Mycophenolate mofetil-related gastrointestinal mucosal injury: variable injury patterns, including graft-versus-host disease-like changes. Am J Surg Pathol. 2008;32:1367-1372. [PMID: 18763324 DOI: 10.1097/pas.0b013e31816bf3fe]

Gastrointestinal tuberculosis following renal transplantation accompanied with septic shock and acute respiratory distress syndrome: a survival case presentation

BACKGROUND

Post-transplant tuberculosis (PTTB) is a serious opportunistic infection in renal graft recipients with a 30-70 fold higher incidence compared to the general population. PTTB occurs most frequently within the first years after transplantation, manifesting as pulmonary or disseminated TB. Gastrointestinal TB (GITB) is a rare and potentially lethal manifestation of PTTB and may show delayed onset in renal transplant recipients due to the use of lower doses of immunosuppressants. Further, non-specificity of symptoms and the common occurrence of GI disorders in transplant recipients may delay diagnosis of GITB.

CASE PRESENTATION

Here we report a rare survival case of isolated GITB in a renal transplant recipient, occurring seven years after transplantation. The patient's condition was complicated by severe sepsis with positive blood culture Staphylococcus haemolyticus, septic shock, multiple organ failure including acute respiratory distress syndrome (ARDS) and acute renal failure, requiring mechanical ventilation, vasopressor circulatory support and intermittent hemodialysis. Furthermore, nosocomial infections such as invasive aspergillosis and Pseudomonas aeruginosa occurred during hospitalization. Antituberculosis therapy (rifampicin, isoniazid, ethambutol and pyrazinamide) was initiated upon Mycobacterium confirmation. Moreover, treatment with voriconazole due to the Aspergillus flavus and meropenem due to the Pseudomonas aeruginosa was initiated, the former necessitating discontinuation of rifampicin. After 34 days, the patient was weaned from mechanical ventilation and was discharged to the pulmonary ward, followed by complete recovery.

CONCLUSION

This case offers a guideline for the clinical management towards survival of GITB in transplant patients, complicated by septic shock and multiple organ failure, including acute renal injury and ARDS.

Mucosal Biopsy After Bone Marrow Transplantation

Gastrointestinal mucosal biopsies in the hematopoietic stem cell transplantation setting are challenging because histologic features of graft-versus-host disease (GVHD), which is treated by increasing immunosuppression, overlap with those of other conditions, such as infection, which can get worse with GVHD treatment. More than one condition can occur at the same time. It is important to understand the histologic features of GVHD, drug toxicity, infection, and clinical factors surrounding patients, including timing of biopsy in relation to transplantation, medication history, and laboratory data. Rendering a correct diagnosis and generating a pathology report with standard language that can direct clinical management ensure proper management.

Deep Ulcers in the Ileum Associated with Mycophenolate Mofetil

A 54-year-old man was treated with mycophenolate mofetil (MMF) after undergoing living donor renal transplantation. Two years later, he experienced repeated episodes of diarrhea, and his C-reactive protein (CRP) level was found to be 12.63 mg/dL. Ileocolonoscopy showed multiple deep, punched-out ulcers that were similar to Behçet's disease (BD) and cytomegalovirus (CMV) in the ileum. CMV infection was suspected. However, anti-cytomegalovirus agents were ineffective. The patient was subsequently diagnosed with gastrointestinal toxicity of MMF and MMF was switched to mizoribine. His symptoms improved immediately, and his CRP level normalized. Six months later, the patient's mucosa was healed.

Clinical and Histologic Mimickers of Celiac Disease

Celiac disease is an autoimmune disorder of the small bowel, classically associated with diarrhea, abdominal pain, and malabsorption. The diagnosis of celiac disease is made when there are compatible clinical features, supportive serologic markers, representative histology from the small bowel, and response to a gluten-free diet. Histologic findings associated with celiac disease include intraepithelial lymphocytosis, crypt hyperplasia, villous atrophy, and a chronic inflammatory cell infiltrate in the lamina propria. It is important to recognize and diagnose celiac disease, as strict adherence to a gluten-free diet can lead to resolution of clinical and histologic manifestations of the disease. However, many other entities can present with clinical and/or histologic features of celiac disease. In this review article, we highlight key clinical and histologic mimickers of celiac disease. The evaluation of a patient with serologically negative enteropathy necessitates a carefully elicited history and detailed review by a pathologist. Medications can mimic celiac disease and should be considered in all patients with a serologically negative enteropathy. Many mimickers of celiac disease have clues to the underlying diagnosis, and many have a targeted therapy. It is necessary to provide patients with a correct diagnosis rather than subject them to a lifetime of an unnecessary gluten-free diet.

