Increased risk of complex regional pain syndrome in siblings of patients?

UNLABELLED: An increased risk among siblings of probands with complex regional pain syndrome (CRPS) may be indicative of a genetic contribution. We calculated the sibling recurrence risk ratio (lambda(sibling)), a measure of familial aggregation. We surveyed 405 CRPS patients to collect information on the occurrence of CRPS in their siblings and compared this risk with the population risk to develop the syndrome. Information on disease status was collected from 1242 siblings, of which 24 were possibly affected according to their siblings. The diagnosis was confirmed in 16 patients, rejected in 2, and could not be verified in the remaining 6. Age-specific risk ratios were calculated for younger (<50 years) and older (> or =50 years) age groups. The strongest effects were seen in the younger age group, with a lambda(sibling) for possibly affected and confirmed cases of 5.6 (95% CI, 3.0 to 9.8) and 3.4 (95% CI, 1.5 to 6.8), respectively. We concluded that this study yielded no indications for an overall increased risk of developing CRPS for siblings of CRPS patients but that the risk was significantly increased in siblings younger than 50, which may indicate that genetic factors play a more pronounced role in this subgroup. PERSPECTIVE: We studied the risk of developing CRPS for siblings of patients with this syndrome. Although the overall risk for siblings was not increased compared with the population risk, the risk for younger siblings was elevated. To enhance chances of success, future genetic studies may consider restricting inclusion to younger-onset cases.