Atypical imaging feature of non-secretory multiple myeloma

Non-secretory multiple myeloma (NSMM) is a rare variant of the classic form of multiple myeloma in which no monoclonal gammopathy can be demonstrated in the serum or urine. We describe a rare case of non-secretory multiple myeloma in a 23 year old female presenting with bilateral limb weakness of two years duration. Clinically she was diagnosed to have Pott's spine and was treated with category 1 anti tubercular drugs. Hematological investigations showed plasmacytosis and radiography showed osteolytic lesions. No monoclonal gammopathy was found in the serum or urine. MRI showed multiple compressions with sclerosis within vertebral bodies suggestive of osteomalacia/ diffuse infiltrative disorder. The free light chain (FLC) assay revealed increment in the free kappa light chain and an abnormal κ/λ ratio. Free Light Chain assay (FLC) when used in complement with Protein Electrophoresis (PEP) and Immunofixation Electrophoresis (IFE) were pivotal in diagnosis of non secretory multiple myeloma or light chain myelomas. FLC is a useful monitoring tool because it reflects therapy results due to short serum half life.