Pharmacokinetics and dynamics of mycophenolate mofetil after single-dose oral administration in juvenile dachshunds

Mycophenolate mofetil (MMF) is recommended as an alternative/complementary immunosuppressant. Pharmacokinetic and dynamic effects of MMF are unknown in young-aged dogs. We investigated the pharmacokinetics and pharmacodynamics of single oral dose MMF metabolite, mycophenolic acid (MPA), in healthy juvenile dogs purpose-bred for the tripeptidyl peptidase 1 gene (TPP1) mutation. The dogs were heterozygous for the mutation (nonaffected carriers). Six dogs received 13 mg/kg oral MMF and two placebo. Pharmacokinetic parameters derived from plasma MPA were evaluated. Whole-blood mitogen-stimulated T-cell proliferation was determined using a flow cytometric assay. Plasma MPA C_max (mean ± SD, 9.33 ± 7.04 μg/ml) occurred at <1 hr. The AUC_0-∞ (mean ± SD, 12.84±6.62 hr*μg/ml), MRT_inf (mean ± SD, 11.09 ± 9.63 min), T1/2 (harmonic mean ± PseudoSD 5.50 ± 3.80 min), and k/d (mean ± SD, 0.002 ± 0.001 1/min). Significant differences could not be detected between % inhibition of proliferating CD5+ T lymphocytes at any time point (p = .380). No relationship was observed between MPA concentration and % inhibition of proliferating CD5+ T lymphocytes (R = .148, p = .324). Pharmacodynamics do not support the use of MMF in juvenile dogs at the administered dose based on existing therapeutic targets.

Graft-versus-Host Disease of the Gut: A Histologic Activity Grading System and Validation

The pathologic interpretation of gut biopsies in hematopoietic cell transplant recipients to assess graft-versus-host disease (GVHD) is well accepted and supplements clinical and endoscopic findings. However, the histologic activity grading of GVHD is controversial, with attempts to predict prognosis or response to treatment largely unsuccessful. GVHD is being diagnosed earlier in its course, raising the possibility that the pathologic grading system can be profitably modified. We developed a histologic activity grading system designed to replace the commonly used modified Lerner grading systems. Our system stratifies the low-level Lerner grade I category into 4 activity grade categories, based on the average frequency of apoptotic cells. The results are expressed as ordinal categories: GVHD of minimal, mild, moderate, severe histologic activity, or severe histologic activity with destruction (activity grades 1 to 5). In a retrospective study, we studied 87 consecutive cases with 201 post-transplantation specimens (median, 48 days; range, 18 to 1479 days) of stomach, duodenum, and colorectum, which had been activity graded at the time of the original diagnosis. Most of the biopsies diagnosed as GVHD were low grade-minimal (11%) or mild (71%) histologic activity. We hypothesized that the higher activity grades would be associated with more therapeutic intervention. The odds of increased therapy in the combined all-site specimens were increased as activity grade increased (odds ratio, 2.9 [95% confidence interval {CI}, 1.9 to 4.5]; P = < .0001). Thus, our grading system was validated. To investigate whether the activity grade was associated with therapy within the formerly undivided Lerner grade I category, the analysis was restricted to these 174 all-site specimens. The validation result was similar (odds ratio, 3.1 [95% CI, 1.3 to 7.2]; P = .009). This result interestingly suggests that there is useful information hidden in the Lerner grade I category, which could potentially guide immediately actionable treatment decisions. This histologic activity grade system has been in use at our institution for over 2 years with good acceptance.

Histopathologic Features of Colitis Due to Immunotherapy With Anti-PD-1 Antibodies

Programmed cell death protein 1 (PD-1) blocking agents are novel immunotherapeutics used for treatment of advanced-stage malignancies. They have shown promise in the treatment of several malignancies, with greater efficacy and better tolerability than cytotoxic T-lymphocyte antigen 4 (CTLA-4) blocking agents. However, as with anti-CTLA-4 agents, clinically significant colitis remains an important complication. Although there is growing awareness of the histopathologic features of anti-CTLA-4 therapy, there is little information on the pathologic features of anti-PD-1 colitis. We describe here the histopathologic findings in 8 patients who developed colitis while on anti-PD-1 monotherapy. The most common pattern of injury observed (5/8 cases) was an active colitis with neutrophilic crypt microabscesses and with prominent crypt epithelial cell apoptosis and crypt atrophy/dropout. These latter features are reminiscent of other colitides with prominent apoptosis such as acute graft-versus-host disease or certain drug-induced colitides. The remainder of cases (3/8) showed a lymphocytic colitis-like pattern, characterized by increased intraepithelial lymphocytes and surface epithelial injury. Apoptosis was also often increased in these cases but crypt atrophy/dropout was not present. In patients who experienced recurrence of anti-PD-1 colitis, histologic features were similar to the initial insult but, in addition, features of chronicity developed that mimicked inflammatory bowel disease (basal lymphoplasmacytosis and crypt architectural irregularity, and Paneth cell metaplasia in 1 case). Awareness of the clinical scenario, however, should allow pathologists to suggest anti-PD-1 colitis. Interestingly, recurrent colitis was observed in patients who had been off anti-PD-1 therapy for many months. As anti-PD-1 agents are increasingly used in oncology, we present this series to increase awareness of anti-PD-1 colitis among pathologists, to facilitate its timely diagnosis and treatment.

