一名77岁的日本女性,有21年的血清阳性病史,糜烂性类风湿关节炎(RA)和甲氨蝶呤(MTX)治疗10年的病史因不适和轻度意识障碍而入院。实验室数据显示高钙血症,急性肾损伤,正常细胞性贫血,和血小板减少症.当我们首先假设MTX和eldecalcitol的药物诱导毒性时,两组患者均停止治疗,并给予亚叶酸抢救治疗和降钙素.然而,她的病情继续恶化。血清蛋白电泳显示只有一个小的M峰,血清和尿液的免疫电泳显示Bence-Jonesκ(κ)型单克隆蛋白没有免疫球蛋白重链,骨髓检查显示浆细胞增殖。我们诊断她患有Bence-Jonesκ型多发性骨髓瘤(MM),并将她转移到高级医疗机构的血液科。最后,免疫球蛋白(Ig)D-κ型MM的诊断,这种疾病的一种罕见变体,根据血清免疫固定测定。先前的几项研究表明,预先存在的RA是MM的危险因素。尽管与其他亚型相比,IgDMM的特征在于其临床严重程度和不良预后,常被误诊或误认为是轻链型MM,在目前的情况下,因为IgDM蛋白水平低,导致诊断延迟。当不活跃的RA患者出现无法解释的钙升高时,医生必须考虑MM作为鉴别诊断,肾功能衰竭,贫血,和骨病变的症状,应及时了解IgDMM,以建立正确的诊断。
A 77-year-old Japanese woman with a 21-year history of seropositive, erosive rheumatoid arthritis (RA) and a 10-year history of methotrexate (MTX) therapy was admitted with malaise and mild consciousness disturbance. Laboratory data showed hypercalcemia, acute kidney injury, normocytic anaemia, and thrombocytopenia. As we first assumed drug-induced toxicity by MTX and eldecalcitol, both were discontinued and leucovorin rescue therapy and calcitonin were administered. However, her condition continued to worsen. Serum protein electrophoresis showed only a small M-peak, immunoelectrophoresis of both the serum and urine demonstrated Bence-Jones kappa (κ) type monoclonal protein without immunoglobulin heavy chain, and bone marrow examination revealed proliferation of plasma cells. We diagnosed her with Bence-Jones κ type multiple myeloma (MM) and transferred her to the department of haematology of a higher order medical institution. Conclusively, the diagnosis of immunoglobulin (Ig) D-κ type MM, a rare variant of this disorder, was determined in accordance with serum immunofixation. Several previous studies have suggested that pre-existing RA is a risk factor for MM. Although IgD MM is characterised by its clinical severity and poor prognosis compared to other subtypes, it is often misdiagnosed or mistaken as light chain type MM, as in the present case, because of the low level of IgD M-protein, resulting in delayed diagnosis. Physicians must take MM into consideration as a differential diagnosis when inactive RA patients present with inexplicable elevated calcium, renal failure, anaemia, and bone lesion symptoms and should be aware of IgD MM to establish the correct diagnosis promptly.