Which monoclonal gammopathy is characterized by IgM production?

Waldenstrom's macroglobulinemia is characterized by the production of IgM antibodies. This condition is classified as a lymphoplasmacytic lymphoma, which primarily involves the proliferation of B-cells that produce high levels of the IgM immunoglobulin. Patients with Waldenstrom's macroglobulinemia often present with symptoms related to hyperviscosity, such as blurred vision, headaches, and bleeding tendencies, due to the excessively increased levels of this immunoglobulin.

In contrast, other conditions listed have different specificities for immunoglobulin production. Multiple myeloma typically involves the overproduction of IgG or IgA, whereas monoclonal gammopathy of undetermined significance may involve various immunoglobulins but does not specifically associate with a single type like IgM in Waldenstrom's. Primary amyloidosis, while it can be associated with multiple myeloma, is primarily characterized by the deposition of amyloid proteins, rather than the monoclonal gammopathy itself. Hence, the defining characteristic of IgM production makes Waldenstrom's macroglobulinemia the correct choice.