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

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. 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. 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. 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 +/- A 9.8 versus 29.7 +/- A 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 +/- A 5.1 versus 5.0 +/- A 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). 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.