Lymphocytic Colitis and Collagenous Colitis: A Review of Clinicopathologic Features and Immunologic AbnormalitiesMahajan, Dipti MD*; Goldblum, John R. MD*; Xiao, Shu-Yuan MD†; Shen, Bo MD‡; Liu, Xiuli MD, PhD*Advances in Anatomic Pathology: January 2012 - Volume 19 - Issue 1 - p 28–38 doi: 10.1097/PAP.0b013e31823d7705 Review Articles Abstract Author Information Lymphocytic colitis (LC) and collagenous colitis (CC), 2 histologic forms of microscopic colitis, were recognized as rare disease entities 4 decades ago. An increasing body of evidence accumulated in the past 40 years reveals increasing incidence and prevalence rates, a wide spectrum of clinical presentations, and several histologic variants. Although several recent randomized clinical trials confirmed the efficacy of oral budesonide in treating LC and CC, disease relapse after a short-duration treatment is common. Despite their common clinical presentations and well-defined histologic diagnostic criteria, there are only few studies on the immunologic abnormalities in colonic tissue. The aim of this review is to (1) familiarize the pathologists in general practice with histomorphology of LC and CC, including the rare histologic variants and the clinical implication associated with these 2 diagnoses, (2) summarize the data from recent randomized clinical trials of oral budesonide, and (3) review immunological studies on colonic tissue. Overall, immunologic abnormalities of colonic tissue seem to explain for the histomorphologic features and the clinical symptomatology of LC and CC. Advances in the understanding of the underlying immunologic abnormalities in the colonic tissue may help develop novel and effective therapies for these 2 diseases. *Department of Anatomic Pathology ‡Department of Gastroenterology, Digestive Disease Institute, The Cleveland Clinic Foundation, Cleveland, OH †Department of Pathology, University of Chicago, Chicago, IL The authors have no funding or conflicts of interest to disclose. Reprints: Xiuli Liu, MD, PhD, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, 9500 Euclid Avenue/L25, Cleveland, OH 44195 (e-mail: Liux3@ccf.org).All figures can be viewed online in color at http://http://www.anatomicpathology.com. © 2012 Lippincott Williams & Wilkins, Inc.