Mycophenolate mofetil toxicity mimicking acute cellular rejection in a small intestinal transplant

Mycophenolate mofetil (MMF) is an important medication used for maintenance immunosuppression in solid organ transplants. A common gastrointestinal (GI) side effect of MMF is enterocolitis, which has been associated with multiple histological features. There is little data in the literature describing the histological effects of MMF in small intestinal transplant (SIT) recipients. We present a case of MMF toxicity in a SIT recipient, with histological changes in the donor ileum mimicking persistent acute cellular rejection (ACR). Concurrent biopsies of the patient’s native colon showed similar changes to those from the donor small bowel, suggesting a non-graft specific process, raising suspicion for MMF toxicity. The MMF was discontinued and complete resolution of these changes occurred over three weeks. MMF toxicity should therefore be considered as a differential diagnosis for ACR and graft-versus-host disease in SITs.

Spectrum of Drug-induced Chronic Diarrhea

The evaluation of a patient with chronic diarrhea can be quite frustrating, as it is expensive and involves multiple diagnostic studies. Moreover, identification of a drug as a cause of chronic diarrhea is a challenge in patients taking multiple medications. The disease may either be associated with intestinal mucosal changes, mimicking diseases such as celiac disease, or purely functional, with no histopathologic change. Drug-induced diarrhea may or may not be associated with malabsorption of nutrients, and a clinical improvement may occur within days of discontinuation of the drug, or may take longer when associated with mucosal injury. Diarrhea in diabetics, often attributed to poor management and lack of control, may be due to oral hypoglycaemic agents. Chemotherapy can result in diffuse or segmental colitis, whereas olmesartan and a few other medications infrequently induce a disease that mimics celiac disease, but is not associated with gluten intolerance. In short, increased awareness of a drug, as a cause for diarrhea and a clear understanding of the clinical manifestations will help clinicians to solve this challenging problem. This article aims to review drug-induced diarrhea to (a) understand known pathophysiological mechanisms; (b) assess the risk associated with frequently prescribed medications, and discuss the pathogenesis; and

Allograft biopsy findings in patients with small bowel transplantation

In this study, we sought to determine the incidence of post-transplant complications including acute cellular rejection (ACR), infection, and post-transplant lymphoproliferative disease (PTLD) in mucosal allograft biopsies in patients with small bowel transplant at our institution. We retrospectively reviewed pathology reports from 5675 small bowel allograft biopsies from 99 patients and analyzed the following: indications for biopsy, frequency and grade of ACR, the presence of infectious agents, results of workup for potential PTLD, results of C4d immunohistochemistry (IHC), features of chronic mucosal injury, and findings in concurrent native bowel biopsies. Findings from 42 allograft resection specimens were also correlated with prior biopsy findings. Indeterminate, mild, moderate, and severe ACR were seen in 276 (4.9%), 409 (7.2%), 100 (1.8%), and 207 (3.6%) of biopsies, respectively. Although ACR may show histologic overlap with mycophenolate mofetil toxicity, we found the analysis of concurrent native bowel biopsies to be helpful in this distinction. Adenovirus was the most common infectious agent seen (11%), and we routinely performed adenovirus IHC on biopsies. Eighteen patients (18%) developed PTLD, 83% of which were EBV associated, but only 28% of PTLD cases were diagnosed on mucosal allograft biopsies. C4d IHC did not correlate with the presence of donor-specific antibodies in limited cases.

Therapeutic targets and emerging treatment options in gastrointestinal acute graft-versus-host disease

Introduction

Graft-versus-host disease (GVHD) continues to be the major lethal complication of allogeneic hematopoietic stem cell transplantation (HCT) but the standard of care, high dose steroids, has not changed in 40 years. Approximately 50% of GVHD patients will develop steroid refractory disease, typically involving the gastrointestinal (GI) tract, which has a very poor prognosis. Newly developed GVHD biomarker-based risk scores provide the first opportunity to treat patients at the onset of symptoms according to risk of steroid failure. Furthermore, improvements in our understanding of the pathobiology of GVHD, its different signaling pathways, involved cytokines, and the role of post-translational and epigenetic modifications, has identified new therapeutic targets for clinical trials.

