BACKGROUND: Cogan's syndrome (CSy) is a very rare autoimmune disorder, mainly affecting the inner ear and the eye, and is associated with inflammatory bowel disease (IBD).

METHODS: This was a European Crohn's and Colitis Organisation (ECCO) retrospective observational study, performed as part of the CONFER project. A call to all ECCO members was made to report concomitant CSy and inflammatory bowel disease (IBD) cases. Clinical data were recorded in a standardized questionnaire.

RESULTS: This international case series reports on 22 concomitant CSy-IBD cases from 14 large medical centres. Mean duration of IBD until diagnosis of CSy was 8.7 years (range 0.0-38.0) and mean age at CSy diagnosis was 44.6 years (range 9.0-67.0). Six patients had underlying ulcerative colitis (UC) and 16 had Crohn's disease. Eleven patients (50%) had active disease at CSy diagnosis. Sixteen patients were under IBD treatment at the time of CSy diagnosis, of whom 6 (37.5%) were on anti-tumour necrosis factor (TNF). Seven out of 10 patients, who were treated for CSy with immunomodulators (mostly with corticosteroids), demonstrated at least partial response.

CONCLUSION: This is the largest CSy-IBD case series so far. Although CSy is considered to be an autoimmune disease and is associated with IBD, immunomodulatory IBD maintenance treatment and even anti-TNF therapy do not seem to prevent disease onset. Moreover, IBD disease activity does not seem to trigger CSy. However, vigilance may prompt early diagnosis and directed intervention with corticosteroids at inception may potentially hinder audiovestibular deterioration. Finally, vigilance and awareness may also offer a better setting to study the pathophysiological mechanisms of this rare but debilitating phenomenon.