Phenotyping of IgG4-related diseases based on affected organ pattern: A multicenter cohort study using cluster analysis.

Objectives: Immunoglobulin G4-related disease (IgG4-RD) is a systemic, multiorgan disease of unknown etiology. We aimed to classify IgG4-RD by a combination pattern of affected organs and identify the clinical features, including the comorbidities of each subgroup.
Methods: Patients diagnosed with IgG4-RD between April 1996 and June 2018 were enrolled from three institutes. Hierarchical cluster analysis was performed using six frequently affected organs (lacrimal gland and/or orbit, salivary gland, lung, pancreas, kidney, and retroperitone and/or aorta). Clinical features, such as comorbidities and outcomes, were compared between clusters.
Results: In total, 108 patients enrolled in this cohort could be stratified into five distinct subgroups: group 1, lung dominant group; group 2, retroperitoneal fibrosis and/or aortitis dominant group; group 3, salivary glands limited group; group 4, Mikulicz's disease dominant group; and group 5, autoimmune pancreatitis with systemic involvement group. There were significant between-group differences in sex (male dominant in group 1, 2, and 5), history of asthma and allergies on the respiratory tract (most frequent in group 5), and malignancy (most frequent in group 5).
Conclusion: IgG4-RD can be classified into subgroups according to the pattern of affected organs. Group 5 may have frequent complications with allergies and malignancies.