Rheumatoid arthritis and ANCA-associated vasculitis - an unusual overlap successfully treated with rituximab

Rheumatoid arthritis (RA) is among the most common inflammatory arthritis 1 .Despite a well-established association between RA and other autoimmune conditions, its overlap with anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) remains relatively rare 2 .Herein, we present a patient with long-standing RA who developed AAV with a rapidly progressive renal failure during the disease course.An 83 years-old man, with a background history of dyslipidaemia, arterial hypertension, and benign prostatic hyperplasia, had been under the care of our Rheumatology Department for more than 30 years following a diagnosis of erosive RA with positive rheumatoid factor and anti-citrullinated protein antibodies.He had lost follow-up in the prior two years, precipitated by the clinical disruptions caused by COVID-19.However, in his last appointment, he was in clinical remission under deflazacort 6 mg/day, methotrexate 10 mg/week, and sulfasalazine (SSZ) 1500 mg/day, which he maintained throughout his period of absence.After the two-year lapse in follow-up, he returned to our Rheumatology clinic.On physical examination, he had no swollen or tender joints but presented with symmetrical oedema of the lower limbs and increased arterial pressure (152/68 mmHg).Laboratory results showed normocytic normochromic anaemia (haemoglobin 9.5 g/dL), increased erythrocyte sedimentation rate (51 mm/h) and C-reactive protein (0.72 mg/dL), rise in serum creatinine (from a previous SCr 0.82 mg/