Question:medium
A 50 year old woman has a history of a sprained ankle 2 months back followed by apparent recovery. She now complains of severe pain in that ankle with inability to flex the foot. On local examination the physician notes edema and shiny skin. What is the probable diagnosis?
A 50 year old woman has a history of a sprained ankle 2 months back followed by apparent recovery. She now complains of severe pain in that ankle with inability to flex the foot. On local examination the physician notes edema and shiny skin. What is the probable diagnosis?
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Disproportionate regional pain plus shiny skin after a sprain with no named nerve injury equals CRPS type 1.
Updated On: Jun 24, 2026
- Fibromyalgia
- Complex regional pain syndrome type 1
- Complex regional pain syndrome type 2
- Peripheral neuropathy
Show Solution
The Correct Option is B
Solution and Explanation
Start from the timeline. A minor ankle sprain should settle within a few weeks, yet two months later this patient has worsening, severe, regionally confined pain that is far out of proportion to the trivial original trauma. Layered on top of the pain are objective changes confined to the same limb: swelling and abnormally shiny skin. That combination of out-of-proportion pain plus autonomic and trophic skin changes is the signature of complex regional pain syndrome.
The only remaining decision is which subtype. The two subtypes are separated by a single question: was there a real nerve injury? If a specific peripheral nerve was damaged, it is CRPS type 2 (causalgia). If the triggering event was trauma but no major nerve lesion can be pinned down, it is CRPS type 1 (the older term being reflex sympathetic dystrophy). An ordinary ligamentous ankle sprain damages soft tissue, not a named nerve, so this is type 1.
The distractors do not fit: fibromyalgia is a diffuse, bilateral pain disorder without trophic skin change, and a peripheral neuropathy produces a symmetrical sensory deficit rather than a shiny, swollen, exquisitely painful single ankle.\[\boxed{\text{Complex regional pain syndrome type 1}}\]
The only remaining decision is which subtype. The two subtypes are separated by a single question: was there a real nerve injury? If a specific peripheral nerve was damaged, it is CRPS type 2 (causalgia). If the triggering event was trauma but no major nerve lesion can be pinned down, it is CRPS type 1 (the older term being reflex sympathetic dystrophy). An ordinary ligamentous ankle sprain damages soft tissue, not a named nerve, so this is type 1.
The distractors do not fit: fibromyalgia is a diffuse, bilateral pain disorder without trophic skin change, and a peripheral neuropathy produces a symmetrical sensory deficit rather than a shiny, swollen, exquisitely painful single ankle.\[\boxed{\text{Complex regional pain syndrome type 1}}\]
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