Complex regional pain syndrome (CRPS) is a poorly understood condition where a person experiences persistent severe and debilitating pain.
Although most cases of CRPS are triggered by an injury, the resulting pain is much more severe and long-lasting than normal.
The pain usually only affects 1 limb, but it can sometimes spread to other parts of the body.
The skin of the affected body part can become so sensitive that a slight touch, bump or even a change in temperature can cause intense pain.
Affected areas can also become swollen, stiff or undergo fluctuating changes in colour or temperature.
CRPS often gradually improves over time. But some people with CRPS experience pain for many years.
You should see a GP if you have persistent pain that's preventing you from carrying out everyday activities.
Diagnosing CRPS can be difficult because it involves having tests to rule out other possible causes.
It's best to get help as soon as possible, as early treatment may help reduce your painful symptoms.
The cause of CRPS is unknown, but it's thought to be the result of the body reacting abnormally to an injury.
It used to be thought that CRPS was a psychosomatic condition, where the symptoms are "all in the mind", but research has disproved this.
It's difficult to estimate exactly how common CRPS is, as many cases may go undiagnosed or be misdiagnosed.
But it's thought to be fairly uncommon.
CRPS can begin at any age, including in children, although the average age for symptoms to start is around 50.
It's more common in women.
There's currently no cure for CRPS, but there are a number of treatments that can help manage the symptoms.
There are 4 main types of treatment:
Because of the complex nature of CRPS, a number of different healthcare professionals will usually be involved in your care.