A 79-year-old woman has a monoclonal IgG spike in serum protein electrophoresis without signs of multiple myeloma. What is the most likely explanation for this finding?

• A. Chronic hepatic disease
• B. Chronic inflammation
• C. Monoclonal gammopathy of uncertain significance
• D. Multiple myeloma

Answer: (C)

The presence of a monoclonal IgG spike in serum protein electrophoresis can indicate a proliferation of a single clone of plasma cells producing immunoglobulin. In the absence of symptoms or signs of multiple myeloma or related conditions, the most likely explanation for this finding is monoclonal gammopathy of uncertain significance (MGUS).

MGUS is characterized by the presence of a monoclonal protein in the absence of evidence for a hematological malignancy, such as multiple myeloma or lymphoma. This condition is common in elderly patients and generally does not cause any clinical symptoms, which aligns with the description of this 79-year-old woman. In MGUS, the levels of monoclonal protein are typically lower than they would be in multiple myeloma, and there are no associated end-organ damage or myeloma-related symptoms.

Chronic hepatic disease and chronic inflammation can also lead to abnormal protein levels but typically do not result in a monoclonal spike, as these conditions tend to produce polyclonal increases in immunoglobulins. Additionally, multiple myeloma would present with a distinct set of clinical symptoms or complications, such as anemia, bone lesions, or renal impairment, which are not indicated in this scenario.