Clinical features, anti-neutrophil cytoplasmic antibody (ANCA) status, and human leucocyte antigen (HLA) phenotypes of patients diagnosed with both rheumatoid arthritis and granulomatosis with polyangiitis: a case series of six patients with predomin

OBJECTIVE: To describe the clinical features of six patients diagnosed with both rheumatoid arthritis (RA) and granulomatosis with polyangiitis (GPA), as well as their anti-neutrophil cytoplasmic antibody (ANCA) status and human leucocyte antigen (HLA) phenotypes. METHOD: Patients diagnosed with both RA and GPA were identified among people followed at our department for ANCA-associated vasculitis. Genomic HLA typing was performed using routine methods. RESULTS: We identified six patients diagnosed with both RA and GPA. All patients were women, five were myeloperoxidase (MPO)-ANCA positive, one was proteinase 3 (PR3)-ANCA positive, five had erosive joint disease, and all patients were immunoglobulin M-rheumatoid factor and/or anti-cyclic citrullinated peptide antibody positive. Five had localized GPA, one had systemic GPA, four had subglottic stenosis, and three had saddle nose deformity. The median time between the two diagnoses was 13 (range 7-17) years. Four patients had RA before GPA, while two had GPA before RA. The MPO-ANCA-positive patients all had an HLA-DR4/DQ8/DPB1*04:01 phenotype. CONCLUSION: In this case series of patients diagnosed with both RA and GPA, a long latency period between the two diagnoses was observed in all cases. All patients were women, the majority had erosive arthritis, and many patients were affected by saddle nose deformity and/or subglottic stenosis. MPO-ANCA was present in the majority of patients, which has not been described before. All patients were HLA-DR4/DQ8/DPB1*04:01 positive. These findings may contribute to our understanding of the underlying pathogenesis and the clinical recognition of this rare disease overlap.