Mae Haruki, Kanzaki Go, Inamura Yumeka, Matsuo Nanae, Honma Shiko, Suzuki Kazuhito, Tsuboi Nobuo, Joh Kensuke, Yano Shingo, Yokoo Takashi
Division of Nephrology and Hypertension, Department of Internal Medicine, The Jikei University School of Medicine, 3-25-8 Nishi-Shimbashi, Minato-Ku, Tokyo, 105-8461, Japan.
Division of Pathology, Department of Internal Medicine, The Jikei University School of Medicine, Minato, Tokyo, Japan.
CEN Case Rep. 2025 Sep 3. doi: 10.1007/s13730-025-01034-w.
A 65-year-old female patient with Sjögren syndrome (SJS) and tubulointerstitial nephritis (TIN) confirmed by kidney biopsy results 7 years previously presented to our department with progressive kidney function deterioration. Laboratory findings revealed increased serum creatinine level accompanied with deterioration of tubular function. Although she already had signs of proximal tubular dysfunction due to TIN from 7 years before, deterioration of the proximal tubule related parameters was particularly prominent. Owing to the substantial increase in the IgG level, monoclonal gammopathy was considered. Subsequent immunoelectrophoresis of the serum and urine revealed the presence of monoclonal IgG-κ. A repeat kidney biopsy revealed crystalline inclusions in the proximal tubules that tested positive for κ light chain. Along with findings from the bone marrow biopsy, this led to the diagnosis of light chain proximal tubulopathy (LCPT) secondary to multiple myeloma. Chemotherapy was initiated promptly which resulted in stabilization of renal function and improvement of tubular function. Vigilant monitoring of the tubular function is essential for patients with SJS. Deterioration of proximal tubule parameters, especially when accompanied by increased IgG levels, should prompt the investigation of monoclonal gammopathy and the consideration of kidney biopsy.
一名65岁女性患者，7年前经肾活检确诊为干燥综合征（SJS）和肾小管间质性肾炎（TIN），现因肾功能进行性恶化前来我院就诊。实验室检查发现血清肌酐水平升高，同时肾小管功能恶化。尽管7年前她就已因TIN出现近端肾小管功能障碍的体征，但近端小管相关参数的恶化尤为突出。由于IgG水平大幅升高，考虑存在单克隆丙种球蛋白病。随后对血清和尿液进行免疫电泳，发现存在单克隆IgG-κ。再次肾活检显示近端小管中有结晶包涵体，κ轻链检测呈阳性。结合骨髓活检结果，最终诊断为继发于多发性骨髓瘤的轻链近端肾小管病（LCPT）。随即迅速开始化疗，肾功能得以稳定，肾小管功能也有所改善。对SJS患者而言，密切监测肾小管功能至关重要。近端小管参数恶化，尤其是伴有IgG水平升高时，应促使医生调查单克隆丙种球蛋白病并考虑进行肾活检。
