[An unusual case of multiple myeloma diagnosed by a noticeable decrease in the serum M-component level]

Area of Science:

• Hematology
• Oncology
• Immunology

Background:

• Monoclonal gammopathy of undetermined significance (MGUS) can progress to multiple myeloma.
• Multiple myeloma is characterized by the proliferation of malignant plasma cells.
• Serum monoclonal protein levels and Bence Jones proteins in urine are key diagnostic markers.

Observation:

• A 61-year-old woman initially diagnosed with MGUS later developed indolent multiple myeloma.
• The patient exhibited a decrease in serum monoclonal IgG (kappa) levels concurrently with Bence Jones protein escape.
• Bone marrow examination revealed immature plasma cells, and immunofluorescence showed distinct subpopulations of plasma cells.

Findings:

• Myeloma cells demonstrated immunologically diverse subpopulations: some producing IgG (kappa) and others producing only kappa light chains.
• Approximately two-thirds of plasma cells showed this dual population characteristic.
• This specific pattern of Bence Jones escape associated with a decrease in serum M-component was previously undescribed.

Implications:

• The findings suggest that multiple myeloma can evolve from a single clone into heterogeneous subpopulations.
• This heterogeneity may impact treatment strategies and disease monitoring in multiple myeloma.
• Understanding these diverse myeloma cell subpopulations is crucial for accurate diagnosis and prognosis.