Multiple myeloma associated with extramedullary plasmacytoma at initial presentation is rare. We describe a 45-year-old female patient with an initial presentation of low back pain and right side L5, S1 radiculopathy. There was no evidence of vertebral involvement but an epidural tumor was found later during neurosurgical intervention. The final diagnosis was immunoglobulin G, kappa multiple myeloma complicated with spinal root compression by an extramedullary plasmacytoma. No osteolytic lesion was noted over the length of the spine. Pathology revealed high-grade plasmablastic myeloma. During the clinical course, the patient was refractory to induction chemotherapy, and there was progressive deterioration of renal function. Urinary tract infection by Morganella morganii and pulmonary infection of unknown cause developed 5 months later, and the patient died.