Keywords: G-protein-coupled; GPRC5D, G protein-coupled receptor family C group 5-member D; MM, multiple myeloma; R/R, relapsed or refractory; anticancer drugs; bispecific antibody; chemotherapeutic; cytotoxicity; drug effects; immunology; immunotherapy; multiple myeloma; nail diseases; onychomadesis; palmoplantar keratoderma; talquetamab.; targeted therapy.