Pathology
Plasma Cell Disorders
Plasma cell disorders for MBBS and NEET-PG: multiple myeloma pathology, M protein, Bence Jones proteinuria, lytic bone lesions, MGUS and Waldenstrom macroglobulinaemia, mapped to NMC code PA20.1.
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Plasma Cell Disorders
Plasma cell disorders for MBBS and NEET-PG: multiple myeloma pathology, M protein, Bence Jones proteinuria, lytic bone lesions, MGUS and Waldenstrom macroglobulinaemia, mapped to NMC code PA20.1.
This chapter covers the plasma cell disorders, dominated by multiple myeloma. It describes the pathology, genetics, clinical features and laboratory findings, including the monoclonal protein, Bence Jones proteinuria, lytic bone lesions and renal involvement, and the related conditions of MGUS and Waldenstrom macroglobulinaemia.
High-yield: Plasma Cell Disorders
- Multiple myeloma is a malignant clonal proliferation of plasma cells in the bone marrow.
- The classic tetrad of myeloma is hypercalcaemia, renal impairment, anaemia and bone lesions.
- Myeloma produces a monoclonal immunoglobulin (M protein), most often of the IgG or IgA type.
- Bence Jones protein is free immunoglobulin light chain in the urine, not detected by standard dipstick.
- The bone lesions of myeloma are punched-out lytic areas, classically seen in the skull.
- Rouleaux formation on the blood film reflects the high immunoglobulin level in myeloma.
- Serum and urine protein electrophoresis show an M band, and immunofixation identifies the immunoglobulin class.
- The bone marrow in myeloma shows more than 10% plasma cells, sometimes with atypical or flame cells.
- Renal failure in myeloma is caused by light chain (cast) nephropathy, hypercalcaemia and amyloidosis.
- Myeloma predisposes to infection because normal immunoglobulin production is suppressed.
- Monoclonal gammopathy of undetermined significance is a symptom-free M protein that may progress to myeloma.
- Waldenstrom macroglobulinaemia is an IgM-secreting lymphoplasmacytic lymphoma that causes hyperviscosity.
- AL amyloidosis, a complication of plasma cell disorders, results from deposition of immunoglobulin light chains.
- A solitary plasmacytoma is a single mass of clonal plasma cells that may later progress to myeloma.
Multiple myeloma essentials
- **Clinical tetrad:** Hypercalcaemia, renal impairment, anaemia and bone (lytic) lesions.
- **M protein:** Monoclonal immunoglobulin, usually IgG or IgA, seen as an M band on electrophoresis.
- **Bence Jones:** Free light chains in urine; missed by standard dipstick.
- **Marrow:** More than 10% clonal plasma cells; rouleaux on the film.
NMC competencies in this chapter
- **PA20.1:** Pathology, genetics, clinical features and laboratory findings of plasma cell disorders
Frequently Asked Questions
What is the clinical tetrad of multiple myeloma?
Hypercalcaemia, renal impairment, anaemia and lytic bone lesions, often remembered as CRAB.
What is Bence Jones protein?
Free immunoglobulin light chain excreted in the urine, which is not detected by standard dipstick and needs electrophoresis or immunofixation.
Why do myeloma patients get infections?
Because the malignant clone suppresses normal immunoglobulin production, leaving the patient with functional hypogammaglobulinaemia.
What is MGUS?
Monoclonal gammopathy of undetermined significance, a symptom-free monoclonal protein that carries a small annual risk of progressing to myeloma.
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