Antineutrophil cytoplasmic antibodies (ANCA) can occur in patients with small blood vessel vasculitis, including granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), or eosinophilic granulomatosis with polyangiitis (EGPA), collectively referred to as ANCA-associated vasculitis (AAV). The pANCA pattern may also be observed in patients with inflammatory bowel disease, predominantly ulcerative colitis, usually in the absence of detectable MPO-ANCA reactivity. Positive results for ANCA demonstrate two main patterns: cytoplasmic (cANCA) and perinuclear (pANCA). These patterns are observed in a range of small vessel vasculitis conditions, all categorized under ANCA-associated vasculitis (AAV), which includes granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis.