Bonepain is one of the most common chief complaints. It can be a simple problem or an initial symptom of a more complex and serious disease. In older patients with non-traumatic bonepain that does not improve with conventional treatment, differential diagnosis with multiple myeloma, among others, is required. We present the case of an 83-year-old woman with bonepain in lower limb of several months' duration that does not improve with pain medications. X-ray reveal lytic lesion in her left femur and mediastinal widening related to sternal plasmacytoma causing cardiac compression. A complementary study confirmed the diagnosis of multiple myeloma