A significant decrease in the gamma band on serum protein electrophoresis most likely indicates which condition?

• A. Normal response to active infection
• B. Monoclonal gammopathy
• C. Immunodeficiency disorder
• D. Multiple myeloma

Answer: (C)

A sharp drop in the gamma region on serum protein electrophoresis points to hypogammaglobulinemia, meaning there are too few antibodies circulating due to an immunodeficiency. Since gamma globulins are antibodies, a significant decrease indicates impaired antibody production, which is a hallmark of immunodeficiency disorders and explains increased infection risk.

In contrast, active infections usually boost gamma globulins because they stimulate many B cells to produce antibodies, raising that area on the gel rather than lowering it. Monoclonal gammopathy and multiple myeloma produce a single dominant antibody band (an M-spike) rather than a broad decrease in the gamma region, reflecting overproduction of one clone of immunoglobulin rather than a deficiency.