Abstract：
IgG4-related diseases (IgG-RDs) are a group of fibroinflammatory diseases that affect a variety of tissues, resulting in tumour-like effects and/or organ dysfunction. Monoclonal gammopathies (MGPs) are a group of disorders characterized by clonal proliferation of plasma cells or lymphoid cells resulting in the secretion of a monoclonal immunoglobulin. Cases of MGPs in IgG4-RDs coexisting with plasma cell dyscrasias and lymphoid neoplasms have been reported over the past few years. Therefore, the results of examinations of M protein in IgG4-RD patients should be interpreted with caution. Herein, we report the case of a 58-year-old male with a history of type 2 diabetes who presented with submandibular masses, anosmia, swollen lymph nodes, proteinuria, and renal impairment. Laboratory tests revealed hyperglobulinemia and elevated levels of IgG4 (124 g/L) and serum-free light chains (sFLCs). Serum protein electrophoresis (SPEP) revealed an M spike of 5.6 g/dL, and immunofixation electrophoresis (IPE) revealed biclonal IgG-κ and IgG-λ. The patient underwent bone marrow, lymph node, and kidney biopsy, which ruled out plasma cell disorders and lymphoma. He was finally diagnosed with an IgG4-RD comorbid with diabetic nephropathy. The findings in this case highlight that significant activation of B cells in IgG4-RD patients, especially those with multiorgan involvement can lead to significant hyperglobulinemia and high sFLC and IgG4 levels, which are more pronounced in the setting of renal impairment. Relatively high concentrations of polyclonal IgG4 can give rise to a focal band bridging the β and γ fractions, which may mimic the appearance of a monoclonal band on SPEP and monoclonal gammaglobulinemia in IFE. The patient experienced considerable improvement in his symptoms after rituximab combined with glucocorticoid therapy, and a monoclonal immunoglobulin was not detected.
摘要：
IgG4相关疾病（IgG-RD）是一组影响多种组织的纤维炎症性疾病，导致肿瘤样效应和/或器官功能障碍。单克隆丙种球蛋白病（MGP）是一组疾病，其特征是浆细胞或淋巴细胞的克隆增殖导致单克隆免疫球蛋白的分泌。在过去的几年中，已经报道了IgG4-RD中的MGP与浆细胞发育不良和淋巴样肿瘤共存的病例。因此,IgG4-RD患者的M蛋白检查结果应谨慎解释.在这里，我们报告了一个58岁的男性，有2型糖尿病病史，表现为颌下肿块，嗅觉缺失,淋巴结肿大,蛋白尿,和肾功能损害。实验室测试显示高球蛋白血症和IgG4（124g/L）和无血清轻链（sFLC）水平升高。血清蛋白电泳（SPEP）显示5.6g/dL的M峰值，免疫固定电泳（IPE）显示了双克隆IgG-κ和IgG-λ。病人接受了骨髓,淋巴结,还有肾活检,排除了浆细胞疾病和淋巴瘤。他最终被诊断为IgG4-RD合并糖尿病肾病。在这种情况下的发现强调了IgG4-RD患者中B细胞的显着激活，尤其是多器官受累的患者可导致显著的高球蛋白血症和高sFLC和IgG4水平，在肾功能损害的背景下更明显。相对高浓度的多克隆IgG4可以产生桥接β和γ部分的局域带。这可能模拟SPEP上的单克隆条带和IFE中的单克隆丙种球蛋白血症的出现。利妥昔单抗联合糖皮质激素治疗后，患者的症状有了相当大的改善，并且未检测到单克隆免疫球蛋白.
