Barw Barw Medical Journal 2960-1959 2025 09 20 Emerging Evidence of IgG4-Related Disease in Pericarditis: A Systematic Review 45 65 10.58742/bmj.vi.204 eng Dilan Hikmat Department of Internal Medicine, University of Michigan, Sparrow Hospital, Lansing, Michigan, USA. dilan.sarmad.hiwa@gmail.com Rohan Kumar Department of Internal Medicine, University of Michigan, Sparrow Hospital, Lansing, Michigan, USA. Rohan.Kumar@gmail.com Ghasaq Saleh Department of Internal Medicine, Michigan State University, Sparrow Hospital, Lansing, Michigan, USA. Ghasaq.Saleh@gmail.com Karam Ghazal-Aswad Department of Internal Medicine, University of Michigan, Sparrow Hospital, Lansing, Michigan, USA. Karam.Aswad@gmail.com Mohammad Almasri Department of Internal Medicine, Michigan State University, Sparrow Hospital, Lansing, Michigan, USA. Mohammad.Almasri@gmail.com Mohammed Alaa Raslan Department of Internal Medicine, University of Michigan, Sparrow Hospital, Lansing, Michigan, USA. Mohammed.Raslan@gmail.com Akhil Gaderaju Department of Internal Medicine, Michigan State University, Sparrow Hospital, Lansing, Michigan, USA. Akhil.Gaderaju@gmail.com Adolfo Martinez Department of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota, USA. Adolfo.Martinez@gmail.com Saman Al Barznji Department of Internal Medicine, Michigan State University, Mclaren Oakland, Pontiac, Michigan, USA. saman.barznji@gmail.com Maitri Shah Department of Internal Medicine, Michigan State University, Sparrow Hospital, Lansing, Michigan, USA. Maitri.Shah@gmail.com 2025 07 20 Introduction Immunoglobulin G4-related disease (IgG4-RD) is a recently identified immune-mediated condition that is debilitating and often overlooked. While IgG4-RD has been reported in several organs, this study reviews cases where IgG4-RD caused pericarditis. Methods A systematic search was conducted from inception until March 1, 2025. All age groups and both sexes with confirmed pericarditis were included, along with the following inclusion criteria: 1) Patients with pericardial biopsy showing IgG4/IgG ratio of >40%. 2) Patients with pericardial biopsy revealing IgG4/HPF of >10. 3) Patients who had confirmed IgG4-RD from other organ biopsies through IgG4 staining, or diagnostic imaging suggestive of IgG4-RD, or pericardial biopsy with classic IgG4-RD histopathologic patterns, with elevated serum IgG4 levels, provided no other diagnosis was more likely. Results A total of 50 patients were included, with a mean age of 64.86±15.79 years. There were 36 (72%) males. The most common presenting symptom was dyspnea in 27 (54%) patients. Different pericardial involvements were reported, including pericardial thickening 37 (74%), constrictive pericarditis 28 (56%), pericardial effusion 23 (46%), pericardial calcification 6 (12%), and pericardial nodule 5 (10%). In 28 (56%) patients, only the pericardium was affected. In addition to the pericardium, eight (16%) patients had one other organ affected, and 11 (22%) patients had two additional organs affected. Two (4.5%) cases ended in demise. Conclusion Although rare, IgG4-RD can cause pericarditis, leading to pericardial thickening, effusion, constrictive pericarditis, or the formation of pericardial nodules. Treatment with corticosteroids or pericardiectomy has been associated with favorable outcomes.