Reflex sympathetic dystrophy may occur in either the upper or lower limbs. The clinical course moves in stages:
There is no useful laboratory testing in this syndrome. Majority of the diagnosis will come from the history and physical exam. Plain radiographs will show pronounced demineralization of the skeleton affected by the pain and edema. This worsens as the disease progresses.
Bone radionuclide test may be useful in early disease, but findings are not specific for this condition. Magnetic resonance imaging (MRI) may be useful in identifying patients, as it gives useful information on the soft tissue and skin changes. CT scans may show multiple focal areas of osteoporosis.
Autonomic testing like resting skin temperature and resting sweat output may be done to document the vasomotor symptoms. An increased resting skin temperature is highly suggestive of this disease .
There are two major therapies being used currently. There is insufficient data on other effective therapies and little randomized control studies.
Other treatments such as non steroidal anti-inflammatory drugs (NSAIDs) may be used. Corticosteroids are highly effective in reducing pain and allowing for physical therapy. Surgical methods may be used and include thoracic or lumber sympathectomy. This is indicated in cases resistant to therapy. Surgery should be considered before there is significant joint deformity. Chemical sympathectomy with alcohol has also been done.
The course of the disease is variable, but if caught early and treated appropriately, many patients do not progress on to the later stages of the disease. There is little data on mortality, but morbidity may be significant.
Reflex sympathetic dystrophy usually occurs after injury, which can be traumatic or postsurgical. In some cases there may be no identifiable incident. In some patients an event such as myocardial ischemia or a hemiplegic stroke, may be the inciting event. Common surgical procedures such as arthroscopy of the knee and other joints may be the cause in some patients. There also have been cases in diseases such as pancreatic and pancoast tumors  .
35% of patients have no identifiable inciting event. There is an estimated 5% prevalence in people with a previous upper extremity injury. The syndrome was prevalent (12%) in patients with hemiplegic stroke, but this has significantly decreased with the advent of early mobilization. There is no gender or race predilection, but it has a peak incidence between 30 to 60 years .
There appears to be a need of three conditions to be present for reflex sympathetic dystrophy to occur:
The true mechanism of this complex regional pain syndrome is unclear, but appears to involve the formation of a new reflex arc after the inciting event. The arc follows a sympathetic pathway and is then modulated by cortical centres and produces vascular changes. The pain occurs possibly due to the triggering event causing nerve damage with increased sensitivity to sympathetic neurotransmitters such as epinephrine.
There is thought to be prolonged and constant release of pain inciting peptides from peripheral nerves causing nerve inflammation with subsequent pain and allodynia. Neuropeptide Y and substance P have been implicated in this. There appears to be a genetic predisposition. A few human leukocyte antigen (HLA) associations have been found, a few examples include HAL-A3, and DR2  .
Quick physiotherapy and mobilization has been noted to reduce the incidence, especially in patient with hemiplegic strokes. Early mobilization is advised when possible after any intervention or injury of limb, to reduce the occurrence of this disease.
There are two types of a complex regional pain syndrome (CRPS):