Dermatologic Disorders in 118 Patients with Autoimmune (Immunoglobulin G4-Related) Pancreatitis: A Retrospective Cohort Analysis

Background: Autoimmune pancreatitis is the prototypical manifestation of immunoglobulin G4-related disease, a fibroinflammatory syndrome that can affect virtually any organ. Rarely, skin involvement has been reported in immunoglobulin G4-related disease. Isolated case reports have described other distinct associated dermatoses. Objective: Our objective was to determine the frequency and nature of dermatologic manifestations of immunoglobulin G4-related disease in patients with autoimmune pancreatitis. Methods: Retrospective analysis of dermatologic conditions of patients with autoimmune pancreatitis. Results: Among the 118 identified patients, 31 (26.3 %) had a dermatologic diagnosis [mean (standard deviation; SD) follow-up 5.9 (4.6) years]. Two patients (1.7 %) had necrobiotic xanthogranuloma; three (2.5 %) had another xanthomatous or xanthogranulomatous process. One patient (0.8 %) had pemphigus erythematosus. No patient had immunoglobulin G4-related skin disease. Conclusion: Skin involvement in immunoglobulin G4-related disease appears to be rare. A disproportionately high number of patients had xanthomatous or xanthogranulomatous processes, including necrobiotic xanthogranuloma. It remains unclear whether the association between immunoglobulin G4-related disease and necrobiotic xanthogranuloma or other xantho(granulo)matous processes represents shared pathophysiology, a mutual underlying driver, or coincidence, though the results of this study cast doubt on the latter. Although pemphigus was not reported in immunoglobulin G4-related disease previously, the prominent role of the immunoglobulin G4 subclass in each condition makes this association intriguing.