Patient with refractory multiple myeloma developing eosinophilia after lenalidomide treatment and lung cancer 9 months later: case report and review of the literature.

A 78-year-old man was diagnosed as having advanced symptomatic IgG multiple myeloma in June 2008. Melphalan-prednisolone therapy was effective, however, relapse occurred in January 2011 after 21 courses of melphalan-prednisolone therapy. Addition of bortezomib and dexamethasone led to partial remission, but the treatment needed to be discontinued due to autonomic dysfunction. Combined therapy with lenalidomide and dexamethasone was started in May 2012, which resulted in partial remission. The patient had a persistently elevated eosinophil count (2,350/μL) and increased serum IL-6 level. Pleuritis carcinomatosa developed in January 2013. Lenalidomide was discontinued, which was followed by rapid improvement of the eosinophilia. The patient died of respiratory failure in March 2013. There have been only five reported cases of eosinophilia caused by lenalidomide used for the treatment of multiple myeloma. In these cases, lenalidomide has been speculated to activate cytotoxic T cells to control the plasmacytoma. It would be of interest, therefore, that eosinophilia could serve as a new indicator.