Bone marrow plasma cells (BMPC) are mature white blood cells of the B-lymphocyte lineage that reside within the bone marrow. In a healthy state, these cells are responsible for producing antibodies to protect the body against infection.
In the context of Multiple Myeloma (MM), bone marrow plasma cells take on specific characteristics:
- Malignant Transformation: Multiple Myeloma is defined by the accumulation of malignant clonal plasma cells in the bone marrow. These cells often undergo DNA damage, leading them to grow out of control and crowd out healthy blood cells.
- Identification: These cells are typically identified in clinical samples by the expression of the CD138 marker.
- Abnormal Secretions: Unlike normal plasma cells, malignant BMPCs produce large amounts of a single, non-functional antibody known as monoclonal protein (M-protein) or “M-spike”.
The percentage of plasma cells found in the bone marrow is a critical diagnostic marker used to differentiate between various plasma cell disorders:
- Monoclonal Gammopathy of Undetermined Significance (MGUS): Characterized by having less than 10% BMPC.
- Smoldering Multiple Myeloma (SMM): Diagnosed when BMPC levels are between 10% and 59% in the absence of symptoms.
- Active Multiple Myeloma: Diagnosed when BMPC are 10% or greater (with accompanying CRAB symptoms or a plasmacytoma) or 60% or greater as a standalone “SLiM” criterion.
Furthermore, monitoring BMPC levels is essential for evaluating treatment response; for instance, a Complete Response (CR) requires bone marrow aspirates to show less than 5% plasma cells.
Synonyms
BMPC