IgA multiple myeloma-associated mediastinal spinal plasmacytoma presenting as spinal cord compression.

Multiple myeloma associated with extramedullary plasmacytoma at initial presentation is rare. We describe a case of a man in his 30s who initially presented with symptoms of spinal cord compression. Further imaging revealed a mediastinal tumour, with a biopsy confirming plasmacytoma. Immunofixation revealed IgA lambda paraprotein. Bone marrow biopsy demonstrated atypical T-cell cytotoxic proliferation and trilineage hypoplasia. The patient was diagnosed with extramedullary plasmacytoma with active IgA multiple myeloma. The patient received mediastinal radiation to the tumour, followed by anti-myeloma therapy. This diagnosis is critical as managing a solitary plasmacytoma drastically differs from an extramedullary plasmacytoma with active multiple myeloma.