Acrometastasis as a mimic of complex regional pain syndrome.

Introduction: Complex regional pain syndrome (CRPS) is characterized by chronic pain disproportional to any inciting event, and is associated with poor quality of life, and large clinical, healthcare, and societal costs. A CRPS diagnosis is challenging due to the lack of biomarkers and objective laboratory and radiographic tests. CRPS is currently diagnosed according to the IASP clinical diagnostic criteria, and it is not a radiological diagnosis. We report a case of acrometastasis to the hand that was initially thought to be CRPS. The purpose of this publication is to reinforce the importance of CRPS to be a diagnosis of exclusion.

Case Presentation: A woman in her 70s presented to a primary care facility with moderate pain in the dorsum of her right wrist and hand that began approximately two weeks prior without trauma. The initial reading of the white blood cell scan and three-phase bone scan (TPBS) were suggested to be compatible with CRPS; however, a pain medicine specialist did not confirm the diagnosis. The patient was later diagnosed with acrometastasis as a result of a bone biopsy demonstrating metastatic lung adenocarcinoma.

Conclusion: CRPS shares clinical indications with various inflammatory diseases. Imaging techniques cannot be solely utilized to diagnose CRPS due to nonuniform findings and not only low but varying sensitivity and specificity. The WBC scan, laboratory results, and the three-phase bone scan did not properly demonstrate CRPS. Our case demonstrates the importance of excluding all conditions with similar presentations prior to determining a CRPS diagnosis and understanding the importance of interpreting a TPBS.