The Missing M Band: Is it Really Non Secretory Multiple Myeloma?

Abstract

Background: Non-secretory multiple myeloma (NSMM) is defined as clonal bone marrow plasma cells ≥10% or biopsy proven plasmacytoma, evidence of end-organ damage due to underlying plasma cell dyscrasia, namely hypercalcemia, renal insufficiency, anaemia, bone lesions and lack of serum and urinary monoclonal protein on electrophoresis and immunofixation. They represent 3-5% of multiple myeloma (MM). With the advent of serum free light chain (s FLC) measurement, most of NSMMs have been classified as Light chain Multiple myeloma (LCMM). Thus, the proportion of true NSMM, meaning MM that secretes no monoclonal protein (complete immunoglobulin, heavy or light chain) is close to 1-2% of all myelomas. There is a need to distinguish between the true non-secretory from the other forms of oligo-secretory (OSMM) and secretory form of myeloma like LCMM with use of advanced diagnostic tools such as s FLC assay as the former has a good prognosis.

Case presentation: We discuss a case of a 65-years-old female who presented with chronic chest pain since one year. Cardiac and musculoskeletal involvement were ruled out. Monoclonal gammopathy was suspected in view of imaging abnormalities. Surprisingly, SPE and IFE reported absence of M band. A provisional diagnosis of NSMM was made based on biopsy features. However, diagnosis of NSMM was later changed to LCMM in view of a positive sFLC ratio.

Conclusions: It is well-known that the sequence of diagnostic investigations plays a crucial role in the timely diagnosis and management of patients. However, in this case it was a faulty sequence of ordering investigations which prolonged the hospital stay and delayed therapeutic intervention for the patient concerned. Serum Protein Electrophoresis (SPE), Immunofixation electrophoresis (IFE) and sFLC are simple blood-based tests which can help diagnose a majority of cases of monoclonal gammopathies. They need to be included as first line tests in our approach to evaluating a suspected case of monoclonal gammopathy.

Keywords: Non- secretory Multiple myeloma; Oligo-secretory multiple myeloma; case report; light chain multiple myeloma; serum -free light chain assay.

Figure 1:

Radiological findings A) lateral skull radiograph showing multiple punched out lytic lesions of variable sizes in the calvarium as well the mandible B) frontal knee radiograph showing lytic lesions in both femur and tibia C) Sagittal reformatted CT thoracic spine image showing diffuse osteopenia and lytic lesions of the entire visible spine as well as the sternum, wedging and collapse of multiple vertebrae is evident D) CT guided bone biopsy procedure from a lesion of the left ilium E) Sagittal T1W image of the lumabosacral spine, F) Sagittal whole spine T2W image, and G) Sagittal post contrast fat-suppressed T1W image showing replacement of the vertebral marrow with poorly defined lesions, some of them showing enhancement, and the multi-level vertebral collapse H) Sagittal T2W, and I) Sagittal post contrast fat suppressed T1W images six-months after the first MRI, showing further progression of the disease, with extensive marrow replacement, enhancement and vertebral collapse.

Figure 2:

Serum protein electrophoresis reveals absence of M band.

Figure 3:

Algorithm suggested for evaluation of suspected cases of Monoclonal Gammopathy.