B35-40 Igg4-related Disease Presenting With Large-vessel Vasculitis: Two Distinct Cases Involving the Aorta and Coronary Arteries

Abstract Rationale IgG4-related disease (IgG4-RD) is a rare fibroinflammatory disorder that can affect virtually any organ system. Vascular involvement, particularly of the aorta or coronary arteries, is exceedingly uncommon and poses diagnostic and therapeutic challenges. Case 1 A 60-year-old woman was diagnosed with IgG4-related disease (IgG4-RD) in 2013 based on a surgical lung biopsy revealing typical histopathological features. Serum IgG4 levels were normal, and no other organ involvement was found. She was observed until 2017, when clinical and radiologic progression with functional decline (TLCO from 63% to 38% predicted) prompted glucocorticoid (GCS) therapy, resulting in partial recovery. In 2024, at age 70, she presented with fever, chest and back pain, elevated CRP (300 mg/L), and acute interstitial nephritis. After antibiotics, partial improvement was noted, but weakness and chest pain persisted. CT revealed an inflammatory periaortic mass involving the thoracic and abdominal aorta with aneurysmal dilatation, and PET-CT showed moderate FDG uptake (SUVmax 3.1). Serum IgG4 was not elevated, but clinical and imaging features were consistent with IgG4-related periaortitis. Combined immunosuppressive therapy (GCS + cyclophosphamide/azathioprine) was introduced, followed by endovascular stent graft implantation in July 2024. Complete clinical and radiological remission was achieved; treatment was completed in October 2025. Case 2 A 55-year-old man with asthma and chronic rhinosinusitis presented with mediastinal lymphadenopathy and coronary wall thickening detected incidentally in July 2025. His history included eosinophilic pericarditis (2017) and lacrimal gland enlargement (2023). Laboratory tests revealed elevated CRP (13.7 mg/L), eosinophilia (0.95 ×10³/μL), IgE 1549 IU/mL, hypergammaglobulinemia (IgG 3121 mg/dL), and markedly increased IgG4 (1890 mg/dL; N 90). Cardiac MRI showed active inflammation of coronary arteries, pericardium, and myocardium with aneurysmal dilatation of the right coronary artery and left main bifurcation. Coronary vasculitis in the setting of IgG4-RD was diagnosed. Immunosuppressive treatment with GCS and cyclophosphamide was initiated, with follow-up MRI planned shortly to assess response. Discussion These cases highlight extremely rare large-vessel involvement in IgG4-RD, affecting both the aorta and coronary arteries. They demonstrate that severe vascular disease may arise even after long-term remission and with normal IgG4 levels, underscoring the limited value of serology alone and the need for continued surveillance. Unexpected coronary inflammation with aneurysms further shows that IgG4-RD should be considered in unexplained vasculitic or inflammatory arterial lesions. These observations expand the vascular spectrum of IgG4-RD and emphasize the importance of advanced imaging, multidisciplinary assessment, and timely immunosuppression to prevent irreversible vascular damage. This abstract is funded by: None