Overlapping systemic lupus erythematosus, seropositive erosive rheumatoid arthritis, and ANCA-associated vasculitis: A case report and literature review

ABSTRACT The overlap of rheumatoid arthritis and systemic lupus erythematosus is well described, with a syndrome known as ‘rhupus’. ANCA-associated vasculitis, however, is uncommonly associated with other autoimmune conditions. Here, we present a case of lupus, rheumatoid arthritis, and ANCA-associated vasculitis, with significant time elapsed between presentations, resulting in an accumulation of the three diagnoses over the course of 35 years. The patient was diagnosed with lupus at age 45, presenting with inflammatory polyarthritis, thrombocytopenia, leukopenia, positive ANA, positive anti-DNA, and hypocomplementemia. She was maintained on hydroxychloroquine therapy with minimal disease activity. Approximately 20 years later, she had a flare of polyarthritis with bilateral wrist erosive arthropathy and a positive rheumatoid factor, diagnosed as rheumatoid arthritis. Anti-TNFα therapy was initiated, and she was stable for a further 10 years. At age 79, she developed ANCA-associated vasculitis AAV with pulmonary and renal manifestations, treated with rituximab induction therapy and steroids. She recovered and her MPO-ANCA titre normalised. One year later, off the anti-TNFα, she again experienced an acute kidney injury with a repeat rise in MPO-ANCA. She was re-induced and maintained on steroids and rituximab. This novel case highlights the range of possible overlap syndromes, as well as how multiple autoimmune diagnoses can evolve over decades in previously stable disease. There is growing work around polyautoimmunity with ANCA-associated vasculitis and other systemic autoimmune diseases, which has potential to identify common aetiologies and pathogenesis. Knowledge of these overlap syndromes can help to recognise and manage these conditions in a timely manner.