Section 2 -

Controversial Inflammatory Conditions of the Small and Large Intestine Marie E. Robert Director, Program in Gastrointestinal Pathology Yale University School of Medicine New Haven, Connecticut, USA

The Small Intestine Celiac Disease Then and Now. Recent studies on celiac disease, more properly known as gluten sensitive enteropathy (GSE) have heightened the pathologist's awareness of intra-epithelial lymphocytes in duodenal biopsies. Mild histologic forms of GSE are now recognized with increased IEL's as the only histologic change. In this talk, both the classic morphology and "minimal deviation" GSE are discussed in detail, with special emphasis on the differential diagnosis and how to avoid over-diagnosing this disease. The Marsh-Oberhuber classification will be described, however, a more practical diagnostic terminology is recommended for use in pathology reports. Recent Advances Until recently celiac disease was a diagnosis that was made in Western countries with confidence on small bowel biopsies. The criteria for pathologic diagnosis required flat or near flat small bowel mucosa, usually accompanied by increased intra-epithelial lymphocytes (IEL) and lamina propria inflammation in biopsies taken distal to the duodenal bulb. Before 1990, a diagnosis of untreated GSE was not further considered in biopsies that did not show significant loss of villous height. Beginning around 1990 and continuing to the present, several changes in our understanding of GSE have permanently altered the diagnostic landscape and have eliminated the "gold standard" status of the small bowel biopsy These changes include 1) the recognition that latent or occult (minimally symptomatic) GSE in adults represents a large, previously unappreciated disease population. The revision of histologic criteria to include minimal inflammatory changes with intact or only mildly abnormal architecture as a part of the histologic spectrum of GSE. The discovery that tissue transglutaminase (tTG) is the target autoantigen of antibodies formed in GSE patients, and the subsequent development of a highly accurate diagnostic test for anti-tTG antibodies. Serological Testing for Celiac Disease (See Table) The ELISA based clinical test for IgA anti tTG antibodies has a high sensitivity and specificity (77%-100% and 91%-100% respectively, and has become the serological test of choice for GSE, largely replacing anti-gliadin and anti-endomysial antibody tests. While the anti-endomysial (EMA) test is as sensitive and specific as the anti-tTG test using human recombinant protein, the immunofluoresent test for EMA is labor intensive and relies on a more subjective interpretation than the newer anti-tTG test. Currently, the literature states that tTG and EMA tests are equivalent and equally useful as a single test. The anti-gliadin antibody test has always been the least accurate, with sensitivity and specificity ranging from 57%-100% and 47%-94% respectively. Sensitivity and Specificity of Serological Tests for Gluten Sensitive Enteropathy Test Sensitivity Specificity Anti-Tissue Transglutaminase (tTG) 77-100%* 91-100% Anti-Endomysial Antibodies (EMA) 86-100% 90-100% Anti-Gliadin Antibodies (AGA) 57-100% 47-94% * Includes both the guinea pig and human recombinant protein tests. The human recombinant protein test is more sensitive and specific. HLA testing to detect susceptible HLA phenotypes (DQ2 and DQ8) is also likely to have an increasing role in the diagnostic work up of GSE. The absence of DQ2 or DQ8 virtually excludes the diagnosis. Pathology of Celiac Disease Several basic concepts should be taken into account when examining biopsies for a possible diagnosis of celiac disease. Villous blunting is not specific for celiac disease. Varying degrees of small bowel inflammation and villous blunting are seen in numerous conditions. Conditions Showing Histologic Overlap with Gluten Sensitive Enteropathy Conditions Associated with Increased Intra-Epithelial Lymphocytes* Conditions Associated with Villous Blunting Helicobacter Pylori Gastritis Viral Gastroenteritis Autoimmune Enteropathy Tropical Sprue Refractory Sprue Protein Intolerance Bacterial Overgrowth Common Variable Immunodeficiency Microvillous Inclusion Disease Autoimmune Enteropathy Tropical Sprue Refractory Sprue Protein Intolerance Bacterial vergrowth Radiation/chemotherapy Nutritional Deficiencies Eosinophilic Gastroenteritis * Many, but not all conditions associated with increased IEL's also show diffuse villous blunting, hence their appearance in both columns. As Marsh and other workers have described, the classic flat small bowel architecture of severe mucosal injury is but one end of a spectrum of pathologic changes seen in patients with a "state of gluten sensitivity". The degree of mucosal abnormality seen in any one set of biopsies, whether mild or severe, does not correlate with the severity of clinical symptoms. Instead, there is evidence that it is the overall length of small intestine (duodenum, jejunum) involved that correlates with the severity of clinical findings. Because of the recognition of variable histologic severity, the terminology used in pathology reports has become unstandardized. To minimize confusion, a uniform language of diagnosis should be utilized. GSE is a disease of the proximal small intestine in most patients, with disease severity usually greatest in the duodenum and proximal jejunum. The ileum can be involved in severe cases, but is not a reliable site for biopsy diagnosis. Although the duodenal bulb is subject to artifactual villous blunting due to prominent Brunner glands, and H. pylori related inflammation, there may be value in duodenal bulb biopsies in detecting patchy and subtle disease that is absent in more distal biopsies in GSE patients on a low gluten