Division of Hematology, University of the Philippines - Philippine General Hospital, Manila, Philippines.
Division of Hematology, University of British Columbia, Vancouver, Canada.
Hematology. 2020 Dec;25(1):335-340. doi: 10.1080/16078454.2020.1815130.
: Serum IgG4 is typically measured to investigate for Immunoglobulin G4-related Disease (IgG4-RD), a fibroinflammatory condition associated with polyclonal increase in serum IgG4. However, increased IgG4 can also be monoclonal, and little is known about IgG4 myeloma. : We describe two cases of IgG4 myeloma without clinical, radiologic, or laboratory features of IgG4-related disease. : An 84 year old man presented with anemia and compression fractures and a 77 year old man presented with anemia, hypercalcemia and renal failure. Both had markedly elevated monoclonal serum IgG4, 34 g/L and 48 g/L in the beta region, and increased IgG positive bone marrow plasma cells, 50% and 80%, respectively. Neither had clinical or radiological manifestations of IgG4-related disease (IgG4-RD) such as salivary or lacrimal gland swelling, autoimmune pancreatitis , or retroperitoneal fibrosis. Both cases responded well to standard myeloma therapy. The IgG4 paraprotein caused spuriously elevated beta-2 microglobulin of 45.2 mg/L in case two due to interference with the assay. : These cases illustrate the importance of performing serum protein electrophoresis in tandem with IgG subclasses to distinguish between polyclonal and monoclonal increases in serum IgG4. The lack of typical IgG4-RD features in these two patients suggests that monoclonal elevation in serum IgG4 alone is insufficient to cause the organ damage characteristic of IgG4-RD. Larger studies of IgG myeloma subtypes are warranted to explore whether IgG1, IgG2, IgG3 and IgG4 myeloma differ in natural history and whether the interference with beta-2 microglobulin is specific to IgG4 monoclonal proteins.
血清 IgG4 通常用于检测 IgG4 相关疾病 (IgG4-RD)，这是一种与血清 IgG4 多克隆增加相关的纤维炎性疾病。然而，IgG4 也可以是单克隆的，关于 IgG4 骨髓瘤的了解甚少。
我们描述了两例 IgG4 骨髓瘤病例，这些病例没有 IgG4 相关疾病的临床、影像学或实验室特征。
一位 84 岁的男性患者因贫血和压缩性骨折就诊，另一位 77 岁的男性患者因贫血、高钙血症和肾衰竭就诊。两名患者的血清 IgG4 单克隆均显著升高，β区分别为 34 g/L 和 48 g/L，且 IgG 阳性骨髓浆细胞分别增加了 50%和 80%。两名患者均无 IgG4 相关疾病（IgG4-RD）的临床或影像学表现，如唾液腺或泪腺肿胀、自身免疫性胰腺炎或腹膜后纤维化。两种情况均对标准骨髓瘤治疗反应良好。由于干扰，第二种情况下 IgG4 副蛋白导致β-2 微球蛋白假性升高至 45.2 mg/L。
这些病例说明了在 IgG 亚类与血清蛋白电泳联合使用时，区分 IgG4 多克隆和单克隆增加的重要性。这两名患者缺乏典型的 IgG4-RD 特征表明，单独的血清 IgG4 单克隆升高不足以引起 IgG4-RD 的特征性器官损伤。需要进一步研究 IgG 骨髓瘤亚型，以探讨 IgG1、IgG2、IgG3 和 IgG4 骨髓瘤在自然史方面是否存在差异，以及β-2 微球蛋白的干扰是否特定于 IgG4 单克隆蛋白。
