Localization of mutations within the CRBN gene.CRBN mutations were found in 6 patients. All mutations found in our cohort occurred at critical sites, and they had the potential to impact CRBN-IMiD interactions by truncating, affecting splicing, or being located within the IMiD-binding site of CRBN. Each mutation is described at the corresponding site of the CRBN protein. CRBN, cereblon; LON, long undivided filaments upon ultraviolet irradiation (homo-oligomeric ATP-dependent protease domain).