diet. Because we now recognize subtle and patchy histological findings in GSE, one could argue that it is best to biopsy at least two sites, the second duodenum, the proximal jejunum, and the duodenal bulb in order to avoid sampling error. Proper orientation of biopsies greatly facilitates the evaluation of mucosal architecture. Pathology and Terminology for Reports The spectrum of histologic findings in celiac disease ranges from normal villous architecture with increased intra-epithelial lymphocytes as the only abnormality, to flat mucosa with crypt hyperplasia, increased intra-epithelial lymphocytes, epithelial injury, and increased lamina propria inflammation. The pathology will be illustrated during the lecture, and is amply described in any GI pathology texts. No system of reporting is perfect. However, the recommended terminology for pathology reports in this setting is the term "mucosal lesion" with the modifier mild, moderate or severe, corresponding to the degree of villous blunting. A note describing the changes and correlating the findings with whatever clinical information is available must accompany all such reports. A differential diagnosis should be included as appropriate. The term mucosal lesion is useful, because it does not require the absolute knowledge that the patient has celiac disease, but accurately describes the changes seen. Pathologists frequently do not have serological and other data at the time of sign out. The Marsh-Oberhuber Classification is useful as a study tool, and as a means of considering the biology of celiac disease. However, because of difficulties in distinguishing the early stages and because one cannot apply the type unless a definite diagnosis of celiac disease already exists, it is not useful for pathology reports in most practice settings. Nevertheless, pathologists should be familiar with the system, and specific centers may wish to utilize it. Marsh-Oberhuber Classification of Celiac Disease* TYPE IEL'S / 100 EPITHELIAL CELLS CRYPTS APPEARANCE OF VILLI Pre-Infiltrative Type 0 Normal (Less than 40) Normal Normal Infiltrative Type 1 Greater than 40 Normal Normal Hyperplastic Type 2 Greater than 40 Hypertrophic Normal Destructive Type 3a Greater than 40 Hypertrophic Mild Blunting Destructive Type 3b Greater than 40 Hypertrophic Moderate Blunting Destructive Type 3c Greater than 40 Hypertrophic Severe Blunting (Flat) Hypoplastic Type 4 Greater than 40 Atrophic Severe Blunting (Flat) *Types 0-2 are rarely seen and are present most frequently in patients with Dermatitis Herpetiformis, asymptomatic patients and first-degree relatives of patients with GSE. Types 3a-c are usually found in symptomatic GSE patients. Type 4 is rare and seen in refractory patients. Biopsies with normal architecture and increased intra-epithelial lymphocytes Biopsies with increased IEL's as the only abnormality pose a difficult dilemma for the pathologist. First, the perception of increased IEL's is fraught with interobserver error on H and E stains. At best, the finding is non-specific and must always be correlated with serology. The proportion of patients with these minimal histologic changes who will eventually develop severe histologic lesions and symptoms is unknown. A small study suggested that 4/12 (33%) people with "mild" changes on duodenal biopsies progress to GSE with flat mucosa upon follow up. However, in a much larger study with 8-25 years of follow up only 5/236 (2.1%) people with biopsies showing increased IEL's or slight reduction in villous/crypt ratio went on to develop GSE. The upper limit of normal for numbers of IEL's is 20 lymphocytes per 100 epithelial cells. Careful analysis using CD3 and gamma/delta T-cell stains and counting 300-500 epithelial cells in several studies show reasonable agreement, that IEL counts of > 25/100 epithelial cells (or a ratio greater than 1:4) merit raising the suspicion for "potential celiac disease". However, this kind of painstaking analysis is entirely impractical for the practice setting. An alternative approach has been used successfully, where IEL counts in villous tips on H and E sections (5 villi, 20 epithelial cells in each) can be used to get a rapid and comparable assessment of IEL's. In general, counts of 6-12 IEL/20 epithelial cells in the villous tips of architecturally normal mucosa are found in patients who have serological or other evidence of GSE. The IEL counts are lower than those found in untreated flat GSE biopsies, and higher than normal controls. The counts obtained using the villous tip method correspond well with previous studies finding that >29 IEL's/100 epithelial cells is abnormal. Despite these impressive results, it bears repeating that finding increased IEL's in architecturally normal duodenal biopsies is a sensitive, but by no means specific test for potential GSE. Overlap in the IEL counts occurs between GSE and non-GSE patients in all studies. Many studies do not have adequate control groups that include patients on NSAIDs or patients with H. pylori gastritis; two common conditions routinely associated with increased IEL's in at least the bulb and occasionally the second duodenum. In summary, with regard to biopsies with normal to near normal architecture and a perceived increase in IEL's or a clinical question of GSE: Perform a scan of villi and especially villous tips looking for diffuse or patchy increases in IEL's. Avoid areas of even small lymphoglandular complexes in your assessment, as these will falsely elevate the IEL counts. If an obvious increase in IEL's exists, there is usually no need to count cells. Counting can be done using the villous tip method in more subtle cases if desired, without resorting to CD3 stains. Since correlation with serology will be required in all cases, it makes no sense to spend