Monoclonal gammopathies range from asymptomatic, premalignant monoclonal gammopathy of undetermined significance (MGUS) to life-threatening manifestations such as light chain amyloidosis or fast-progressing multiple myeloma requiring highly aggressive therapy.
Some years ago, the diagnosis of monoclonal gammopathies was based on the finding of an elevated level of a complete immunoglobulin. However, there are a substantial number of monoclonal gammopathies in which no increased expression of intact immunoglobulin molecules is seen, but rather increased levels of either the free light chain (FLC) kappa or lambda, resulting in an abnormally low or high FLC kappa/lambda ratio.