CARD15 Mutations and Perianal Fistulating Crohn’s Disease: Correlation and Predictive Value of Antibiotic Response

BACKGROUND: CARD15 mutations alter bowel immunity and increase susceptibility to Crohn's disease (CD). However, the relation between these mutations and Crohn's perianal fistulas has not been fully clarified. AIMS: To assess whether CARD15 mutations are associated with risk of developing Crohn's perianal fistulas and whether these mutations are predictors of the response of perianal fistulas to antibiotics. METHODS: CARD15 mutations were investigated in 203 consecutive CD patients. Presence/absence of history of perianal fistula was recorded. Patients with history of perianal fistula were divided into two groups (with/without CARD15 mutations), and response to antibiotics was evaluated in both groups. RESULTS: Of the 203 patients, 60 (29.6%) showed at least one CARD15 mutation and 55 (27.1%) had history of perianal fistula. History of perianal fistula was identified in 13 (21.7%) patients with mutations and in 42 (29.4%) patients without mutations (P = 0.260). Mean age at diagnosis of first perianal fistula was similar in patients with/without CARD15 mutations (28.7 +/- 9.8 versus 29.7 +/- 10.1 years, P = 0.758). Average time between disease onset and diagnosis of first perianal fistula was also similar in the two groups (4.6 +/- 5.1 versus 5.0 +/- 5.9 years, P = 0.816). Response of perianal fistulas to antibiotics (metronidazole alone or combined with ciprofloxacin) was significantly higher in patients without CARD15 mutations (7.7% versus 40.5%, P = 0.041). CONCLUSIONS: In CD, CARD15 mutations are not associated with risk of developing perianal fistulas or with time of their outbreak. Nevertheless, patients with perianal fistulas and CARD15 mutations showed worse response to antibiotics