Clinical course of drug-induced collagenous colitis and histological changes after drug withdrawal in a Japanese case series

Although the incidence of drug-induced collagenous colitis has been increasing, details of its clinical course and histological changes after withdrawal of the suspected causative drugs remain unclear. To shed light on this issue, we studied 15 patients with collagenous colitis diagnosed between 1999 and 2011 in our hospital. Clinical cure was achieved in 14 patients after withdrawal of the suspected causative drugs and in one patient after the administration of prednisolone. Six patients underwent a second colorectal endoscopic examination after clinical cure, and the histological features were compared with those in patients during the clinically active phase. Four of these six patients showed disappearance of the collagen band and a decrease in inflammatory cells, but the collagen band remained in the other two despite a decrease in inflammatory cells. Cell proliferation as shown by Ki-67 immunostaining was restored to normal, irrespective of whether the collagen band was retained. The surface-absorptive epithelia became mature in all patients. Histological improvement in collagenous colitis is believed to involve normalization of cell proliferation and maturation of the absorptive epithelium, and not necessarily disappearance of the collagen band.