Peripheral neuropathies secondary to genetic abnormalities, diabetes mellitus, uremia, alcoholism, etc. can include symptoms of burning pain, allodynia, hyperalgesia, and sudomotor and vasomotor changes. However, symptoms are symmetrical, tend to begin in distal lower limbs, and affect upper extremities later and not as severely. If large (A alpha beta) nerve fibers are affected, there are loss of reflexes, weakness, and vibratory and proprioceptive deficits. Trauma is absent, and most peripheral neuropathies progress gradually. However, in a study of the specificity of the 1993 IASP CRPS criteria, Galer and colleagues found that up to 37% of patients with painful diabetic neuropathy met the clinical criteria of CRPS (Galer et al 1998). Focal or entrapment neuropathies such as carpal tunnel, cubital tunnel, or thoracic outlet syndromes are not usually associated with trauma and progress gradually, and symptoms and signs are confined to specific nerve(s) distributions.
Vascular abnormalities such as deep vein thrombosis or thrombophlebitis can cause swelling, pain, temperature changes, and discoloration (erythema) of the affected extremity. Unilateral arterial insufficiency can also be painful with clinical signs similar to CRPS. Ultrasonography is necessary to diagnose these vascular conditions. Lymphedema secondary to surgery, radiation, or infection develops insidiously, and pain is usually of an aching quality. It can be diagnosed with lymphoscintigraphy. Also, focal joint inflammatory diseases such as gout, pseudogout, tenosynovitis due to arthropathy, as well as scleroderma must be considered. Of note, 3 patients presenting with CRPS were found to have an underlying peripheral nerve vasculitis responsive to immunomodulative therapy (Ramchandren et al 2008).