The Co-existence of Rheumatoid Arthritis and Granulomatosis With Polyangiitis: Two Cases and Review of the Literature.

Granulomatosis with polyangiitis (GPA) and rheumatoid arthritis (RA) have shared features including vasculitis, ocular inflammation, interstitial lung disease, and arthritis but existing evidence indicates they are distinct conditions. Interestingly, the co-existence of GPA and RA has been described in the literature. Herein, we report two cases of GPA developing in patients with underlying RA and examine the relationship between the two conditions. Two cases of GPA that developed in patients with preexisting RA are described in detail. Additionally, PubMed was searched for articles in English showing an association of RA and GPA using keywords "rheumatoid arthritis, and vasculitis, and Wegener's, and ANCA, and granulomatosis polyangiitis." In addition to our two cases of RA and GPA overlap, 14 reports were identified in PubMed library from 1970 to 2020. Most of the cases were females (14/16, 88%), and had RA as the initial diagnosis (15/16, 94%). The mean age of RA diagnosis was 45.5 years, the mean age of GPA diagnosis was 52 years and the mean interval between both diagnoses was 101 months. Cyclophosphamide and steroid therapy were used in most of the cases. There are numerous reports of GPA and RA overlap in the literature. GPA should be considered in the differential diagnosis when vasculitis develops in patients with RA.