Genetic factors are suggested to play a role in complex regional pain syndrome (CRPS). but familial Occurrence has not been extensively studied. In the present Study we evaluated familial occurrence in Dutch patients with CRPS. Families were recruited through the Dutch Association of CRPS patients and through referral by clinicians. The number of affected members per family, the phenotypic expression and inheritance were assessed. Demographic and clinical characteristics of familial CRPS(fCRPS) patients were compared with those of sporadic CRPS (sCRPS) patients from a Dutch population-based study and with a group of sCRPS patients that was proportionally matched for referral center of the fCRPS probandi to control for referral bias. Thirty-one CRPS families with two or more affected relatives were identified, including two families with five, four With four, eight With three and 17 with two affected relatives. In comparison with sCRPS patients, fCRPS patients had a younger age at onset and more often had Multiple affected extremities and dystonia. We conclude that CRPS may occur in a familial form, but did not find a clear inheritance pattern. Patients with fCRPS develop the disease at a younger age and have a. more severe phenotype than sporadic cases, suggesting a genetic predisposition to develop CRPS. (C) 2008 European Federation of Chapters of the International Association for the Study of Pain. Published by Elsevier Ltd. All rights reserved.