Myeloma multiplex
Myeloma multiplex = multiple myeloma = myeloma
Myeloma is a haematological cancer characterized by clonal proliferation of plasma cells (and their associated antibodies) in the bone marrow. The massive proliferation of immunoglobulins causes systemic dysfunction in many organs, especially the kidneys.
We classify myeloma based on the type of immunoglobulin that is produced, be that IgG (⅔), IgA (⅓) or IgM or D, the latter two being exceptionally rare.
Myeloma is a so-called plasma cell dyscrasia (dyscrasia a = disordered state), and is often associated with osteolytic bone disease, anaemia and renal failure. Incidence is about 5/100,000 with the median age at diagnosis of 72 y.o., the condition has a prevalence for black males.
There is no clear etiology, however there is some genetic role with familial studies showing links, although no single genes have been identified.
So, multiple myeloma cells arise from post germinal (terminally differentiated) B-cells (aka plasma cells). These cells secrete IgG or IgM into the serum and urine, along with impairing normal immunoglobulin production, leading to relative hypogammaglobulinemia and increasing the risk of infection.
There exists a precursor condition to Multiple Myeloma, the so-called monoclonal gammopathy of undetermined significance (MGUS). MGUS is an increase in Ig in the body but with no end organ damage and clonal bone marrow plasma <10%. In contrast, multiple myeloma cannot be diagnosed until clonal bone marrow plasma >10% OR one of the following events occurs:
- Evidence of end organ damage due to
- Hypercalcaemia
- Renal insufficiency
- Anemia
- Bone lesions - one or more
- Any of the following biomarkers of malignancy
- Clonal bone marrow plasma cell percentage >60%
- Involved:uninvolved serum free light-chain ratio >100
Patients most commonly present with lethargy secondary to anaemia and bone pain (most commonly in the back). The bone pain is the result of a build up of plasma cells in the bone marrow that causes osteolysis. MM can also present as a medical emergency secondary to sepsis, hypercalcaemia, hyperviscosity symptoms and/or spinal cord compression due to vertebral lesions.
In all over 50s with back pain do serum protein electrophoresis and ESR. Patients may present with recurrent bacterial infections, hypercalcaemia and/or proteinuria secondary to renal impairment.
The key diagnostic test is the serum and/or urine electrophoresis for detection of the excess Ig. Bone marrow biopsy is also definitive. Imaging to assess bone disease is essential in all patients due to the prevalence of osteolytic lesions.