Differential diagnostics are intended to differentiate multiple myeloma from other malignant diseases with bone marrow involvement, chronic inflammation conditions, and lymphoproliferative diseases.
A M-component with < 30 g/l and < 10 % plasma cells in bone marrow biopsy which is not accompanied by symptoms, biomarkers or signs of multiple myloma or other B-lymphoproliferative disease is called MGUS (monoclonal gammopathy of undetermined significance).
The differentiation between MGUS and smouldering multiple myloma is based on the size of the M-component and/or amount of plasma cells in the bone marrow. However, there is no indication for treatment until (symptomatic) multiple myeloma is present.
MGUS is relatively common (up to 3% in people over 50). Thus, most persons having M-protein in their serum have MGUS and not cancer of the bone marrow.
Other conditions where the M-protein may be present are:
- Solitary plasmacytoma
- B-cell non-Hodgkin lymphoma (including Waldenström macroglobulinemia)
- Chronic lymphatic leukemia
- Autoimmune disease such as SLE