#00066182

A 57-year-old woman with heavily pre-treated multiple myeloma presented following the first treatment dose of talquetamab. Eight days after the first full dose of talquetamab, the patient complained of a rash and peeling skin on the hands and groin. The patient experienced initial improvement after the initiation of topical steroids, but the condition began to worsen after several days. Skin biopsy revealed psoriasiform dermatitis parakeratosis of the stratum corneum, no epidermal interface changes, and mild perivascular lymphohistiocytic infiltrates in the dermis without eosinophils. The patient was initiated on methylprednisolone 64 mg for 4 days, followed by prednisone 70 mg with a prolonged taper. Although skin rash is a well-known side effect of talquetamab, prompt diagnosis and systemic treatment are necessary to prevent worsening of skin toxicity and secondary complications.