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What is myeloma?
Myeloma is a hematologic malignancy comprising about 1% of all cancers. It consists of an excess of clonally expanded cytogenetically heterogeneous bone marrow-derived plasma cells with two cardinal features: a monoclonal immunoglobulin (the paraprotein or M-protein) and/or associated light chains (LCs; kappa [κ] and lambda [λ]) with bone destruction that usually manifests as osteolytic lesions.
All myeloma derives from a preclinical phase known as monoclonal gammopathy of unknown significance (MGUS). Myeloma is diagnosed when there is clonal expansion of bone marrow plasma cells >10% and any one myeloma-defining event using the CRAB criteria:
- • Hyper c alcemia
- • R enal insufficiency
- • A nemia
- • B one lesion
The most common class of whole immunoglobulin (Ig) is IgG followed by IgA and IgD. In approximately 20% of patients only an associated LC component is detected. It is a disease of the elderly, with the median age of diagnosis being older than 65 years of age.
At diagnosis, there is evidence of kidney damage in nearly half of patients and up to 10% will have severe kidney failure requiring urgent dialysis. Kidney failure is most common in patients with IgD and LC myeloma.
6 Interesting Facts of Myeloma
1. Patients with myeloma are particularly vulnerable to factors that cause volume depletion or sudden reductions in glomerular filtration. This is because these changes reduce tubular flow and increase the exposure of the tubule to high single-nephron light chain (LC) concentrations.
2. Patients with myeloma most frequently present with the signs and symptoms of kidney failure, anemia, or malignant bone pain, typically low back pain unrelieved by rest or simple analgesics.
3. Urinalysis by dipstix preferentially detect albumin and may be negative in the presence of significant quantities of LCs (Bence-Jones proteinuria).
4. Myeloma cast nephropathy is a medical emergency and requires immediate diagnosis and early institution of therapy in order to prevent irreversible kidney failure.
5. Dexamethasone 20 mg bid, which induces apoptosis of plasma cells, can be immediately commenced to rapidly lower the serum LC load.
6. Bortezomib-based chemotherapy regimens are recommended as the optimal management of acute kidney injury and myeloma
