Extramedullary relapse of multiple myeloma associated with a shift in secretion from intact immunoglobulin to light chains.

Biological therapies in multiple myeloma have heralded a new and exciting era for treatment to combat this disease. However the evolutionary pressures that these drugs place on the microenvironment has resulted in a change in the biological behaviour of this malignancy and novel manifestations of relapsed disease. This is illustrated in our series of three patients showing fulminant relapse of disease with plasmablastic features, an extramedullary predilection and a shift in secretion from intact immunoglobulin to free light chains only.