Which disease is characterized by clonal proliferation of plasma cells producing monoclonal immunoglobulins?

• A. Leukemia
• B. Lymphoma
• C. Multiple myeloma
• D. Waldenström macroglobulinemia

Answer: (C)

The key idea is a malignant, single clone of plasma cells that makes one type of immunoglobulin, called a monoclonal protein or M protein. In multiple myeloma, these clonal plasma cells accumulate in the bone marrow and secrete a uniform immunoglobulin (often IgG or IgA, sometimes just light chains). This monoclonal production is what sets the disease apart from normal polyclonal immunoglobulin production and from other cancers of the blood.

This is why the described disease fits multiple myeloma: the hallmark is clonal plasma cell proliferation with monoclonal immunoglobulin secretion, leading to issues like bone lesions, anemia, kidney problems, and high calcium in many patients. Other options don’t match this pattern as closely—leukemia is a broad white blood cell cancer, lymphoma involves lymphoid tissue proliferation, and Waldenström macroglobulinemia is a lymphoplasmacytic lymphoma that mainly produces IgM and has different clinical implications (hyperviscosity) and cellular origin.