The targeting of GPRC5D on the surface of cells that produce keratin is most likely responsible for the development of the GPRC5D-specific ‘on target/off tumor’ adverse events, including skin-related adverse events (rash, as well as palmar/plantar desquamation [Fig. 3]), nail-related adverse events, and dysgeusia [46,47]. This evidence concerns the gene GPRC5D and neoplasm.