WA, IASP Press, 2005, pp

6 van Rooijen et al The Journal of Pain van Hilten JJ, van de Beek WJ, Roep BO: Multifocal or generalized tonic dystonia of complex regional pain syndrome: A distinct clinical entity associated with HLA-DR13. Ann Neurol 48: , van Rooijen DE, Geraedts EJ, Marinus J, Jankovic J, van Hilten JJ: Peripheral trauma and movement disorders: A systematic review of reported cases. J Neurol Neurosurg Psychiatry 82: , Vaneker M, van der Laan L, Allebes WA, Gorsi RJ: Genetic factors associated with complex regional pain syndrome 1: HLA DRB and TNF alpha promotor gene polymorphism. Disabil Med 2:69-74, Verduyn W, Doxiadis II, Anholts J, Drabbels JJ, Naipal A, D Amaro J, Persijn GG, Giphart MJ, Schreuder GM: Biotinylated DRB sequence-specific oligonucleotides. Comparison to serologic HLA-DR typing of organ donors in eurotransplant. Hum Immunol 37:59-67, Wesseldijk F, Huygen FJ, Heijmans-Antonissen C, Niehof SP, Zijlstra FJ: Six years follow-up of the levels of TNF-alpha and IL-6 in patients with complex regional pain syndrome type 1. Mediators Inflamm, 2008:Article ID , Zhernakova A, van Diemen CC, Wijmenga C: Detecting shared pathogenesis from the shared genetics of immunerelated diseases. Nat Rev Genet 10:43-55, 2009