excessive time or expense counting IEL's outside of a research setting. If an increase in IEL's is found, the pathology report will then contain descriptive diagnosis, such as "duodenal mucosa with preserved villous architecture and increased intra-epithelial lymphocytes" with a note recommending correlation with serological and other evidence of GSE. Intraepithelial Lymphocyte Counting Methods for Use in Architecturally Normal Duodenal Biopsies* Diagnosis IEL/100 Enterocytes (total of 300-500 cells counted) Upper limit of normal 20/100 25/100 H and E CD3 stain Borderline Increased 25-29/100 H and E or CD3 stain Definitely Increased >29/100 H and E or CD3 stain Diagnosis Villous tip method (5 Villi, 20 Enterocytes/villous tips, average counts) Upper limit of normal 5/20 H and E or CD3 Definitely Increased 6/20 H and E or CD3 *Avoid all LGC's **Average the sum for all 5 villous tips Refractory Sprue Refractory or "unclassified" sprue is the absent or incomplete clinical response to a gluten-free diet. Accidental gluten ingestion must be excluded as well as other causes of diarrhea or malabsorption, such as pancreatic insufficiency, concomitant collagenous colitis, lymphoma or other rare entities, such as adult-onset autoimmune enteropathy. Some patients with refractory sprue have abnormal T-cell phenotypes, with a loss of surface CD4, CD8 and T-cell receptors, and display monoclonal rearrangements of the TCR gene. These observations have lead to the idea that a significant proportion of refractory sprue cases represent a form of "in situ" or cryptic T-cell lymphoma. In addition, the risk of progression to overt T-cell lymphoma is increased in refractory sprue patients with abnormal intraepithelial lymphocytes. PCR studies to detect T cell receptor gene rearrangements can be performed on paraffin blocks. Finding a monoclonal T-cell population helps confirm the diagnosis of refractory sprue, although it is unclear what therapy should be applied. The prognosis for patients with refractory sprue is extremely poor, with most patients requiring long term TPN and steroids for survival. Histologically, small bowel biopsies in refractory sprue show moderate to severe villous flattening despite strict adherence to a gluten free diet. The lesions may be patchy and variable in distribution, or may involve the entire small bowel, including the ileum. In some cases, the histology is identical to responsive, untreated GSE. However, certain histologic features may predict a refractory course, such as collagenous sprue basal plasmacytosis and mucosal thinning (atrophy). Autoimmune Enteropathy Autoimmune enteropathy is a rare condition, most common in infants, characterized by protracted, watery diarrhea and malabsorption associated with variably severe small bowel mucosal lesions. There is usually a family history of autoimmune diseases in patients or their families. Although initially described as a disorder of the small bowel, it is clear that the colon may be involved. Anti-enterocyte antibodies are present in approximately 50% of cases and are a fairly specific marker of the disease. Children with this condition are often severely ill, requiring elemental diets and TPN to survive. The pathologic features in small bowel biopsies include variable flattening of the villi with an increase in the number of lamina propria plasma cells and sometimes neutrophils. The number of intraepithelial lymphocytes may be normal or slightly increased. Crypt hyperplasia is usually, but not always, present. The severity of the lesion has been shown to correlate with the level of circulating anti-enterocyte antibodies. Nonsteroidal Anti-Inflammatory Drug-Induced Injury NSAID's are associated with a number of gastrointestinal lesions, including ulceration throughout the gastrointestinal tract, non-ulcerating inflammatory changes, "diaphragm disease" in the small intestine, and microscopic colitis. Aside from the rare occurrence of diaphragm disease, the inflammatory changes seen in most forms of NSAID injury are entirely non-specific, and include increased lamina propria plasma cells, increased intraepithelial lymphocytes, neutrophilic infiltrates with cryptitis, and small erosions and ulcers. Diaphragm disease refers to numerous, thin web-like mucosal septae that project into the lumen of the small intestine, causing narrowing and obstruction. Histologically, they consist of mucosa with reactive epithelial changes, with or without surface erosions, and prominent submucosal fibrosis. The bands of fibrous tissue are usually oriented perpendicular to the surface of the mucosa. Mild chronic inflammation is often present. The Large Intestine Microscopic Colitis Microscopic colitis is an idiopathic clinical pathologic syndrome that consists of the triad of (1) chronic watery diarrhea associated with (2) a normal endoscopic appearance of the colon, and (3) two characteristic, but overlapping histologic patterns: lymphocytic or collagenous colitis. The first description of microscopic colitis was a report of collagenous colitis by Lindstrom in Sweden in 1976. He described a patient with chronic watery diarrhea, and a normal endoscopic exam whose biopsy revealed a collagen band underneath the epithelium in the rectal mucosa. The first description of what is now called lymphocytic colitis (then called microscopic colitis) was by Read et al. in 1980. In a paper entitled "Chronic diarrhea of unknown origin" Read described the investigation of 27 patients with severe chronic diarrhea. In eight of those patients, the only distinct clinical or pathologic finding was the presence of "mildly increased chronic inflammatory cells in the lamina propria" of colonic mucosal biopsies. The term "microscopic colitis" was proposed to describe this incidental finding. Microscopic