Approximately 80% of all multiple myeloma (MM) patients produce monoclonal intact immunoglobulins, with 95% of these also producing monoclonal serum free light chains (sFLCs). IgG intact immunoglobulin multiple myeloma (IIMM) accounts for more than half of all MM patients, and IgA IIMM accounts for a further 20% of cases (Table 17.1) . Only around 1 - 2% of patients have IgD IIMM  and monoclonal IgM is present in less than 1% of MM patients  (more commonly found in Waldenström’s macroglobulinaemia, Chapter 32). IgE MM is extremely rare, with fewer than 50 cases reported in the literature . Around 1-2% of MM patients are diagnosed with biclonal gammopathy (Sections 7.7 and 17.2) . In such cases, two monoclonal proteins are identified that can differ in their heavy chains, light chains or both. It has been proposed that the larger (dominant) monoclonal protein is a product of the active MM clone(s), and the smaller (minor) monoclonal protein represents a separate benign MGUS-like clone (Chapter 13) .
Measurements of the monoclonal intact immunoglobulin and sFLC are essential for diagnosis and follow-up of IIMM, and form the basis of response criteria . This chapter reviews intact immunoglobulin and sFLC measurements at diagnosis. The limitations of serum electrophoretic techniques used to quantify monoclonal intact immunoglobulins are discussed, along with heavy chain/light chain immunoglobulin (Hevylite, HLC) assays.
|Type||% of MM patients*|
|κ FLC only||9|
|λ FLC only||7|
Table 17.1. Types of serum monoclonal proteins in 1027 patients with multiple myeloma . *Total does not equal 100% due to rounding.