Immunoglobulin G4 Related-Disease: A Rare Presentation With Secondary Hypereosinophilic Syndrome and Eosinophilic Ascites.

Immunoglobulin G4 related-disease (IgG4-RD) is a multisystemic immune-mediated fibroinflammatory disease, with a strong predilection for salivary and lacrimal glands, pancreas, biliary tree, lungs, kidneys, aorta, and retroperitoneum. In the case of pancreatic involvement, it manifests as autoimmune pancreatitis. Patients with IgG4-RD usually have mild to moderate eosinophilia in the peripheral blood, however, they may present a secondary hypereosinophilic syndrome (HES). Although there are cases described with severe eosinophilia (> 5,000/µL), the 2019 American College of Rheumatology/European League Against Rheumatism classification criteria for IgG4-RD considers peripheral eosinophilia above 3,000/µL as an exclusion criterion, although stating that assessment for the presence of exclusion criteria should be individualized depending on a patient's clinical scenario. Here, we describe the clinical case of a 30-year-old woman who presented with chronic diarrhea and abdominal pain. The diagnostic workup revealed eosinophilic ascites, severe peripheral blood eosinophilia (> 5,000/µL), IgG4 elevation (> 2 × upper normal limit), and also diffuse swelling in the body and pancreatic tail (computed tomography (CT) scan). There was a prompt response to corticosteroid therapy with clinical resolution and continued remission under therapy. The patient was diagnosed with IgG4-RD with secondary HES, explaining the gastrointestinal tract and peritoneum damage in the form of enterocolitis and ascites. Exclusion of alternative diagnosis was made.