IgM单克隆蛋白血症未定型病（MGUS）患者的一部分会发展出IgM相关疾病（IgM-RD），包括外周神经病、冷球蛋白血症和/或冷凝集素病（CAD）。我们检查了191名IgM MGUS患者（2016 WHO标准）的临床和骨髓病理学结果。克隆性浆细胞在171个病例（24%）中通过免疫组织化学法（IHC）鉴定，而克隆性B细胞在157个病例（27%）中鉴定。其中82例（43%）被诊断为IgMRD，包括外周神经病（n = 67，35%）、冷球蛋白血症（n = 21，11%）和CAD（n = 10，5%）。CAD的病例显示出独特的特征，包括MYD88基因突变缺失（p = 0.048），支持原发性CAD是一种独立的临床病理学疾病的概念。排除CAD后，对其余病例（n = 72）与无IgM-RD病例（n = 109）进行比较，发现IgM-RD在男性中的频率高于女性（p = 0.02），同时与MYD88 L265P有更高的相关性（p = 0.011）。有和没有IgM-RD的病例除了流式细胞仪检测到克隆性B细胞或IHC检测到克隆性浆细胞外，在血清IgM浓度、淋巴结聚集体的存在等方面显示相似的结果。没有观察到有关IgM-RD的总体生存差异。本研究中没有符合2022年国际共识淋巴结肿瘤分类定义的浆细胞型IgM MGUS病例。这些结果表明IgM MGUS患者中IgM-RD很常见。除CAD外，其余IgM-RD病例大多显示与无IgM-RD的IgM MGUS相似的病理学结果。

A subset of patients with IgM monoclonal gammopathy of undetermined significance (MGUS) develop IgM-related disorders (IgM-RD) including peripheral neuropathy, cryoglobulinemia and/or cold agglutinin disease (CAD). We examined the clinical and bone marrow pathologic findings in 191 IgM MGUS patients (2016 WHO criteria). Clonal plasma cells were identified in 41/171 (24%) cases by immunohistochemistry (IHC) and clonal B-cells in 43/157 (27%). IgMRD was identified in 82 (43%) cases, including peripheral neuropathy (n=67, 35%), cryoglobulinemia (n=21, 11%), and CAD (n=10, 5%). Cases of CAD showed distinctive features including lack of MYD88 mutations (p=0.048), supporting the concept of primary CAD as a distinct clinicopathologic disorder. Following exclusion of CAD, comparison of the remaining cases with (n=72) or without (n=109) IgM-RD showed IgM-RD to be more frequent in men than women (p=0.02) and to be more highly associated with MYD88 L265P (p=0.011). Cases with and without IgM-RD otherwise showed similar features including serum IgM concentrations, presence of lymphoid aggregates, clonal B-cells by flow cytometry or clonal plasma cells by IHC. No differences were observed in overall survival between cases with and without IgM-RD. No cases in this series met criteria for plasma cell type IgM MGUS as defined in the 2022 International Consensus Classification of lymphoid neoplasms. These results show IgM-RD to be common in patients with IgM MGUS. While CAD shows distinctive features, the remaining cases of IgM-RD largely show pathologic findings similar to IgM MGUS without IgM-RD.