A 35-year-old woman is evaluated due to pain in the left lower extremity. The patient twisted her left ankle a month ago, and the initial pain and swelling gradually improved with rest and ibuprofen. However, over the next few weeks, she began experiencing worsening pain in the left foot, ankle, and lower calf. The pain is severe and constant, has a burning or stinging quality, and is worsened by movement. Vital signs are within normal limits. Examination shows erythema, warmth, and nonpitting edema of the left foot and leg extending up to midcalf. Light touch of the affected area elicits severe pain. There is decreased range of motion of the left ankle. The right lower extremity is normal, and the remainder of the examination shows no abnormalities. Blood cell counts, serum chemistry studies, and erythrocyte sedimentation rate are within normal limits. Left foot and ankle radiographs reveal patchy areas of osteopenia. Which of the following is the most likely diagnosis?

Question

A 35-year-old woman is evaluated due to pain in the left lower extremity.  The patient twisted her left ankle a month ago, and the initial pain and swelling gradually improved with rest and ibuprofen.  However, over the next few weeks, she began experiencing worsening pain in the left foot, ankle, and lower calf.  The pain is severe and constant, has a burning or stinging quality, and is worsened by movement.  Vital signs are within normal limits.  Examination shows erythema, warmth, and nonpitting edema of the left foot and leg extending up to midcalf.  Light touch of the affected area elicits severe pain.  There is decreased range of motion of the left ankle.  The right lower extremity is normal, and the remainder of the examination shows no abnormalities.  Blood cell counts, serum chemistry studies, and erythrocyte sedimentation rate are within normal limits.  Left foot and ankle radiographs reveal patchy areas of osteopenia.  Which of the following is the most likely diagnosis?

Quizplus · Accepted Answer

11ec25c8_d56a_b648_bc81_31f63471ca11_MD0003_00 This patient has subacute, severe, unilateral limb pain consistent with complex regional pain syndrome (CRPS) (previously known as reflex sympathetic dystrophy). CRPS often presents within 4-6 weeks following trauma (eg, fracture, sprain) or surgery, possibly due to effects of inflammatory cytokines (although the exact etiology is not well understood). It is characterized by burning or tingling pain out of proportion to the inciting event. The pain does not follow a dermatomal distribution and is typically worsened by movement or light contact (allodynia), which may lead patients to reduce activity. The diagnosis of CRPS is based primarily on clinical findings. In addition to sensory changes (allodynia, hyperesthesia), criteria include edema/sudomotor changes (eg, sweating) and vasomotor changes (eg, erythema, altered skin temperature). In advanced cases, trophic changes affecting skin, nails, and hair may be present, and patients may have motor weakness or contractures. X-ray often shows patchy demineralization, and bone scintigraphy may show increased uptake in the affected limb. Management of CRPS should emphasize exercise, physical/occupational therapy, and patient education. Comorbid depression and anxiety should be addressed. Medication options include nonsteroidal anti-inflammatory drugs and antineuropathic medications (primarily anticonvulsants [eg, pregabalin] and tricyclic antidepressants [eg, amitriptyline]). Bisphosphonates (eg, alendronate) and topical lidocaine and capsaicin may also be effective. (Choice A) Lymphedema can present as persistent swelling in the lower extremity, but it does not typically cause severe pain or allodynia. It may occur following proximal lower extremity trauma, but this patient's ankle sprain would be unlikely to lead to lymphedema. (Choice C) Deep venous thrombosis can cause swelling and redness, but it is typically acute and would not cause allodynia or patchy osteopenia. (Choice D) Peripheral arterial disease (PAD) can cause pain, trophic skin changes, and skin color changes, but it does not typically cause edema or allodynia. The pain (ie, intermittent claudication) typically occurs with exercise rather than simple movement. Symptomatic PAD would be unlikely in a young patient without underlying atherosclerotic risk factors. (Choice E) Peripheral neuropathy can cause allodynia and burning pain in the lower extremity but would not cause edema, erythema, or osteopenia. When neuropathy occurs in a regional (eg, stocking/glove) distribution, it is typically bilateral. (Choice F) Skin and soft tissue infection (eg, cellulitis) typically presents with acute erythema, swelling, and pain and would usually be associated with fever, leukocytosis, and elevated inflammatory markers (eg, erythrocyte sedimentation rate). It would not explain this patient's patchy osteopenia. Educational objective: Complex regional pain syndrome typically follows local trauma or surgery and is characterized by severe burning or tingling pain in a regional (not dermatomal) distribution. It is often associated with edema, erythema, and trophic skin, hair, or nail changes. X-ray may show patchy demineralization. References: Pathophysiological mechanisms involved in vasomotor disturbances in complex regional pain syndrome and implications for therapy: a review. (http://www.ncbi.nlm.nih.gov/pubmed/26547635) Complex regional pain syndrome: an optimistic perspective. (http://www.ncbi.nlm.nih.gov/pubmed/25471395)

A 35-Year-Old Woman Is Evaluated Due to Pain in the Left