The importance of bone marrow infiltration patterns in multiple myeloma seen on magnetic resonance imaging-Case report and imaging perspective.

Non-secretory multiple myeloma (NSMM) is an extremely rare variant of multiple myeloma (MM) and accounts for a maximum of 5% of all myeloma cases. This variant of MM usually represents a diagnostic challenge to the clinician because of the absence of detectable monoclonal immunoglobulin on serum or urine electrophoresis. We present the case of a 34-year-old Caucasian male who presented to the emergency department with pain in the lumbar area secondary to a fall and who was eventually diagnosed with non-secretory multiple myeloma after the radiologist initially pointed out a discrete "salt and pepper" infiltration of the spine seen on magnetic resonance imaging (MRI) although the spine computed tomography (CT) performed initially showed no suspicious lesions for malignancy. The final diagnosis was obtained after a positive bone marrow biopsy together with the presence of malignant lesions seen on the spine MRI. This case points out the importance of different bone marrow involvement patterns seen on MRI and other useful sequences the radiologist could use to better discriminate between normal marrow reconversion and malignant infiltration.