What immunoglobulin concentration is excessively increased in patients with Waldenström macroglobulinemia?

In patients with Waldenström macroglobulinemia, there is a significant increase in the concentration of immunoglobulin M (IgM). This condition is characterized by the overproduction of IgM antibodies due to malignant proliferation of B lymphocytes. The elevated levels of IgM can lead to hyperviscosity syndrome, where the blood becomes thicker, potentially causing complications such as reduced blood flow and increased risk of clotting.

In Waldenström macroglobulinemia, the monoclonal IgM can be detected in the serum of affected patients, often leading to symptoms related to the hyperviscous state it creates. This distinguishes Waldenström macroglobulinemia from other conditions, highlighting the specific role of IgM in this hematologic malignancy.