colitis is seen predominantly in middle-aged women, many of whom have other autoimmune diseases. The male to female ratio is equal in lymphocytic colitis. Certain HLA phenotypes have been associated with microscopic colitis, and many medications, especially NSAIDs have been loosely or strongly associated with the development of microscopic colitis. Lymphocytic Colitis The pathologic findings in lymphocytic colitis consist of three features, seen in varying degrees. First and foremost is an increase in intraepithelial lymphocytes (IEL's). In early studies there was an average of 24 lymphocytes per 100 surface epithelial cells in biopsies from patients with lymphocytic colitis. This was a statistically significant increase over normals where the number has been reported to be between 4-10 lymphocytes per 100 epithelial cells. The second component is surface epithelial injury, which consists of a loss of the normal columnar shape, mucodepletion, and a flat or syncytial appearance of the surface epithelium. The crypt epithelium shows nuclear enlargement and a slight increase in mitotic activity. Finally, the lamina propria shows increased cellularity, due primarily to increased plasma cells with a fewer number of lymphocytes, eosinophils, and rarely neutrophils. In detailed studies morphometric analysis of mucosal biopsies demonstrated that in lymphocytic colitis the lamina propria is 20% more cellular than in normal controls. The predominant cell type in the lamina propria is the CD4 positive T-helper cell. In addition to the three main features described above, there are several pertinent negatives in the diagnosis of lymphocytic colitis. By definition no subepithelial collagen deposition should be present, otherwise the diagnosis by default would be collagenous colitis. Also, the mucosal architecture at low power is essentially normal with the minor exception being that occasional branched crypts are sometimes seen. However, other features typical of ulcerative colitis, such as crypt abscesses and basal plasmacytosis are absent in most patients. It must be stressed that the histologic triad of increased IELs, surface epithelial injury, and increased lamina propria cellularity, is characteristic of lymphocytic colitis but is by no means specific. Collagenous colitis The primary distinction between lymphocytic colitis and collagenous colitis is the presence of collagen deposition immediately beneath the epithelial basement membrane in collageneous colitis. Several studies have demonstrated that the inflammation and epithelial injury seen in collagenous colitis is remarkably similar to that seen in lymphocytic colitis. IELs are increased, although often to a lessor extent than in lymphocytic colitis. Lamina propria cells are likewise increased, however the proportion of types of inflammatory cells may be different. In collagenous colitis eosinophils may be markedly increased, and are sometimes seen infiltrating crypt and surface epithelium. Neutrophils and crypt abscesses are also slightly more common in collagenous colitis than in lymphocytic colitis. The pattern of surface epithelial injury in collagenous colitis is similar to lymphocytic colitis, with mucodepletion and flattening of the cell surface. However, a common and distinct finding in collagenous colitis is the separation of strips of surface epithelium from the abnormal collagen layer. The separation appears to occur after biopsy, as no inflammatory response is seen. This finding is so characteristic that the mere observation of separated strips of epithelium from the lamina propria should prompt a search for collagen deposition in the appropriate clinical setting. The collagen band consists predominantly of type VI collagen, and tenascin, with lesser amounts of collagen type I and III. Tenascin is a glycoprotein that is a marker of matrix remodeling. In addition, the trapped fusiform or stellate cells commonly seen within the collagen matrix have ultrastructural features consistent with activated pericrypt myofibroblasts Differential Diagnosis The differential diagnosis of microscopic colitis includes essentially all other inflammatory conditions of the colon. For the purposes of discussion, the differential diagnosis can be put into three broad categories, idiopathic inflammatory bowel disease (ulcerative colitis and Crohn's disease), infections, and drug reactions. Inflammatory Bowel Disease Crohn's disease and ulcerative colitis are usually easy to distinguish from microscopic colitis. Patients typically present with a different set of symptoms that includes abdominal pain and/or bloody diarrhea. In addition, the majority of patients with Crohn's disease and ulcerative colitis present in the first two to three decades of life, whereas microscopic colitis typically presents after the age of forty. Endoscopic abnormalities are almost always found in Crohn's disease and ulcerative colitis, particularly at initial presentation before the institution of therapy. Finally, the pathology of these idiopathic inflammatory bowel diseases is fairly distinct from that of microscopic colitis. Crohn's disease and ulcerative colitis are characterized by varying degrees of mucosal architectural distortion, with crypt branching, subcryptal plasmacytosis, crypt abscesses, erosions, ulceration, and granulomas in Crohn's disease. Despite these usually striking differences, the distinction between inflammatory bowel disease and microscopic colitis has recently been called into question, as will be discussed below. Infectious Colitis Infectious colitis can be difficult to distinguish from microscopic colitis on histological grounds alone. For example, in outbreaks of infectious diarrhea, biopsies taken from affected patients can reveal changes indistinguishable from what we now call