title: Isolated active ileitis: is it a mild subtype of Crohn's disease?
abstract: BACKGROUND
  Ileal intubation is being increasingly performed at colonoscopy and has in turn lead to an increasingly recognized subgroup of patients-those with mild terminal ileal inflammation, an entity that we have coined isolated active ileitis (IAI). The aims of this study were to define the natural history of IAI and determine if IAI shares a similar genetic and serologic profile with Crohn's disease (CD).
  
  
  METHODS
  Patients with IAI were identified from our institution's histopathology and endoscopy databases. Cases attended for repeat colonoscopy and blood were analyzed for the expression of antineutrophil cytoplasmic antibody, anti-OmpC, anti-Saccharomyces cerevisiae antigen (ASCA) IgA, ASCA IgG, and anti-CBir antibodies and NOD2 genotyping. Age and sex-matched healthy controls, CD, and UC cases were also recruited.
  
  
  RESULTS
  Sixty-three patients with IAI were recruited. There was no significant difference in the prevalence of antibodies between IAI cases and healthy controls for antineutrophil cytoplasmic antibody, OmpC, ASCA IgA, or ASCA IgG. The presence of all 5 antibodies was significantly higher in the CD group than the IAI group, P < 0.05. There were 28.6% of CD cases that carried one or more NOD2 variants, compared to 26.2% of the IAI cohort and 6.1% of healthy controls. Forty-three cases underwent follow-up ileocolonoscopy. Six of 43 cases (14%) had definite CD.
  
  
  CONCLUSIONS
  A majority of IAI cases developed persistent symptoms and terminal ileal abnormalities; however, only 14% developed classical, histological, or radiological features of CD. Although patients with IAI have a low level of seropositivity, similar to healthy controls, they do share an excess of NOD2 mutations with CD cases.
authors.affiliation: Department of Gastroenterology, AMNCH/Trinity College Dublin, Dublin, Ireland. odonnes2@tcd.ie
authors.forename: Sarah
authors.initials: S
authors.lastname: O'Donnell
authors.forename: Paul L
authors.initials: PL
authors.lastname: Crotty
authors.forename: Maria
authors.initials: M
authors.lastname: O'Sullivan
authors.forename: Niall
authors.initials: N
authors.lastname: Breslin
authors.forename: Humphrey J
authors.initials: HJ
authors.lastname: O'Connor
authors.forename: Colm A
authors.initials: CA
authors.lastname: O'Morain
authors.forename: Barbara M
authors.initials: BM
authors.lastname: Ryan
mesh_terms: D000328:Adult; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000097:blood; D015415:Biomarkers / Q000032:analysis*; D016022:Case-Control Studies; D003093:Colitis, Ulcerative / Q000097:blood / Q000235:genetics / Q000473:pathology*; D003424:Crohn Disease / Q000097:blood / Q000235:genetics / Q000473:pathology*; D005260:Female; D005500:Follow-Up Studies; D005838:Genotype; D006801:Humans; D007079:Ileitis / Q000097:blood / Q000235:genetics / Q000473:pathology*; D007070:Immunoglobulin A / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D053473:Nod2 Signaling Adaptor Protein / Q000235:genetics; D010641:Phenotype; D016133:Polymerase Chain Reaction; D011379:Prognosis; D012189:Retrospective Studies
chemical_list: D019268:Antibodies, Antineutrophil Cytoplasmic; D015415:Biomarkers; D007070:Immunoglobulin A; D007074:Immunoglobulin G; C429018:NOD2 protein, human; D053473:Nod2 Signaling Adaptor Protein