CAR-T细胞免疫疗法的发展显着提高了治疗多发性骨髓瘤的疗效。目前，包括 BCMA、CS1、CD38、FcRH5 和 GPRC5D 在内的多种靶点正在研究中。尽管取得了这些重大进展，但抗原逃逸、CAR-T 细胞持久性有限以及肿瘤微环境的复杂性等挑战仍然存在，导致治疗后复发。我们报告了一名复发性难治性多发性骨髓瘤 (RRMM) 患者的病例）经过多轮放疗和化疗后，下肢肌肉中出现了明显的髓外浆细胞瘤。患者接受了针对BCMA和CS1的CAR-T细胞免疫治疗；然而，尽管接受了治疗，肿瘤仍在进展。随后进行了髓外浆细胞瘤的手术切除。通过将肿瘤组织与邻近组织进行比较，发现肿瘤组织中 MYBL2 表达增加，这可能是双靶向 CAR-T 细胞治疗后髓外复发缺乏改善的原因。 在复发难治性多发性骨髓瘤患者中对于接受多周期化疗和放疗的患者，针对 BCMA 和 CS1 的双靶向 CAR-T 细胞治疗未能有效控制髓外复发。多发性骨髓瘤中 MYBL2 表达升高与预后较差相关。版权所有 © 2024 Shi、Wu、Yao、Du 和 Du。

The development of CAR-T-cell immunotherapy has notably elevated the efficacy of treating multiple myeloma. Currently, a variety of targets, including BCMA, CS1, CD38, FcRH5, and GPRC5D, are being investigated. Despite these significant advancements, challenges such as antigen escape, limited persistence of CAR-T cells, and the intricate nature of the tumor microenvironment persist, leading to relapses following treatment.We report the case of a patient with recurrent and refractory multiple myeloma (RRMM) who developed a substantial extramedullary plasmacytoma in the muscles of the lower limb following multiple rounds of radiotherapy and chemotherapy. The patient underwent CAR-T-cell immunotherapy targeting BCMA and CS1; however, the tumor progressed despite treatment. Surgical resection of the extramedullary plasmacytoma was subsequently performed. Upon comparison of the tumor tissue with the adjacent tissue, increased expression of MYBL2 was noted in the tumor tissue, potentially contributing to the lack of improvement in extramedullary relapse after dual-targeted CAR-T cell therapy.In patients with recurrent and refractory multiple myeloma who underwent multiple cycles of chemotherapy and radiotherapy, dual-targeted CAR-T cell therapy aimed at BCMA and CS1 failed to effectively manage extramedullary relapse. Elevated expression of MYBL2 in multiple myeloma correlates with a poorer prognosis.Copyright © 2024 Shi, Wu, Yao, Du and Du.