Areas covered

This manuscript summarizes the pathophysiology, diagnosis, staging, current and new targeted therapies for GVHD, with an emphasis on GI GVHD. A literature search on PubMed was undertaken and the most relevant references included.

Expert Opinion

The standard treatment for GVHD, high dose steroids, offers less than optimal outcomes as well as significant toxicities. Better treatments, especially for GI GVHD, are needed to reduce non-relapse mortality after allogeneic HCT. The identification of high risk patients through a biomarker-defined scoring system offers a personalized approach to a disease that still requires significant research attention.

Dabigatran-induced esophagitis: The prevalence and endoscopic characteristics

BACKGROUND AND AIM

There have been some descriptions of dabigatran-induced esophagitis in the literature. The aim of this study was to examine the prevalence and endoscopic characteristics of the disease.

METHODS

We reviewed the endoscopic database and medical records of 91 patients with dabigatran internal use who underwent upper gastrointestinal endoscopy. The frequency of dabigatran-induced esophagitis and its endoscopic findings were retrospectively analyzed. In addition, the clinical characteristics were compared between patients with dabigatran-induced esophagitis and those without the disease.

RESULTS

Dabigatran-induced esophagitis was found in 19 of 91 (20.9%) patients. Of the 19 patients with the esophagitis, 18 (94.7%) showed longitudinally sloughing epithelial casts in the mid and/or lower esophagus, which may be characteristic endoscopic findings of this disease. Symptomatic patients were more frequent in patients with dabigatran-induced esophagitis (68.4%) than those without (37.5%, P = 0.02). Other factors including age, gender, coexistence of hiatal hernia, gastroesophageal reflux disease, or concomitant other medications did not differ between the two groups.

CONCLUSIONS

Dabigatran causes the esophageal mucosal injury in approximately 20% of patients. Longitudinally sloughing casts in the distal esophagus are characteristic of dabigatran-induced esophagitis.

Idelalisib-associated Enterocolitis: Clinicopathologic Features and Distinction From Other Enterocolitides

Idelalisib is a highly specific small-molecule phosphoinositide-3-kinase δ inhibitor that was recently approved by the Food and Drug Administration for the treatment of chronic lymphocytic leukemia/small lymphocytic lymphoma and follicular lymphoma. The known side effects of idelalisib include severe diarrhea and colitis. Here we report the histologic findings in idelalisib-associated enterocolitis in 11 patients with chronic lymphocytic leukemia or follicular lymphoma receiving idelalisib over a 5-year period (2011 to 2015) at our institution. All 11 patients were receiving idelalisib and underwent colonoscopy for the evaluation of diarrhea. None of the patients had previously received a stem cell transplant. Histologically, the colon biopsies in all 11 cases showed some degree of apoptosis within crypts, with 5 cases showing moderate to severe apoptosis involving the majority of the crypts with loss of goblet cells. No viral inclusions were seen in any case and immunohistochemical stains for cytomegalovirus performed in 9/11 cases were negative. All cases showed at least focal acute cryptitis, and 8 of these cases showed mild architectural distortion. Increased inflammation within the lamina propria was seen in 7 cases, and increased intraepithelial lymphocytes within crypts was seen in 8 cases; the lymphocytes were mostly T cells with a predominance of CD8 T cells, with the majority expressing the α/β T-cell receptor. Diagnoses of graft-versus-host disease, autoimmune enteropathy, infectious enterocolitis, and although thought to be less likely, inflammatory bowel disease were considered in each case. The presence of numerous intraepithelial lymphocytes in addition to severe villous blunting and apoptosis in the small intestinal biopsies from a subset of these patients additionally raised the possibility of autoimmune enteropathy, common variable immunodeficiency, or less likely, celiac disease. Awareness of the histologic features of idelalisib-associated enterocolitis is important to distinguish it from potential mimics, particularly graft-versus-host disease, autoimmune enteropathy, and cytomegalovirus/infectious enterocolitis.

Iatrogenic pathology of the intestines

Many drugs and chemical agents can cause enteritis and colitis, producing clinical gastrointestinal side effects, the most common of which are diarrhoea, constipation, nausea and vomiting. Significant histological overlap exists between some patterns of medication or chemical injury and various disease entities. A particular medication may cause multiple patterns of injury and may mimic common entities such as coeliac disease, Crohn's disease, infectious enteritis and colitis. Thus, given the common absence of specific histopathological features, the diagnosis often relies upon thorough clinicopathological correlation. This review concentrates on selected examples of medication-induced injury of the intestinal tract in which the pathology can be recognized, particularly on biopsies, with a focus on newly described medication-induced gastrointestinal effects.

