Exploring ANCA Pathogenicity in Ulcerative Colitis: A Case Report Highlighting the Risk of Progression to ANCA-Associated Vasculitis.

Background: The relationship between anti-neutrophil cytoplasmic antibodies (ANCA) and inflammatory bowel disease has attracted significant attention due to shared immunopathological mechanisms and clinical associations. Case description: This case report describes a 20-year-old African woman with a history of ulcerative colitis who developed diffuse alveolar haemorrhage in the setting of elevated proteinase 3 (PR3)-ANCA. She was treated for ANCA-associated vasculitis with corticosteroids, plasma exchange, and rituximab, leading to a complete resolution. Conclusion: The case highlights the association between ulcerative colitis and ANCA-associated vasculitis, particularly with PR3-ANCA, and the importance of recognizing this overlap. Although ANCA are frequently present in inflammatory bowel disease, especially ulcerative colitis, their pathogenic role remains unclear. The incidence of ANCA-associated vasculitis is higher in inflammatory bowel disease patients, with ulcerative colitis often preceding ANCA-associated vasculitis. Despite the common presence of ANCA in inflammatory bowel disease, not all patients progress to ANCA-associated vasculitis. This case underscores the need for careful monitoring in ulcerative colitis patients with elevated PR3-ANCA and the role of ANCA in guiding diagnosis and treatment. LEARNING POINTS: High proteinase 3 (PR3)-anti-neutrophil cytoplasmic antibodies (ANCA) titre impacts the severity and management of ulcerative colitis patients.ANCA-associated vasculitis is more frequent in ulcerative colitis patients and occurs several years after ANCA positivity.Close monitoring of ulcerative colitis patients with PR3-ANCA is essential for early detection of progression to ANCA-associated vasculitis.