lymphocytic colitis. More typically, biopsies from patients with bacterial infections reveal marked neutrophilic infiltrates and crypt abscesses. Resolving infections may have a subtler pattern of inflammation that resembles lymphocytic colitis. However, infectious diarrhea is usually easily distinguished from microscopic colitis by the self-limited time course and other clinical data, such as stool cultures. Drug Reactions Drug reactions as a category can be much more difficult to distinguish from lymphocytic and collagenous colitis. There are a plethora of medications that have diarrhea as a side effect. A relatively small subset of these medications is associated with histologic abnormalities in mucosal biopsies. Among these medications, non-steroidal anti-inflammatory (NSAID) substances are most commonly associated with gastrointestinal symptoms. Among their many toxic effects, several NSAID's have been associated with endoscopic and histologic changes identical to lymphocytic and collagenous colitis. Whether the association is coincidental or causal is not clear. In some reports patients respond entirely to withdrawal of NSAID's. In others symptoms and histologic changes persist despite withdrawal of NSAID's, even though the onset of symptoms was temporally related to beginning these medications. In practice, a history of NSAID use should be sought in patients with a new diagnosis of microscopic colitis. If possible, these medications should be discontinued prior to labeling the patient with a chronic colitic condition. Microscopic colitis: changing pathology dogma Since the initial descriptions and classification of microscopic colitis a number of workers have reported unusual pathologic findings that require us to rethink our original conception of these disorders. These findings can be divided into three main categories, which will be discussed here. The first change in pathology dogma relates to findings in small intestinal biopsies in patients with lymphocytic and collagenous colitis. Several studies have described increased intraepithelial lymphocytes in patients with lymphocytic and collagenous colitis. In addition, subepithelial collagen deposition has been described in the terminal ileum in patients with collagenous colitis. The second change in dogma since the early studies of microscopic colitis concerns the finding of focal "inflammatory bowel disease-like" changes in biopsies from patients with lymphocytic and collagenous colitis. As mentioned previously, one of the distinguishing features between microscopic colitis and Crohn's and ulcerative colitis is the lack of architectural distortion in the former. However, it is now well established that occasional branched crypts can be seen in either lymphocytic or collagenous colitis. A recent study found crypt abscesses in up to 30% of patients with microscopic colitis, and foci of Paneth cell metaplasia. Focal inflammatory bowel disease-like changes should not alter the interpretation if all other features, both clinical and histologic, point towards the diagnosis of microscopic colitis. The third and most intriguing change in pathology dogma is the association of microscopic colitis with prior or future Crohn's disease and ulcerative colitis. Crohn's disease has been reported to develop in patients whose prior biopsies showed features of lymphocytic colitis. Conversely, there are reports of the development of collagenous colitis in patients with long-standing ulcerative colitis. The possible association of microscopic colitis with the other two main forms of idiopathic inflammatory bowel disease is intriguing. At this time, there is not enough data to discern whether the association implies related pathogenesis, or simply reflects the occurrence of two common diseases in the same patient. In the future, it may be important to examine etiological relationships between these types of inflammatory bowel disease. HLA typing and other host genetic associations as well as environmental triggers may be common to all three diseases. References Marsh MN: Gluten sensitivity and latency: The histological background, in Auricchio S, Visakorpi JK (eds): Common Food Intolerances 1: Epidemiology of Coeliac Disease, Dyn Nutr Res Basel, Karger, 1992, pp 142-150. Marsh MN, Crowe PT: Morphology of the mucosal lesion in gluten sensitivity. Bailliere's Clin Gastroenterol 9:273-293, 1995. Corassa GR, Andreani ML, Biagi F, et al: Clinical, pathological, and antibody pattern of latent celiac disease: Report of three adult cases. Am J Gastroenterol 91:2203-2207, 1996. Fasano A: Clinical presentation of celiac disease in the pediatric population. Gastroenterology 128:S68-S73, 2005. Marsh MN: Gluten, major histocompatibility complex, and the small intestine: A molecular and immunobiologic approach to the spectrum of gluten sensitivity ('celiac sprue'). Gastroenterology 102:330-354, 1992. Oberhuber G, Granditsch G, Vogelsang H: The histopathology of celiac disease: time for a standardized report scheme for pathologists. Eur J Gastroenterol Hepatol 11:1185-1194, 1999. Dieterich W, Ehnis T, Bauer M, et al: Identification of tissue transglutaminase as the autoantigen of celiac disease. Nature Med 3:797-801, 1997. Dieterich W, Laag E, Schopper H, et al: Autoantibodies to tissue transglutaminase as predictors of celiac disease. Gastroenterology 115:1317-1321, 1998. Anderson RP, Degano P, Godkin AJ, et al: In vivo antigen challenge in celiac disease identifies a single transglutaminase-modified peptide as the dominant A-gliadin T-cell epitope. Nature Med 6:337-342, 2000. Collin P, Kaukinen K, Vogelsang H, et al: Antiendomysial and antihuman recombinant tissue transglutaminase antibodies in the diagnosis of celiac disease: A biopsy-proven European multicentre study. Eur J Gastroenterol Hepatol 