Letter: are lymphocytic colitis and collagenous colitis really the same disease?

Abstract

SIRS, We read the excellent systematic review performed by Ramussen et al. We agree with the authors that taken together, the findings suggest that collagenous colitis (CC) and lymphocytic colitis (LC) could represent histological phenotypes of the same disease. However, we have no definitive proof about that and, although there is some histological overlapping, it is also true that there are striking histological differences between both conditions. In fact, the intraepithelial lymphocyte (IEL) count in patients with CC is, in general, lower than that observed in LC. In our experience, using monoclonal antibodies against CD3 to facilitate IEL counting, the median IEL count in LC was 65% whereas in CC it was only 30% (P 5 but <10 μm, and therefore not achieving the cut-off value to diagnose CC. Immunostaining for tenascin may be of help in these cases. A thick tenascin-positive subepithelial band is observed in some patients suggesting that they have CC, whereas in LC the immunostaining is weak and discontinuous with a similar pattern to that observed in normal mucosa. In addition, there are data suggesting that the clinical course of LC differs from that of CC, since symptoms in LC are more likely to spontaneously disappear than those in CC. 5 In this sense, duration of symptoms before diagnosis appeared longer for CC patients than for LC patients. 7 Finally, although the response rate to budesonide was almost identical in both diseases, the response to placebo in budesonide-controlled trials has been higher in LC than in CC. Thus, a Cochrane metaanalysis showed a pooled placebo response of 17% in CC, whereas it was 48% in the only controlled trial performed in LC. 9 All these aspects argue against considering CC and LC as the same disease. The histological differentiation of both diseases remains of interest to further study their pathogenesis. The use of strict histological criteria, and thus the histological differentiation, is needed to avoid patients with mild nonspecific colonic inflammation being erroneously diagnosed as having microscopic colitis. Finally, if the placebo response rate is different, it may not be satisfactory to include CC and LC patients together in future clinical trials.