Complex regional pain syndrome (CRPS) is a rare disorder of the sympathetic nervous system. It used to be called reflex sympathetic dystrophy (RSD). It causes chronic severe burning pain anywhere in the body, but usually affects the arms, fingers, palm of hand, shoulder, or legs. If not treated, the pain and weakness may lead to limited use of that body part.

There are 2 types. They only vary depending on if you have had nerve injury. Both have the same symptoms and outcome. They are:

• CRPS type 1. This happens after injury or illness with no specific nerve damage.
• CRPS type 2. This happens after a specific nerve injury. CRPS type 2 used to be called causalgia.

The cause of CRPS is not known. An injury may cause CRPS. It can be something minor, such as a sprain or a cut. Or it may be more severe, such as a bone break. Or it may be linked to a surgery, such as carpal tunnel release. As you're healing, you may feel new, severe pain in the injured area. That pain may spread through the injured limb. Over time, other symptoms may appear.

If you aren't treated soon, the symptoms of CRPS can get worse or change over time. Below are symptoms that can occur in the body part that is affected.

Symptoms include:

• Ongoing, severe, burning pain.
• Being sensitive to touch (pain from physical contact that normally is not painful).
• Swollen, blotchy, reddish, or purple skin.
• Stiff joints.
• Change in temperature of the body part.
• Abnormal sweating in the body part or nearby areas.

Symptoms include:

• Skin that appears shiny and thin.
• Loss of muscle strength.
• Changes in hair and nail growth.
• Ridges in skin look flatter than normal.
• Shrinking of the affected limb.
• Constant swelling of the foot or hand.
• Spreading to other limbs.
• Abnormal movements of the limb, such as poor coordination, tremor, and movements you can't control.