BACKGROUND: MUC1-glycoprotein is expressed at low levels and in fully 
glycosylated form on epithelial cells. Inflammation causes MUC1 overexpression 
and hypoglycosylation. We hypothesized that overexpression of hypoglycosylated 
MUC1 would be found in postoperative Crohn's disease (CD) recurrence and could 
be considered an additional biomarker of recurrence severity.
METHODS: We examined archived neo-terminal ileum biopsies from patients with 
prior ileocecal resection who had postoperative endoscopic assessment of CD 
recurrence and given a Rutgeerts ileal recurrence score. Consecutive tissue 
sections were stained using 2 different anti-MUC1 antibodies, HMPV that 
recognizes all forms of MUC1 and 4H5 that recognizes only 
inflammation-associated hypoglycosylated MUC1.
RESULTS: A total of 71 postoperative CD patients were evaluated. There was 
significant increase in MUC1 expression of both glycosylated/normal (P<0.0001) 
and hypoglycosylated/abnormal (P<0.0001) forms in patients with severe 
endoscopic CD recurrence (i3+i4), ileal score i2, compared with patients in 
endoscopic remission (i0+i1). Results were similar regardless of anti-TNF-α use. 
Although MUC1 expression and Rutgeerts scores were in agreement when 
characterizing the majority of cases, there were a few exceptions where MUC1 
expression was characteristic of more severe recurrence than implied by 
Rutgeerts score.
CONCLUSIONS: MUC1 is overexpressed and hypoglycosylated in neo-terminal ileum 
tissue of patients with postoperative CD recurrence. Increased levels are 
associated with more severe endoscopic recurrence scores, and this is not 
influenced by anti-TNF-α use. Discrepancies found between Rutgeerts scores and 
MUC1 expression suggest that addition of MUC1 as a biomarker of severity of 
postoperative CD recurrence may improve categorization of recurrence status and 
consequently treatment decisions.