Q: I have had great difficulty finding information on immersion syndrome, which I believe is a form of reflex sympathetic dystrophy (RSD). Since RSD is a manifestation of autonomic dysfunction, isn’t immersion syndrome also a matter of autonomic dysfunction?
—Steven Klein, DO, MPH, Gloucester City, N.J.

A: Immersion syndrome (also referred to as “immersion foot” or “trench foot”) is a nonfreezing peripheral cold injury caused by prolonged or repetitive exposure to damp, cold temperatures (cool or cold water or mud). The extremity first becomes cold, numb, pale, edematous, and clammy. This is followed by blistering that progresses to ulceration and gangrene and can be complicated by infection. The long-term effects are thought to be due to autonomic disturbance and include hyperhidrosis, pain, and hypersensitivity to temperature changes.

RSD, which comes under the umbrella of complex regional pain syndrome (CRPS), is a sympathetically mediated pain that follows injury to bone and soft tissue or a vascular event, such as MI or stroke. Like immersion syndrome, RSD can include pain associated with autonomic changes, such as sweating or vasomotor abnormalities, but RSD can also have accompanying dystrophic changes, such as patchy bone demineralization or joint contractures. Although the pathogenesis of RSD is not well elucidated, it is thought to involve a reflex arc that includes the central nervous system (Pain. 1995;63:127-133). So, in answer to your question, immersion syndrome is not classified under RSD, although there are some similarities and both do involve autonomic dysfunction.
—Susan Kashaf, MD, MPH (98-13)

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