|Photomicrograph of bone marrow from patient with multiple myeloma.
Click to enlarge image.
Plasma cells from patients with myeloma are usually immature in appearance with centrally located nuclei, distinct nucleoli, and perinuclear vacuolization. There are also often multinucleated plasma cells.
Immunohistochemical analysis can verify monoclonality.
The plasma cells produce monoclonal IgG or IgA that can be detected through a characteristic serum protein electrophoresis pattern. Eighty percent of the patients have a complete monoclonal Ig in the serum and most of them simultaneously produce light chains something that may cause so-called Bence-Jones proteinuria.
Asymptomatic multiple myeloma
In asymptomatic multiple myeloma, the M-component is >30 g/l and/or plasma cells in bone marrow aspirate >10% without organ involvment related to myelomatosis or the presence of any specific biomarkers.
(Symptomatic) Multiple myeloma
In multiple myeloma, there is M-component in serum or urine (without volume requirement), >10% monoclonal plasma cells in bone marrow aspirate or biopsy. In addition, there must be presence of organ injury related to multiple myeloma or any other selected criteria indicating the high risk of symptom development within a short period of time.
Solitary medullary plasmacytoma
In solitary plasmacytoma, there is solitary bone destruction, with or without tumor, consisting of monoclonal plasma cells without other sign of multiple myeloma.
Plasma cell leukemia
Multiple myeloma where >20% of leukocytes in peripheral blood represent plasma cells or >2 x 109/L of the bloodcells are plasma cells.
In about 1% of the multiple myeloma patients, there is no detectable monoclonal Ig. this is called (real) non-secretory myelomatosis. Immunofluorescence or immunohistochemical analysis of the bone marrow will then almost always demonstrate intracellular monoclonal Ig.
Light chain disease
In 20% of multiple myeloma patients, only light chain is produced. These light chains can most often be measured in serum (FLC) and in urine (urinary electrophoresis).This type of myelomatosis is named “light chain disease”.
These light chains are toxic to the kidneys, therefore, many patients with this disease are referred to the hospital because of renal insufficiency. Patients referred to the hospital with renal insufficiency of unknown cause should be evaluated to exclude myelomatosis with measurements of light chains as described above (FLC and U-elfo).
AL - amyloidosis
There is a type of amyloidosis associated with monoclonal plasma cell proliferative disease, AL-amyloidosis. The amyloid forming protein in this amyloid fibrils is larger or smaller N-terminal fragments of monoclonal light chain IG. These proteins are deposited in the tissue and affect organs. In this disease, there is often found a monoclonal component, either by serum protein electrophoresis, urine protein electrophoresis or by free light chains. Clone plasma cells are found in the bone marrow, although the amount may be low. The same plasma cell clone may also cause myelomatosis, and the patients may therefore have both of these conditions at the same time as part of the same disease. This patient group has a somewhat better prognosis than myelomatosis, but the spread is greater. Patients with affection of the heart have a worse prognosis.