7- Plasma Cell Dyscrasias Flashcards
Define plasma cell
A terminally differentiated B cell whose function is antibody secretion
Decribe the histological appearance of plasma cells
Large nucleus + “clock face” chromatin
What are some possible REACTIVE causes of plasma cell pathology?
- chronic infections (H pylori gastritis, osteomyelitis, endometritis, HIV)
- autoimmune processes (lupus, hepatitis)
What are some possible NEOPLASTIC causes of plasma cell pathology?
- monoclonal gammopathy of undetermined significance
- multiple myeloma
- plasmacytoma (extramedullary or solitary of bone)
- lymphoplasmacytic lymphoma
- amyloidosis
How can we differentiate a reactive versus neoplastic proliferation?
These things indicate neoplasm:
- monoclonal antibodies in serum/urine
- light chain restriction in cell cytoplasm (kappa v lambda) by flow cytometry or IHC
- immunophenotypic aberrancey/abnormality (e.g. CD56, normally on NK cells, expressed on plasma cells in neoplasms)
What is an M protein?
Monoclonal antibodies:
- in serum= intact Ig and/or free light chains
- in urine=
- antibodies may be filtered when kidney damage
- free light chains may pass through glomerulus
- identify with electrophoresis and sensitivie immunoassays
What are bence jones proteins?
Free light chains
What is monoclonal gammopathy?
- presence of an M protein
- may be present in…
- plasma cell disorders
- B cell lymphomas
- RARELY in reactive states
What tests identify monoclonal gammopathy? When do you order them?
- Serum/urine electrophoresis and immunofixation
- Order SPEP/UPEP when myeloma/lymphoma are in the differential diagnosis and for these work-ups:
- neuropathy
- anemia (in older patients)
- osteolytic bone lesions/pathologic fractures
- unexplained renal faliure
- hypercalcemia
What is MGUS?
- monoclonal gammopathy of undetermined significance
- “benign” asymptomatic plasma cell proliferation, but precursor lesion for malignant transformation
- most common form of monoglonal gammopathy
- diagnostic criteria:
- < 3 g/dL serum M protein
- < 10% clonal plasma cells in BM
- no myeloma-related end organ damage
- multiple forms (depending on M protein type)
What is multiple myeloma?
- most common plasma cell neoplasm
- higher incidence in males and african americans
- malignant
- diagnostic criteria:
- > 10% clonal marrow plasma cells OR biopsy proven bone/extramedullary plasmacytoma
- end organ damage (hypercalcemia, renal insufficiency, anemia, bone disease)
Describe bone related end organ damage in myeloma
Lytic bone lesions:
- bone pain
- pathologic fractures
- most common sites= vertebrae, ribs, skull
- ostepenia
Describe hypercalcemia in myeloma
- secondary to bone resorption
- signs/symptoms:
- weakness/lethargy -> coma
- polyuria, stones, renal failure
- constipation, abdominal pain
- depression
- arrythmias
Describe kidney related end organ damage in myeloma
- renal insufficiency in 50% of patients
- bence jones (light chain) proteinuria
- direct nephrotoxicity
- formation of tubular casts (obstruction and inflammation)
- amyloidosis
- light chain glomerulopathy
Describe anemia in myeloma
- may be associated with rouleaux (RBCs clumping together in a line)
- secondary to marrow replacement by plasma cells and/or renal disease
What is plasmacytoma? How is it treated?
- localized growth of monoclonal plasma cells
- may be seen in multiple myeloma or as distinct entity
- when seen as distinct entity:
- no or minimal clonal plasma cells in BM
- +/- M protein
- usually treated with radiation
- 80% of extramedullary plasmacytomas occur in the upper respiratory tract
