Progressive lower extremity weakness as the initial presentation of isolated large thoracic plasmacytoma

Plasmacytoma is a tumor of monoclonal plasma cells of bone or soft tissue that can occur anywhere in the body without evidence of systemic multiple myeloma. It may present as solitary or multiple masses and is classified as osseous if arising from bone or extraosseous if arising from soft tissue. Osseous plasmacytoma is the most common form of plasmacytoma with predominance in active hematopoietic bones, including vertebrae, femur, pelvis, and ribs. The diagnosis is made with a tissue biopsy. Different imaging modalities allow for tumor localization, and magnetic resonance imaging (MRI) is the gold standard to detect spinal cord compression. Corticosteroids provide analgesia, reduce vasogenic edema, and have anti-myeloma activity which may result in better neurological outcomes in cases of acute spinal cord compression. Corticosteroids should be started promptly once cord compression is suspected. We report a case of progressive lower extremity weakness as the initial presentation of a thoracic plasmacytoma. The patient was started on a high-dose corticosteroid after acute cord compression was suspected. Magnetic resonance imaging confirmed cord compression. T1-T2 corpectomy with C5-T5 posterior spinal fusion for decompression and stabilization was done. He was successfully discharged to an inpatient rehabilitation facility with plans for definitive radiotherapy. Worsening back pain and lower extremity weakness in elderly patients should raise concerns for acute cord compression. Early intervention to relieve compression is crucial to preserve neurological functions.   Keywords: plasmacytoma, weakness, steroids, multiple myeloma