Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a rare autoimmune disease affecting small-to medium-sized vessels. Chronic hepatitis B virus (HBV) infection is typically associated with ANCA-negative vasculitis, making the coexistence of HBV and ANCA-positive vasculitis uncommon and diagnostically challenging. We report an 84-year-old woman presenting with lethargy and functional decline. Investigations showed elevated inflammatory markers, normocytic anaemia, and haemoproteinuria. Immunology revealed strongly positive myeloperoxidase (MPO)-ANCA, with reactive HBV surface antigen and low viral load (36 IU/mL). Kidney biopsy demonstrated pauci-immune glomerulonephritis with focal fibrocellular crescents. The patient was treated with oral corticosteroids and entecavir, followed by azathioprine maintenance. Rapid clinical and biochemical improvement was observed, with normalisation of inflammatory markers within one week and resolution of ANCA titres and haemoproteinuria by three months. Eighteen months later, she remains stable with an undetectable HBV viral load. This case highlights the need to consider AAV in patients with chronic HBV presenting with haemoproteinuria and systemic inflammation. Histological confirmation is crucial due to potential false-positive ANCA results. Combined antiviral and immunosuppressive therapy can be safe and effective with close monitoring.
Bonello et al. (Tue,) studied this question.