Review Question - QID 522

The answer is Monoclonal light chain immunoglobin.

Figure A shows multiple plasma cells suggestive of multiple myeloma. Multiple myeloma is a neoplastic process involving the proliferation of plasma cells. It is often associated with anemia, chronic pain, low-grade fevers, and skeletal lesions that are often "cold" on bone scans. Affected B-cells produce a single, non-functional antibody (ie “monoclonal”, and this can either be the light chain or the heavy chain, most commonly part of an IgG protein) which becomes the predominant antibody (nonfunctional) produced as the disease progresses. Quantitative measurements by urine electrophoresis can be used to diagnose and monitor the disease. Alternatively serum electrophoresis can be used to detect monoclonal heavy chain immunoglobins as monoclonal light chains are preferentially excreted by the kidneys.

Additional findings include: hypercalemia (when osteoclasts are breaking down bone, releasing calcium into the bloodstream), raised serum creatinine due to reduced renal function, which may be due to light chain deposition in the kidney.