Thursday, January 8, 2009

Clinical features of Multiple Myeloma

(rouleaux formation on blood film)

Multiple Myeloma is a hematologic malignancy that arises from a single clone of plasma cells producing a monoclonal immunoglobulin (usually IgG or IgA). The plasma cells proliferate in the bone marrow - many of the clinical features and complications of this disease arise from the proliferation of these cells, and the immunoglobulins which are released.

Anemia: Very common. Essentially, the plasma cells proliferate and displace the normal bone marrow. An autoimmune destruction of RBC's can also occur.

Bone Pain: Also very common, and usually secondary to lytic lesions or pathologic fractures. Nerve compression may result from this . There is increased osteoclast and decreased osteoblast activity. A cytokine known as RANKL is likely responsible for the osteoclast activity.

Renal disease: there are many mechanisms for this to occur including deposition of filtered light chains in the glomerulus, acute tubular necrosis from light chain deposition, amyloidosis, hypercalcemia, type II renal tubular acidosis...or Fanconi's syndrome, urate nephropathy, or pyelonephritis.

Recurrent Infection: this is also very common and is likely secondary to hypogammaglobulinemia and impaired plasma cell function. Pneumonia and pyelonephritis are common.

Laboratory examination may reveal anemia. Rouleaux will be frequently seen on blood film secondary to the high burden of protein (immunoglubulins) expelled by the plasma cells. Hypercalcemia and renal failure are also common (here is a link to hypercalcemia in malignancy). Serum protein electrophoresis will often detect a an M Spike - this is the immunoglubulin that is being overproduced by the clonal plasma cells. You can determine which immunoglobulin it is via immunofixation. In about 15% of cases, only a light chain of the immunoglubulin is secreted, and these can be detected in the urine as Bence-Jones proteins via urine protein electrophoresis and immunofixation. Rarely (less than 5% of the time) plasma cells will not secrete immunoglobulins.

Bone marrow biopsy is essential to confirm the diagnosis of multiple myeloma, and by definition would require more than 10% clonal plasma cells.

Unfortunately this disease has a poor prognosis with survival ranging between 2 to 5 years.

Here is a good paper on malignancy related hypercalcemia.
Here is a review for the various treatments of multiple myeloma.

(lytic bone lesions on the skull of a patient with multiple myeloma)

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