17:85-91, 2005. Fasano A. Current approaches to diagnosis and treatment of celiac disease: an evolving spectrum. Gastroenterol 120:636-651, 2001. Rostom A, Dubé C, Cranney A, et al: The diagnostic accuracy of serologic tests for celiac disease: A systematic review. Gastroenterology 128:S38-S46, 2005. Hill ID: What are the sensitivity and specificity of serologic tests for celiac disease? Do sensitivity and specificity vary in different populations? Gastroenterology 128:S25-S32, 2005. Kagnoff MF: Overview and pathogenesis of celiac disease. Gastroenterology 128:S10-S18, 2005. Liu E, Rewers M, Eisenbarth GS: Genetic testing: Who should do the testing and what is the role of genetic testing in the setting of celiac disease? Gastroenterology 128:S33-S37, 2005. Dewar DH, Ciclitira PJ: Clinical features and diagnosis of celiac disease. Gastroenterology 128:S19-S24, 2005. Rubin CE, Brandborg LL, Phelps PC, et al: Studies of celiac disease: I. The apparent identical and specific nature of the duodenal and proximal jejunal lesion in celiac disease and idiopathic sprue. Gastroenterology 38:28, 1960. Marsh MN: Mechanisms of diarrhoea and malabsorption in gluten-sensitive enteropathy. Eur J Gastroenterol Hepatol 5:784-795, 1993. MacDonald WC, Brandborg L, Flick AL, et al: Studies of celiac sprue. IV: The response of the whole length of the small bowel to a gluten-free diet. Gastroenterology 47:573-589, 1964. Dickey W, Hughes DF: Histology of the terminal ileum in celiac disease. Scand J Gastroenterol 39:665-667, 2004. Kreuning J, Bosman FT, Kuiper G, et al: Gastric and duodenal mucosa in "healthy" individuals: An endoscopic and histopathological study of 50 volunteers. J Clin Pathol 31:69-77, 1978. Hasan M, Sircus W, Ferguson A: Duodenal mucosal architecture in non-specific and ulcer-associated duodenitis. Gut 22:637-641, 1981. Kreuning J, Wal AM, Kuiper G, et al: Chronic nonspecific duodenitis: A multiple biopsy study of the duodenal bulb in health and disease. Scand J Gastroenterol 24:16-20, 1989. Yardley JH: Pathology of chronic gastritis and duodenitis, in Goldman H, Appelman HD, Kaufman N, et al (eds): Gastrointestinal Pathology. Baltimore, William and Wilkins, 1990, pp 69-143. Vogelsang H, Hanel S, Steiner B, and Oberhuber G: Diagnostic duodenal bulb biopsy in celiac disease. Endoscopy 33:336-340, 2001. Ravelli A, Bolognini S, Gambarotti M, et al: Variability of histologic lesions in relation to biopsy site in gluten-sensitive enteropathy. Am J Gastroenterol 100:177-185, 2005. Lewin K, Riddell R, Weinstein W. Small bowel mucosal disease, in Lewin K, Riddell R, Weinstein W (eds): Gastrointestinal Pathology and its Clinical Implications. New York, NY, Igaku-Shoin, 1992, pp755-766. Halstensen TS, Scott H, Brantzaeg P: Intraepithelial T-cells of the TCR / + CD8- and V 1/J 1+ phenotypes are increased in celiac disease. Scand J Immunol 30:665-672, 1989. Savilahti E, Arato A, Verkasalo M: Intestinal, gamma/delta bearing T lymphocytes in celiac disease and inflammatory bowel diseases in children: Constant increase in celiac disease. Pediatr Res 28:579-581, 1990. Kutlu T, Brousse N, Rambaud C, et al: Numbers of T-cell receptor (TCR) / + but not of TCR / + intraepithelial lymphocytes correlate with the grade of villous atrophy in celiac patients on a long-term normal diet. Gut 34:208-214, 1993. Goldstein NS, Underhill J: Morphologic features suggestive of gluten sensitivity in architecturally normal duodenal biopsy specimens. Am J Clin Pathol 116:63-71, 2001. Lahdeaho Mll, Kaukinen K, Collin P, Tarja R, et al: Celiac disease: from inflammation to atrophy: a long-term follow up study. Gastroenterology, 41:44-48, 2005. Hayat M, Cairns A, Dixon MF, and O'Mahony S. Quantitation of intraepithelial lymphoyctes in human duodenum: what is normal? J Clin Pathol 55:393-395, 2002. Mahadeva S, Wyatt JI, Howdle: Is a raised intraepithelial lymphocyte count with normal duodenal villous architecture clinically relevant? J Clin Pathol 55:424-428, 2002. Mino M, Lauwers GY: Role of lymphocytic immunophenotyping in the diagnosis of gluten-sensitive enteropathy with preserved villous architecture. Am J Surg Pathol 27:1237-1242, 2003. Jarvinen TT, Collin P, Rasmussen M, Kyronpalo S, et al: Villous tip intraepithelial lymphocytes as a marker of early-stage coeliac disease. Scand J Gastroenterol 39:428-433, 2004. Veress, B, Franzen L, Bodin L, and Borch K: Duodenal intraepithelial lymphocyte-count revisited: Scand J Gastroenterol 39:138-144, 2004. Ferguson A, Murray D. Quantitation of intraepithelial lymphocytes in human jejunum: Gut 12:988-994, 1971. Biagi F, Luinetti O, Campanella J, Klersy C, Zambelli C, Villanacci et al: Intraepithelial lymphocytes in the villous tip: do they indicate potential coeliac disease? J Clin Pathol 57:835-839, 2004. Kakar S, Nehra V, Murray JA, et al: Significance of intraepithelial lymphocytosis in small bowel biopsy samples with normal mucosal architecture. Am J Gastroenterol 98:2027-2033, 2003. Memeo L, Jhang J, Hibshoosh H, et al: Duodenal intraepithelial lymphocytosis with normal villous architecture: Common occurrence in H. pylori gastritis. Mod Pathol 18:1134-1144, 2005. Chang F, Mahadeva U, Deere H: Pathological and clinical significance of increased intraepithelial lymphocytes (IELs) in small bowel mucosa. APMIS 113:385-399, 2005. Swanson VL, Thomassen RW: Pathology of the jejunal mucosa in tropical sprue. Am J Pathol 46:511-551, 1965. Perera DR, Weinstein WM, Rubin CE: Small intestinal biopsy. Hum Pathol 6:157-217, 1975. King CE, Toskes PP: Small intestine bacterial overgrowth. Gastroenterology 76:1035-1055, 1979. Robert ME, Ament ME, Weinstein WM: The histologic spectrum and clinical outcome of refractory and unclassified sprue. Am J Surg Pathol 24:676-687, 2000. Ament ME, Rubin CE: Soy protein: Another cause of