Immunoglobulin G4-Related Disease: A Case of Autoimmune Pancreatitis With Pulmonary Tuberculosis as Proposed Catalyst

Abstract

Immunoglobulin G4-related disease (IgG4-RD) is an immune-mediated condition that often affects multiple organ systems and may present as lymphadenopathy, autoimmune pancreatitis (AIP), salivary gland disease, orbital disease, IgG4-related sclerosing cholangitis, thyroid disease, and/or retroperitoneal fibrosis. 60-90% of patients with IgG4-RD have multisystem involvement. The condition is composed of several disorders that share similar pathologic, serologic, and clinical features. All manifestations share characteristics such as tumor-like swelling of involved organs, a lymphoplasmacytic infiltrate enriched in IgG4(+) plasma cells, and fibrosis with a “storiform” pattern. Elevated serum IgG4 levels are found in 60-70% of patients. Although the exact pathogenesis for IgG4-RD is unclear, it is speculated that IgG4 antibodies respond in a down-regulatory pattern secondary to another primary process. A 59 year old male patient with a past medical history of diabetes mellitus and hypertension presented with the complaint of left upper quadrant abdominal pain without radiation, nausea, vomiting, or jaundice. Physical exam was remarkable only for epigastric pain with palpation. Chest radiograph showed a cavitary lesion in the right apex with chest CT confirming presence of nodules. Lab data showed positive quantiferon gold, elevated lipase, amylase and IgG4. Abdominal MRI showed “sausage” configuration of the pancreas and findings suggestive of IgG4 related cholangitis. The patient's condition improved after initiating therapy with Prednisolone and Isoniazid. This patient's case illustrates AIP in association with an asymptomatic and incidental finding of pulmonary tuberculosis in a patient with no identifiable risk factors. Genetic, immunologic, and molecular mimicry associations with AIP have been hypothesized, however an exact etiology of AIP is still quite ambiguous. Infectious agents play an important role in the development of autoimmune disease in general, with H. pylori recently hypothesized to induce AIP via molecular mimicry. Guernari et al proposed that in genetically predisposed individuals, human and microbial antigens can be a trigger for the onset of AIP with the host immune response targeting human carbonic anyhydrase II. In a literature review, Kawano et al, Imai et al, and Salahuddin et al reported cases of various IgG4 related diseases with an association to tuberculosis. Although many autoimmune triggers exist for AIP, this patient showed a high index of suspicion that M. tuberculosis is the suspected catalyst for the AIP, leading to an autoimmune response versus humoral immunity reaction causing an acute attack on this patient's pancreas supported by elevated IgG4 levels.