• sFLC analysis may be of use in monitoring some patients with monoclonal cryoglobulinaemia.
  • Monoclonal sFLCs are sometimes associated with heavy chain disease. Hevylite® antibodies do not recognize the solitary, truncated heavy chains produced.
  • The plasma cell proliferations underlying POEMS syndrome are typically small and difficult to detect. sFLC concentrations are usually elevated but less than 20% of patients have abnormal sFLC ratios.

The three disorders described in this chapter can all result from monoclonal plasma cell proliferations; for POEMS syndrome this is exclusively so, while heavy chain disease (HCD) may be a consequence of other B-cell lymphoproliferative disorders. Cryoglobulinaemia may likewise be associated with a lymphoproliferative malignancy but is most usually seen in association with hepatitis C virus (HCV) infections. A feature they share is the production of abnormal immunoglobulins. They have all been investigated using serum free light chain (sFLC) and/or immunoglobulin heavy/light chain (Hevylite, HLC) analysis.