the flat intestinal lesion. Gastroenterology 62:227-234, 1972. Ross IN: Primary immunodeficiency and the small intestine, in Marsh MN (ed): Immunopathology of the Small Intestine. New York, Wiley, 1987, pp 283-332. Weinstein WM: Intractable celiac sprue: Management, maintenance, and maladies, in Barkin J, Rogers A (eds): Difficult Decisions in Digestive Diseases. St. Louis, MO, Mosby, 1994, pp 257-263. Ryan BM, Kelleher D: Refractory celiac disease. Gastroenterology 119:243-251, 2000. Culliford AN and Green P: Refractory Sprue. Current Gastroenterology Reports 5:373-378, 2003. Daum S, Cellier C, and Mulder C. Refractory coeliac disease. Best Practice and Res Clin Gastroenterol 19:413-424, 2005. Corazza GR, Biagi F, Volta U, et al: Autoimmune enteropathy and villous atrophy in adults. Lancet 350:106-109, 1997. Fine KD, Meyer RL, Lee EL: The prevalence and causes of chronic diarrhea in patients with celiac sprue treated with a gluten-free diet. Gastroenterology 112:1830-1838, 1998. Murray A, Cuevas EC, Jones DB, et al: Study of the immunohistochemistry and T-cell clonality of enteropathy-associated T-cell lymphoma. Am J Pathol 146:509-519, 1995. Carbonnel F, Grollet-Bioul L, Brouet JC, et al: Are complicated forms of celiac disease cryptic T-cell lymphomas? Blood 92:3879-3886, 1998. Cellier C, Patey N, Mauvieux L, et al: Abnormal intestinal intraepithelial lymphocytes in refractory sprue. Gastroenterology 114:471-481, 1998. Bagdi E, Diss TC, Munson P, et al: Mucosal intra-epithelial lymphocytes in enteropathy-associated T-cell lymphoma, ulcerative jejunitis, and refractory celiac disease constitute a neoplastic population. Blood 94:260-264, 1999. Daum S, Weill D, Hummel M, Ullrich R, et al: Frequency of clonal intraepithelial T lymphocyte proliferations in enteropathy-type intestinal T cell lymphoma, coeliac disease, and refractory sprue. Gut 49:804-812, 2001. Daum S, Hummer M, Weiss D, Peters M, et al: Refractory sprue syndrome with clonal intraepithelial lymphocytes evolving into overt enteropathy-type intestinal T-cell lymphoma. Digestion 62:60-65, 2000. Goerres MS, Wahab Pj, Kerchaet JA et al. Cladribine treatment in refractory coeliac disease II. Gastroenterol 124: A16, 2003. Mulder CJ, Wahab Pj, Meijer JW and Meselaar E. A pilot study of recombinant human interleukin-10 in adults with refractory coeliac disease. Eur J Gastroenterol Hepatol 13:1183-1188, 2001. Weinstein WM, Saunders DR, Tytgat GN, et al: Collagenous sprue: An unrecognized type of malabsorption. N Engl J Med 283:1297-1301, 1970. Unsworth DJ, Walker-Smith JA: Autoimmunity in diarrheal disease. J Pediatr Gastroenterol Nutr 4:375-380, 1985. Carroccio A, Volta U, Di Prima L, et al: Autoimmune enteropathy and colitis in an adult patient. Dig Dis Sci 48:1600-1606, 2003. Leon F, Olivencia P, Rodriguez-Pena R, et al: Clinical and immunological features of adult-onset generalized autoimmune gut disorder. Am J Gastroenterol 99:1563-1571, 2004. Alarcon B, Regueiro JR, Arnaiz-Villena A, et al: Familial defect in the surface expression of the T-cell receptor-CD3 complex. N Engl J Med 319:1203-1208, 1988. Hill SM, Milla PJ, Bottazzo GF, et al: Autoimmune enteropathy and colitis: Is there a generalized autoimmune gut disorder? Gut 32:36-42, 1991. Mirakian R, Richardson A, Milla PJ, et al: Protracted diarrhea of infancy: Evidence in support of an autoimmune variant. Br Med J 293:1132-1136, 1986. Murch SH: The molecular basis of intractable diarrhea of infancy. Baillieres Clin Gastroenterol 11:413-438, 1997. von Hahn T, Stopik D, Koch M, et al: Management of severe refractory adult autoimmune enteropathy with infliximab and tacrolimus. Digestion 71:141-144, 2005. Bjarnason I, Zanelli G, Smith T, et al: Nonsteroidal anti-inflammatory drug-induced intestinal inflammation in humans. Gastroenterology 93:480-489, 1987. Allison MC, Howatson AG, Torrance CJ, et al: Gastrointestinal damage associated with the use of nonsteroidal anti-inflammatory drugs. N Engl J Med 327:749-754, 1992. Bjarnason I, Hayllar J, MacPherson AJ, et al: Side effects of nonsteroidal anti-inflammatory drugs on the small and large intestine in humans. Gastroenterology 104:1832-1847, 1993. Kessler WF, Shires GT III, Fahey TJ III: Surgical complications of nonsteroidal anti-inflammatory drug induced small bowel ulceration. J Am Coll Surg 185:250-254, 1997. Lang J, Price AB, Levi AJ, et al: Diaphragm disease: Pathology of disease of the small intestine induced by non-steroidal anti-inflammatory drugs. J Clin Pathol 41:516-526, 1988. Fellows IW, Clarke JMF, Roberts PF: Non-steroidal anti-inflammatory drug-induced jejunal and colonic diaphragm disease: A report of two cases. Gut 33:1424-1426, 1992. Lindstrom CG. 'Collagenous colitis' with watery diarrhoea: a new entity? Pathol Eur 1976;11:87-89. Weinstein WM, Saunders DR, Tytgat GN, et al. Collagenous sprue. An unrecognized type of malabsorption. NEJM 1970;283:1297-1301. Read NW, Krejs GJ, Read MG, et al. Chronic diarrhea of unknown origin. Gastroenterology 1980;78:264-271. Tagkalidis P, Bhathal P, Gibson P. Microscopic colitis. J Gastroenterol Hepatol 2002;17:236-248. Kingham JGC, Levison DA, Ball JA, et al. Microscopic colitis. A cause of chronic watery diarrhoea. Br Med J 1982;285:1601-1604. Bo-Linn GW, Vendrell DD, Lee E, et al. An evaluation of the significance of microscopic colitis in patients with chronic diarrhea. J Clin Invest 1985;75:1559-1569. Jessurun J, Yardley JH, Lee EL, et al. Microscopic and collagenous colitis: different names for the same condition? Gastroenterology 1986;91:1583-1585. Sanderson IR, Boyle S, Williams CB, et al. Histological abnormalities in biopsies from macroscopically normal colonoscopies. Arch Dis Child 1986;61:274-277. Jessurun J, Yardley JH, Giardiello FM, et al. Chronic colitis with thickening of the subepithelial