Post-liver transplant Crohn's disease: graft tolerance but not self-tolerance?

Inflammatory bowel disease (IBD) rarely occurs de novo after liver transplantation, and when it does usually presents as ulcerative colitis in patients transplanted for primary sclerosing cholangitis. We present two patients who developed de novo Crohn's colitis two and three years after liver transplant for primary biliary cirrhosis (PBC) and chronic hepatitis B infection, respectively. Both were on maintenance immunosuppression with a calcineurin inhibitor and azathioprine with no evidence of allograft rejection. Investigations for enteric and opportunistic infection were negative. In the nontransplant setting, the development of IBD is likely multifactorial with an immune origin. In our cases, the immunosuppression was titrated to minimal levels when IBD developed. Clearly, although a significant degree of allograft tolerance can occur, autoimmune diseases can still develop elsewhere, suggesting selective immune tolerance.