Teclistamab-Induced Localized Pleural Cavity Cytokine Release Syndrome in a Multiple Myeloma Patient Managed with Intrapleural Dexamethasone Administration.

Teclistamab, a B-cell maturation antigen (BCMA) × CD3 bispecific T-cell engager, has shown significant efficacy in patients with refractory multiple myeloma (MM). However, the clinical characteristics and optimal management strategies for localized cytokine release syndrome (CRS) remain poorly defined compared with systemic CRS. We report the case of a 57-year-old woman with refractory MM who developed both systemic and localized CRS following teclistamab therapy. She initially presented with grade 3 systemic CRS during step-up dosing phase, which partially resolved with intravenous methylprednisolone. However, interleukin-6 remained elevated in pleural effusions but not in serum, indicating localized pleural cavity CRS. Management with pleural fluid drainage combined with intrapleural dexamethasone successfully controlled the localized CRS. At two months, the patient achieved a partial response and continued teclistamab therapy. To our knowledge, this is among the first reported cases of teclistamab-associated localized pleural cavity CRS effectively managed with intrapleural dexamethasone.