CRBN and plasma cell myeloma: Lenalidomide is an immunomodulatory drug that is recommended and widely used as part of induction therapy and maintenance for multiple myeloma.1-4 Lenalidomide acts via cereblon and induces protein degradation of Ikaros and Ailos eventually leading to myeloma cell death.5, 6 Lenalidomide maintenance is associated with a significantly improved progression-free and overall survival as shown in several clinical trials and a meta-analysis.7-12 Most patients tolerate lenalidomide well; however, fatigue and diarrhea are common side effects in the maintenance phase.