Acute Autoimmune Pancreatitis and Interstitial Nephritis, Due to IgG4 Disease, Following Pfizer-BioNTech COVID-19 Vaccination<br>—IgG4 Disease Following COVID-19 Vaccination

Background: Immunoglobulin G4-related disease (IgG4-RD) is a multi-organ, fibro-inflammatory condition characterized by triad of; 1) lymphoplasmacytic infiltrate, storiform fibrosis, obliterative phlebitis, and increased IgG4+ plasma cells, 2) elevated serum IgG4 levels, and 3) good response to Corticosteroids. Its etiology is uncertain. Case: A 60-year-old man developed persistent acute pancreatitis for 1 month following Pfizer-BioNTech COVID-19 vaccination. Moreover, he had progressive acute renal failure. Computerized tomography of abdomen and pelvis did not show abnormality, especially in the peripancreatic region. Moreover, endoscopic ultrasonography did not show pancreatic lesions. His kidney biopsy showed acute interstitial nephritis with a heavy IgG4-plasma cell infiltrate. Autoimmune workup was negative except for high IgG4 at 1963 g/L (N: 0.039 - 0.864) with IgG4/IgG ratio at 0.16. Hence, diagnosis of IgG4-RD was established. He was treated with Prednisone 1 mg/kg for 1 month which was tapered till discontinuation by 3rd month. His clinical picture, biochemical indices and IgG4 level returned to normal by 2nd week. Such improvement persisted up to 2 years. Conclusion: Overt IgG4 disease with acute pancreatitis and interstitial nephritis can be triggered by COVID-19 vaccination that is amenable to Corticosteroids. It confirms the autoimmune etiology of IgG4-RD triggered by COVID-19 vaccine in a genetically predisposed patient.