collagen layer (collagenous colitis): histopathologic findings in 15 patients. Hum Pathol 1987;18:839-848. Lazenby AJ, Yardley JH, Giardiello FM, et al. Lymphocytic ("microscopic") colitis: a comparative histopathologic study with particular reference to collagenous colitis. Hum Pathol 1989;20:18-28. Lazenby AJ, Yardley JH, Giardiello FM, et al. Pitfalls in the diagnosis of collagenous colitis: experience with 75 cases from a registry of collagenous colitis at The Johns Hopkins Hospital. Hum Pathol 1990;21:905-910. Mosnier J-F, Larvol L, Barge J, et al. Lymphocytic and collagenous colitis. An immunohistochemical study. Am J Gastroenterol 1996;91:709-713. Lee E, Schiller LR, Fordtran JS. Quantification of colonic lamina propria cells by means of a morphometric point-counting method. Gastroenterology 1988;94:409-418. Lee E, Schiller LR, Ventrell D, et al. Subepithelial collagen table thickness in colon specimens from patients with microscopic colitis and collagenous colitis. Gastroenterology 1992;103:1790-1796. Foerster A, Fausa O. Collagenous colitis. Pathol Res Pract 1985;180:99-104. Bogomoletz WV. Collagenous colitis. A clinicopathological review. Surv Dig Dis 1983;1:19-25. Aigner T, Neureiter D, Muller S, et al. Extracellular matrix composition and gene expression in collagenous colitis. Gastroenterology 1997;113:136-143. Gunther U, Schuppan D, Bauer M, et al. Fibrogenesis and fibrolysis in collagenous colitis. Patterns of procollagen types I and IV, matrix-metalloproteinase-1 and -13, and TIMP-1 gene expression. Am J Pathol 1999;155:493-503. Hwang WS, Kelly JK, Shaffer EA, et al. Collagenous colitis. A disease of pericryptal fibroblast sheath? J Pathol 1986;149:33-40. Widgren S, Jlidi R, Cox JN. Collagenous colitis. Histologic morphometric immunohistochemical and ultrastructural studies. Report of 21 cases. Virch Archiv Anat 1988;413:287-296. Wang N, Dumot JA, Achkar E, et al. Colonic epithelial lymphocytosis without a thickened subepithelial collagen table. A clinicopathologic study of 40 cases supporting a heterogeneous entity. Am J Surg Pathol 1999;23:1068-1074. Carpenter HA, Tremaine WJ, Batts KP, et al. Sequential histologic evaluations in collagenous colitis: correlations with disease behavior and sampling strategy. Dig Dis Sci 1992;37:1903-1909. Bowling TE, Price AB, Al-Adnani M, et al. Interchange between collagenous and lymphocytic colitis in severe disease with autoimmune associations requiring colectomy. A case report. Gut 1996;38:788-791. Baert F, Wouters K, D'Haens G, et al. Lymphocytic colitis. A distinct clinical entity? A clinicopathological confrontation of lymphocytic and collagenous colitis. Gut 1999;45:375-381. Burgel N, Bojarski C, Mankertz J, et al. Mechanisms of diarrhea in collagenous colitis. Gastroenterology 2002;123:433-443. Stahle-Backdahl M, Malm J, Veress B, et al. Increased presence of eosinophilic granulocytes expressing transforming growth factor-ß1 in collagenous colitis. Scand J Gastroenterol 2000;7:742-746. Ung K-A, Gillberg R, Kilander A, et al. Role of bile acids and bile acid binding agents in patients with collagenous colitis. Gut 2000;46:170-175. Schiller LR, Bilhartz LE, Santa CA, et al. Comparison of endogenous and radiolabeled bile acid excretion in patients with idiopathic chronic diarrhea. Gastroenterology 1990;98:1036-1043. Schiller LR. Pathophysiology and treatment of microscopic-colitis syndrome. Lancet 2000;355:1198-1199. Bonner GF, Petras RE, Cheong DMO, et al. Short- and long-term follow-up of treatment for lymphocytic and collagenous colitis. Inflammatory Bowel Dis 2000;6:85-91. Fernández-Bañares F, Salas A, Esteve M, et al. Collagenous and lymphocytic colitis: evaluation of clinical and histological features, response to treatment, and long-term follow-up. Am J Gastroenterol 2003;98:340-347. Osterholm MT, MacDonald KL, White KE, et al. An outbreak of a newly recognized chronic diarrhea syndrome associated with raw milk consumption. JAMA 1986;256:484-490. Bryant DA, Mintz ED, Puhr ND, et al. Colonic epithelial lymphocytosis associated with an epidemic of chronic diarrhea. Am J Surg Pathol 1996;20:1102-1109. Jenkins AP, Trew DR, Crump BJ, et al. Do non-steroidal anti-inflammatory drugs increase colonic permeability? Gut 1991;32:66-69. Riddell RH, Tanaka M, Mazzoleni G. Non-steroidal anti-inflammatory drugs as a possible cause of collagenous colitis. A case-control study. Gut 1992;33:683-686. Beaugerie L, Luboinski J, Brousse N, et al. Drug induced lymphocytic colitis. Gut 1994;35:426-428. Mahajan L, Wyllie R, Goldblum J. Lymphocytic colitis in a pediatric patient. A possible adverse reaction to carbamazepine. Am J Gastroenterol 1997;92:2126-2127. Thomson RD, Lestina LS, Bensen SP, et al. Lansoprazole-associated microscopic colitis. A case series. Am J Gastroenterol 2002;97:2908-2913. Papadimitriou JC, Drachenberg CB, Beskow CO, et al. Graft-versus-host disease-like features in mycophenolate Mofetil-related colitis. Transpl Proc 2001;33:2237-2238. Padmanabhan V, Callas PW, Li SC, et al. Histopathological features of the terminal ileum in lymphocytic and collagenous colitis: a study of 32 cases and review of literature. Mod Pathol 2003;16:115-119. Sapp H, Ithamukkala S, Brien TP, et al. The terminal ileum is affected in patients with lymphocytic or collagenous colitis. Am J Surg Pathol 2002;26:1484-1492, 2002. Ayata G, Ithamukkala S, Sapp H, et al. Prevalence and significance of inflammatory bowel disease-like morphologic features in collagenous and lymphocytic colitis. Am J Surg Pathol 2002;26:1414-1423. Goldstein NS, Gyorfi T. Focal lymphocytic colitis and collagenous colitis: patterns of Crohn's colitis? Am J Surg Pathol 1999;23:1075-1081. Pokorny CS, Kneale KL, Henderson CJA. Progression of collagenous colitis to ulcerative colitis. J Clin Gastroenterol 2001;32:435-438.