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Complex regional pain syndrome

Complex regional pain syndrome, or CRPS, causes a person to have a constant burning pain in a limb: one of the arms, legs, hands, feet or ankles.

The condition cannot be cured, but the symptoms can be managed.

It isn't fully known what causes CRPS, but it seems to be a problem with the way the body's nervous system responds to an injury.

CRPS affects around 1 in 3,800 people in the UK. It can affect people of any age, but it usually begins after 40.

What causes complex regional pain syndrome?

Doctors believe CRPS does not have a single cause but results from multiple causes that produce similar symptoms. Some theories suggest that pain receptors in the affected part of the body become responsive to catecholamines, a group of nervous system messengers. In cases of injury-related CRPS, the syndrome may be caused by a triggering of the immune response that may lead to the inflammatory symptoms of redness, warmth, and swelling in the affected area. For this reason, it is believed that CRPS may represent a disruption of the healing process.

What are the symptoms of CRPS?

The symptoms of CRPS vary in their severity and length. One symptom of CRPS is continuous, intense pain that gets worse rather than better over time. If CRPS occurs after an injury, it may seem out of proportion to the severity of the injury. Even in cases involving an injury only to a finger or toe, pain can spread to the entire arm or leg. In some cases, pain can even travel to the opposite extremity. Other symptoms of CRPS include:

  • Painful burning sensation.
  • Swelling and stiffness in affected joints.
  • Motor disability with reduced ability to move the affected part of the body.
  • Changes in nail and hair growth patterns. There may be rapid hair growth or no hair growth.
  • Skin changes. CRPS involves changes in skin temperature - skin on one extremity can feel warmer or cooler compared to the opposite extremity. Skin colour changes also are apparent, as the skin is often blotchy, pale, purple or red. The texture of skin also can change, becoming shiny and thin. People with CRPS may have skin that sometimes is excessively sweaty.

CRPS may be heightened by emotional stress.

How is complex regional pain syndrome diagnosed?

A doctor will carry out a physical examination and ask about symptoms and any injury.

Tests that may indicate CRPS include:

  • Physical examination, looking for swollen joints, changes to skin temperature and appearance
  • Sweat testing, looking for differences between readings on an affect limb and another limb
  • Thermography, infrared thermometer readings of affected limb's skin temperature
  • Electrodiagnostic testing of electrical activity of the nerves


Other tests may include:

  • Blood tests to rule out infection or rheumatoid arthritis
  • MRI to rule out tissu or bone problems
  • Biopsy tissue sample checking for abnormal cells
  • X-ray to rule out joint and bone problems.
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