**2.7 Perinuclear anti-neutrophil cytoplasmic antibodies p-ANCA**

Perinuclear anti-neutrophil cytoplasmic antibodies (p-ANCA) are a subset of anti-neutrophil cytoplasmic antibodies (ANCA) that target the heterogeneous collection of antigens, such as myeloperoxidase (MPO), cathepsin-G, elastase, lactoferrin, and bactericidal/permeability-increasing protein. p-ANCA mostly recognizes MPO, followed by neutrophil elastase, lactoferrin, and other antigens [58]. Atypical p-ANCA binds to those antigens in neutrophil granules leading to the staining of rim of the neutrophil nuclei and intranuclear foci [19]. p-ANCA is thought to be more dominant in UC than in Crohn's patients. For instance, p-ANCA has been detected in 40–80% of patients with ulcerative colitis compared to 5–25% of patients with Crohn's disease [58]. In addition, Smids et al. detected p-ANCA in 45% of UC patients, and only 5% of Crohn's patients [51]. Moreover, Ruemmele et al. state that p-ANCA are 92% specific for detecting ulcerative colitis, as those autoantibodies were absent in all non-IBD controls [59]. Smids also confirms p-ANCA specificity to UC (p = 0.0001) [51]. In addition to IBD, Freeman states that p-ANCA can also be present in patients with histologically-defined celiac disease with or without concomitant lymphocytic colitis [60]. Damoiseaux et al. also confirm the presence of p-ANCA in celiac disease patients as they detected its presence in 8 of 37 patients with celiac disease (21.6%) [27].
