Plasma Cell Dyscrasias Flashcards
Where do B cells come from and what is their function?
Derived from stem cells in the bone marrow
- produce antibodies
What are antibodies and how are they structured?
Immunoglobulins
- -> proteins made of 2 heavy chains + 2 light chains
- monomers = IgD, IgE + IgG
- dimer = IgA
- pentamer = IgM
Describe the progression of a stem cell into a plasma cell
Stem cell –> lymphoid progenitor –> pro B cell –> pre B cell –> (leaves marrow) –> IgM B cell –> IgM plasma cell
(may return to marrow as plasma cell or circulate as memory B cell)
What is the function of a plasma cell and what does it look like?
Factory cell –> pumps out antibody
Clock-face nucleus, plentiful blue cytoplasm, pale patch next to nucleus
What might cause a polyclonal rise in Ig?
Reactive to –> infection, AI, malignancy, liver disease
What would cause a monoclonal rise in Ig?
Underlying clonal B cell disorder
What is another term for monoclonal Ig?
Paraprotein
Which investigations defect monoclonal Ig?
Serum electrophoresis –> detects abnormal protein bands
Serum immunofixation –> classifies abnormal band e.g. IgG, IgM
What is Bence Jones protein and how is it detected?
Excess Ig light chains in urine
–> detected by urine electrophoresis
What are the possible causes of paraproteinaemia?
MGUS (monoclonal gammaopathy of uncertain significance) Myeloma Amyloidosis Lymphoma Plasmacytoma CLL Waldenstrom's
What is myeloma?
Malignant proliferation of plasma cells in bone marrow
–> large amount of identical Ig (paraprotein) + free light chains (Bence Jones proteins if in urine)
How is myeloma classified?
By Ig class:
- 2/3 are IgG
- 1/3 are IgA
- rest are IgM or IgD
What happens to the other classes of Ig in myeloma?
Other classes will be low –> immunoparesis
What are the key features of myeloma?
Osteolytic bone lesions --> fractures + bone pain --> HYPERCALCAEMIA Pancytopenia (marrow infiltration) Infection (immunoparesis) Renal disease Hyperviscosity
What is the mechanism of kidney injury in myeloma?
Light chains (BJPs) deposit in kidneys –> tubular obstruction + kidney failure = cast nephropathy