Atypical pANCA have been reported to occur in patients with IBD and primary sclerosing cholangitis (PSC). Studies have shown that ~80% of patients with UC and PSC and ~25% of patients with Crohn’s disease have pANCA.

Bacterial permealizing increasing factor (BPI) is one of the antigens associated with a pANCA reaction in patients with ulcerative colitis.

Differentiation of Crohn’s Disease (CD) and Ulcerative Colitis (UC) can be problematic clinically. ASCA and ANCA studies are useful in screening tests for inflammatory bowel disorders in differentiating UC from CD and in proper identification of patients with indeterminate colitis.

The staining pattern of ANCA in IBD is atypical pANCA. The prevalence of pANCA in UC is 50- 80% while in CD the prevalence is 10-20%. In contrast, ASCA occur primarily in CD (50-60%) and rarely in UC.