一名 69 岁男性因腰痛就诊，被诊断患有多发性骨髓瘤（IgD-λ 型，R-ISS II 期），腰椎和骶骨出现骨质破坏性病变。染色体分析显示 t (8;14)(q24;q32) 和 t (11;14)(q13;q32)。达雷妥尤单抗、来那度胺和地塞米松治疗产生了部分缓解，但疾病复发，t (11;14) 拷贝数增加，1q21 区域异常扩增。患者因巨细胞病毒肠炎接受治疗，因突发腹痛入院。通过 CT 扫描诊断胃肠穿孔，显示小肠中有游离空气和壁增厚。进行了紧急手术，穿孔区域的肿瘤免疫染色 CCND1 阳性，但 MYC 阴性。手术后患者全身状况未见改善，最终死亡。病理尸检显示除小肠外多个器官均有髓外浸润。髓外浸润被认为是由克隆进化引起的，需要进一步研究以阐明其发病机制并为高危患者建立有效的治疗策略。

A 69-year-old man presented with lumbago and was diagnosed with multiple myeloma (IgD-λ type, R-ISS stage II) with bone-destructive lesions in the lumbar spine and sacrum. Chromosome analysis showed t (8;14)(q24;q32) and t (11;14)(q13;q32). Treatment with daratumumab, lenalidomide, and dexamethasone resulted in partial response, but the disease relapsed, with a copy number increase in t (11;14) and abnormal amplification of the 1q21 region. The patient was treated for CMV enteritis, and was admitted to the hospital due to sudden abdominal pain. Gastrointestinal perforation was diagnosed by CT scan showing free air and wall thickening in the small intestine. Emergency surgery was performed, and the tumors in the perforated area were positive for CCND1 but negative for MYC on immunostaining. The patient's general condition did not improve after the surgery and he died. Pathological autopsy revealed extramedullary infiltration of multiple organs in addition to the small intestine. Extramedullary infiltration is thought to be caused by clonal evolution, and further research is warranted to clarify its pathogenesis and establish effective therapeutic strategies in high-risk patients.