A monoclonal protein identified by an anomalous lipaemia index.

We describe a patient being investigated for anaemia where the lipaemia index on a Beckman Coulter DxC800 analyser was markedly elevated and out of keeping with the visual appearance of the serum. Subsequent investigation revealed a monoclonal IgM kappa immunoglobulin with type I cryoglobulin behaviour. The patient was then diagnosed with a non-Hodgkin B-cell lymphoma. We later identified a second patient with a similar anomalous index with an IgM lambda paraprotein, and a known marginal zone splenic lymphoma but were unable to confirm cryoglobulin behaviour prior to treatment. A review of 50 consecutive IgM paraproteins revealed no other anomalous lipaemia indices. We postulate that it is the properties of the paraprotein that determine its cryoglobulin behaviour that also render it susceptible to precipitation in the index diluent, not the fact of it being an IgM paraprotein per se. This appears to be the first reported case of a paraprotein identified following an anomalous lipaemia index.