Plasma cell disorders are monoclonal neoplasms: their cells all descend from the same progenitor cell, which belongs to the late B-cell lineage, so they form a single clone. Plasma cells are the late B cells that produce immunoglobulins (antibodies). Normally, the production of immunoglobulins is controlled by the exposure of plasma cells to antigen; in the plasma cell disorders, and especially in the neoplasms, this control is lost, and a single clone over-produces one immunoglobulin. Because this changes the gamma region of the electrophoresis, the band of the blood protein pattern where immunoglobulins run, these conditions are also known as monoclonal gammopathies.
The group is usually described as multiple myeloma (MM), Waldenström macroglobulinemia, primary amyloidosis (AL amyloidosis) and the heavy chain diseases. One feature organises the whole group: there is a chronological evolution from MGUS (monoclonal gammopathy of undetermined significance), to smoldering myeloma, to active myeloma, which can finally lead to the formation of secondary plasma cell leukemia.
Choose a route through the topic
The laboratory finding
- Immunoglobulins and the monoclonal M protein explains the isotype, allotype and idiotype categories of immunoglobulins, how electrophoresis and immunofixation detect and characterise a monoclonal protein, why an M spike alone does not prove a plasma cell disorder, and the slight excess of light chains that plasma cells secrete and the kidney clears.
Multiple myeloma
- Multiple myeloma: definition, epidemiology and genetics opens the myeloma notes with the definition, the origin of the myeloma cell, the age, sex and ethnic pattern of the incidence, and the cytogenetic abnormalities found in the disease.
- Pathogenesis and clinical features of multiple myeloma follows how the cells attach to the marrow and what the tumour and the host response do to the bones, blood, kidneys and nerves.
- Diagnosis of multiple myeloma works through the three components of the diagnosis, the bone marrow studies, the laboratory tests, the blood smear finding and the imaging strategy.
- MGUS, smoldering myeloma and the differential diagnosis of multiple myeloma gives the criteria that separate the precursor states from active myeloma, the SLiM-CRAB myeloma defining events, and what the rates of progression mean for follow-up.
- Prognosis and treatment of multiple myeloma covers β2-microglobulin and the ISS stages, then who is treated, high-dose chemotherapy with autologous stem cell transplantation, radiotherapy, bisphosphonates, supportive care and the newer immunotherapies.
Related clonal disorders
- AL amyloidosis covers the deposition of light-chain material in tissues, how it is demonstrated, and how it differs from myeloma.
- Waldenström macroglobulinemia explains this IgM-secreting monoclonal gammopathy of incompletely matured lymphoid cells, which is a lymphoma rather than a plasma cell dyscrasia.
- Heavy chain diseases explains the rare clonal disorders that make an incomplete heavy chain without a light chain, and how the alpha form involves the small bowel.
Start with the immunoglobulins note if the laboratory terms are new: the M protein it explains is the finding the rest of the topic returns to.