Siblings’ Risk of Complex Regional Pain Syndrome

A group of Dutch scientists have been studying a condition called complex regional pain syndrome (CRPS). They are pulling together data to help us understand this painful problem. Their studies are carried out and reported through a group called TREND (Trauma RElated Neuronal Dysfunction). This study looks at the likelihood that a sibling(brother or sister) might develop the same condition.

Complex regional pain syndrome (CRPS) is a common problem after trauma to an arm or leg. The injury could be as a result of surgery or bone fracture. Distal radial (wrist) fractures are the most common injury leading to CRPS, but no one knows why this particular fracture leads to CRPS. CRPS can occur without any known trauma or injury. Non-traumatic cases of CRPS make up about 10 per cent of all affected patients.

No matter what the cause, the patient develops wrist and hand pain, swelling, and skin color changes. The pain and swelling are accompanied by a loss of motion and function. There can even be changes in skin temperature (warm or cold) and increased hair growth on the arm compared to the other (healthy) side. In one-third of all cases documented by TREND, more than one extremity (arm or leg) is affected. CRPS occurs in women much more often than men (75 to 85 per cent of all cases).

The question of whether there is a genetic link with CRPS has been raised by other studies. If that’s the case, then siblings might be at risk for CRPS if a brother or especially a sister develops CRPS. To find out, these Dutch scientists interviewed 405 patients already diagnosed with CRPS. They asked the patients how many siblings were in the family, if any of them had ever been diagnosed with CRPS, or if any of the brothers or sisters had ever had symptoms of CRPS.

Contact was made with 24 individuals out of the total 1,242 siblings who might be affected with CRPS. The physicians of these siblings were also asked to verify history, clinical presentation (signs and symptoms), and confirm a diagnosis of CRPS. Fractures and surgeries were the most common causes mentioned in the patients’ histories.

In order to tell if there is a link between family members with CRPS, a special mathematical formula was used to calculate the sibling recurrence risk ratio. They further assessed risk of siblings by the patient’s age (under 50 years old and 50 or older). Then they calculated the risk of developing CRPS for the general population and compared the results.

They found that the overall risk in the CRPS sibling group was the same as in the general population. In other words, the overall risk of developing CRPS if you have a brother or sister with this condition is no greater than your risk of developing CRPS when none of your siblings are affected. They did find that the patient’s age at the time of diagnosis may be a factor. Siblings of younger patients (less than 50 years old) with CRPS had a greater risk of developing CRPS. This finding in the subgroup by age may point to a genetic factor but further studies are needed to take a closer look at this link.

The authors concluded that this is the first study to look at the sibling recurrence risk ratio for patients with complex regional pain syndrome and their siblings. The CRPS problem is a complicated one that probably involves many factors, not just a genetic one. If there is a genetic link, it appears that it is more obvious in younger patients with CRPS.

There is always the question of whether the reason for CRPS in a sibling is environmental (the patient and sibling grew up together in the same home and were exposed to the same things). That is another area for future study. The authors suggest another study to confirm the findings in this sibling study first before expanding to investigate potential environmental factors.