Immunoglobulin G4(IgG4)相关疾病 (IgG4-RD) 是一种免疫介导的纤维硬化性疾病，其肿块样病变被IgG4阳性浆细胞浸润。最初被描述为自身免疫性胰腺炎，现在认为IgG4-RD是一种独立实体，并被发现影响身体的几乎任何器官。常见的胰腺外位点包括胆道树、唾液腺、眶周组织、肺、肾、淋巴结、主动脉、腹膜后和甲状腺。诊断依赖于组织病理学、血清学和放射学特征，可能具有挑战性，因为IgG4-RD经常模拟恶性肿瘤、感染性病程或其他免疫介导条件。如果未经治疗，患者可能出现因质量效应导致附近结构的压迫迹象或器官衰竭。该临床过程复杂，涉及单个或多个器官以及病变的间歇性或同步性发生。IgG4-RD对类固醇治疗、疾病改变抗风湿药和B细胞去除生物制剂有良好的反应；及时诊断对于避免治疗延迟和不必要的药物或手术干预是重要的。虽然影像特征可能对于IgG4-RD不具有特异性，但是使用荧光18-脱氧葡萄糖PET/CT的全身功能性成像是定位胰腺外位点进行活检、监测治疗反应和证明疾病复发的有用的辅助检查。作者描述了IgG4-RD在胰腺内外位点的涉及，并利用多模态方法强调了功能性成像评估，以帮助区分IgG4-RD和其模仿者的成像特征和模式。©RSNA, 2023本文的补充材料中提供了测验问题和RSNA年会的幻灯片演示。

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is an immune-mediated fibrosclerosing disease with tumefactive lesions infiltrated by IgG4-positive plasma cells. Initially described as autoimmune pancreatitis, IgG4-RD is now recognized as a discrete entity and is found to affect virtually any organ in the body. Common extrapancreatic sites include the biliary tree, salivary glands, periorbital tissue, lungs, kidneys, lymph nodes, aorta, retroperitoneum, and thyroid gland. Diagnosis-which relies on histopathologic, serologic, and radiologic features-can be challenging with the disease underdiagnosed, as IgG4-RD often mimics malignancy, infectious processes, or other immune-mediated conditions. Patients may present with signs of compression of nearby structures due to mass effect or with organ failure when the disease is left untreated. The clinical course is complex, with single- or multiorgan involvement and metachronous or synchronous occurrence of lesions. IgG4-RD responds well to glucocorticoid therapy, disease-modifying antirheumatic drugs, and B-cell-depleting biologic agents; prompt diagnosis is important to avoid delay in treatment and unnecessary pharmacologic or surgical intervention. While imaging features may not be specific for IgG4-RD, functional whole-body imaging with fluorine 18-fluorodeoxyglucose PET/CT is a useful adjunct for localizing extrapancreatic sites for biopsy, monitoring therapeutic response, and demonstrating disease relapse. The authors describe the pancreatic and extrapancreatic sites of involvement in IgG4-RD, with imaging features and patterns to aid in distinguishing IgG4-RD from its mimics through a multimodality approach with emphasis on functional imaging evaluation. ©RSNA, 2023 Quiz questions in the supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.