Pathology Cheat Sheet
Separate Monoclonal States
Monoclonal gammopathy for NEET-PG: MGUS vs smouldering vs myeloma CRAB, M protein spike, Bence Jones protein, Waldenstrom IgM, and serum free light chains.
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Separate Monoclonal States
Monoclonal gammopathy for NEET-PG: MGUS vs smouldering vs myeloma CRAB, M protein spike, Bence Jones protein, Waldenstrom IgM, and serum free light chains.
The spectrum of plasma cell disorders from benign monoclonal gammopathy through smouldering to symptomatic myeloma and related entities.
High-yield lines
- Plasma cell disorders are clonal proliferations that secrete a monoclonal immunoglobulin, the M protein.
- The M protein appears as a sharp spike in the gamma region on serum protein electrophoresis.
- Monoclonal gammopathy of undetermined significance (MGUS) has an M protein below 3 grams per decilitre and under 10 percent marrow plasma cells without end-organ damage.
- Smouldering myeloma has higher tumour burden than MGUS but no end-organ damage.
- Symptomatic multiple myeloma is defined by end-organ damage summarised as CRAB: hypercalcaemia, renal failure, anaemia, and bone lesions.
- MGUS progresses to myeloma at roughly one percent per year.
- Waldenstrom macroglobulinaemia is a lymphoplasmacytic lymphoma secreting monoclonal IgM causing hyperviscosity.
- Bence Jones protein is free monoclonal light chain in the urine.
- Free light chains deposit in the kidney and can cause AL amyloidosis.
- A solitary plasmacytoma is a single mass of clonal plasma cells that may progress to myeloma.
- POEMS syndrome combines polyneuropathy, organomegaly, endocrinopathy, an M protein, and skin changes.
- Serum free light chain ratio and immunofixation help characterise and distinguish these monoclonal states.
Mapped competency codes
- PA20.1
Continue into the full chapter
This summary maps to PA20-plasma-cell-disorders.
Frequently Asked Questions
What distinguishes MGUS from multiple myeloma?
MGUS has an M protein below 3 grams per decilitre and fewer than 10 percent marrow plasma cells with no end-organ damage, whereas myeloma shows CRAB end-organ damage and higher tumour burden.
What are the CRAB features of symptomatic myeloma?
Hypercalcaemia, renal failure, anaemia, and lytic bone lesions, which define end-organ damage requiring treatment.
What is Waldenstrom macroglobulinaemia?
A lymphoplasmacytic lymphoma that secretes monoclonal IgM, causing hyperviscosity symptoms rather than the lytic bone disease of myeloma.
What is Bence Jones protein?
Free monoclonal immunoglobulin light chain excreted in the urine, characteristic of plasma cell disorders such as multiple myeloma.
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