Performance of the 2019 American College of Rheumatology/European League Against Rheumatism Classification Criteria for IgG4-Related Disease in a Latin American Cohort.

BACKGROUND/OBJECTIVE: The 2019 American College of Rheumatology/European League Against Rheumatism Classification Criteria (2019 AECC) for IgG4-related disease (IgG4-RD) is considered a significant advancement in the study of this condition. Most studies evaluating their performance have focused on White and Asian patients, leaving a knowledge gap regarding Latin American populations. Therefore, this study aimed to assess the performance of the 2019 AECC for IgG4-RD in a cohort of Latin American patients. METHODS: A multicenter medical records review study was conducted, involving centers from Argentina, Chile, Mexico, Peru, and Uruguay. Data on IgG4-RD patients and mimicker conditions were collected through a standardized online form. The criterion standard for diagnosing IgG4-RD was based on the fulfillment of the Comprehensive Diagnostic Criteria for IgG4-RD and/or the Consensus Statement on Pathology. The 2019 AECC was retrospectively applied. RESULTS: We included 300 patients, with 180 (60%) having IgG4-RD and 120 (40%) having mimicker conditions. The 2019 AECC had a sensitivity of 66.7% and a specificity of 100%. Sensitivity increased to 73.3% when disease-specific autoantibody items were removed, without affecting specificity. The true-positive cases had more involved organs, a higher availability of biopsy results, and were more likely to belong to the Mikulicz/systemic and proliferative phenotypes. CONCLUSIONS: The use of the 2019 AECC for IgG4-RD in a Latin American population confirms its high specificity in excluding those without the disease. The presence of concomitant autoimmune diseases and clinically nonsignificant disease-specific autoantibodies excludes a significant number of patients from fulfilling the criteria.

Immunoglobulin G4-Associated Rosai-Dorfman Disease: Report of 3 Cases.

Rosai-Dorfman disease is characterized by dilated lymph node sinuses filled with lymphocytes, plasma cells, and histiocytes. Many of these histiocytes classically exhibit emperipolesis of lymphocytes and plasma cells. Abundant immunoglobulin G4+ plasma cells occur in some cases, and a potential relationship with immunoglobulin G4-related disease has been suggested. Here, we report 3 cases of immunoglobulin G4-associated Rosai-Dorfman disease. Immunoglobulin G4-related disease was suspected based on immunoglobulin G4+ plasma cell infiltration, but the final diagnosis was immunoglobulin G4-associated Rosai-Dorfman disease. At present, the evidence does not support a link between immunoglobulin G4-associated Rosai-Dorfman disease and immunoglobulin G4-related disease, and one condition should not be considered part of the spectrum of the other. We believe it is of paramount importance to increase the awareness of immunoglobulin G4-associated Rosai-Dorfman disease for pathologists who interpret the biopsies and clinicians who integrate the diagnosis and treat such patients to not overdiagnose immunoglobulin G4-related disease.

Relapsing polychondritis or relapsing polychondritis-like symptoms associated with IgG4-RD. Case reports and review of the literature.

Relapsing polychondritis (RP) is a rare systemic disorder characterised by recurrent, widespread chondritis of the auricular, nasal, and tracheal cartilages. Immunoglobulin G4-related disease (IgG4-RD) is a systemic immune-mediated disease characterised by the infiltration of IgG4-bearing plasma cells into systemic organs. However, 25-35% of patients with RP have a concurrent autoimmune disease. The coexistence of RP and IgG4 is rare considering that, to the best of our knowledge, there are only four previous reports of RP or RP-like symptoms associated with IgG4-RD. We herein report two cases which could be RP or RP-like symptoms associated with IgG4-RD.