Acute graft-versus-host disease is more prevalent and severe in the lower than the upper gastrointestinal tract

It is unclear whether acute gastrointestinal (GI) graft-versus-host disease (GVHD) affects all segments of the GI tract equally. Up to 45% patients reported showed discrepancy in involvement between upper GI (UGI) and lower GI (LGI) tract. We compared the prevalence and the severity of acute GVHD in UGI and LGI tract on histologic examination. A cohort of 110 cases of simultaneous UGI and LGI biopsies from 105 allogeneic hematopoietic stem cell transplantation recipients with clinically confirmed GI GVHD were reviewed retrospectively. The χ(2) test and 1-way analysis of variance test were used for statistical analysis. Most (75%) of the cases had GVHD involvement in both UGI and LGI tracts, whereas UGI-only GVHD was found in 6% and LGI-only GVHD in 19%. GVHD prevalence was the lowest in stomach (61%) and significantly increased toward duodenum/jejunum (81%; P = .0019). The LGI tract showed similar GVHD prevalence (P = .3648); the highest was in the sigmoid colon (97%). The histologic grade was lowest in the stomach (mean ± SD, 1.6 ± 0.8) and was similar across all UGI segments (P = .0883). The histologic grade in LGI significantly increased (P = .0265) from the terminal ileum (2.0 ± 1.3) to the rectum (2.9 ± 1.0). Overall, both the prevalence and the histologic grade of GVHD in LGI were significantly higher than those of UGI (P < .0001 for both). Our results show that acute GVHD had a higher prevalence and was more severe in the LGI than in UGI tract. A small subset of patients had only UGI involvement.

Tacrolimus and mycophenolate mofetil associations

Gastrointestinal risk factors after organ transplantation are prevalent, due to the chronic use of immunosuppressant. The immunosuppressive drugs such as tacrolimus/mycophenolate mofetil (TAC/MMF) association are the most commonly used therapy. TAC and MMF have been implicated in gastrotoxicity, but their direct effects, alone and combined, on intestinal cells are not completely elucidated. This study investigated the effect of TAC and MMF alone and combined on human colon carcinoma cells. Our results demonstrated that TAC and MMF individually inhibit clearly cells proliferation, enhanced free radicals, lipid peroxidation production, induced DNA lesions and reduced mitochondrial membrane potential. In this study, we also showed that the two molecules TAC and MMF combined at high concentrations amplified the cell damage. Furthermore, the TAC (5 µM) prevented cell death induced by MMF (half maximal inhibitory concentration (IC50)). Also, MMF (50 µM) induced cytoprotection in HCT116 cells against TAC (IC50) toxicity. Our findings provide additional evidence that oxidative damage is the major contribution of TAC and MMF combined toxicities. In fact, MMF and TAC exert a gastroprotective effect by modulating reactive oxygen species production. These data underscore the pleiotropic effect of TAC and MMF on HCT116 cells that play a preventive and critical role on intestinal function.

NIH Consensus development project on criteria for clinical trials in chronic graft-versus-host disease: II. The 2014 Pathology Working Group Report

The 2005 National Institute of Health (NIH) Consensus Conference outlined histopathological diagnostic criteria for the major organ systems affected by both acute and chronic graft-versus-host disease (GVHD). The 2014 Consensus Conference led to this updated document with new information from histopathological studies of GVHD in the gut, liver, skin, and oral mucosa and an expanded discussion of GVHD in the lungs and kidneys. The recommendations for final histological diagnostic categories have been simplified from 4 categories to 3: no GVHD, possible GVHD, and likely GVHD, based on better reproducibility achieved by combining the previous categories of "consistent with GVHD" and "definite GVHD" into the single category of "likely GVHD." Issues remain in the histopathological characterization of GVHD, particularly with respect to the threshold of histological changes required for diagnostic certainty. Guidance is provided for the incorporation of biopsy information into prospective clinical studies of GVHD, particularly with respect to biomarker validation.

Coeliac-like duodenal pathology in orthotopic liver transplant patients on mycophenolic acid therapy

AIMS

Diarrhoea following orthotopic liver transplantation (OLT) is a significant clinical problem associated with mycophenolic acid (MPA). The histological injury pattern associated with MPA in the large bowel is well documented in the literature; however, that in the duodenum is less extensively documented. The aim of this study was to investigate the histological spectrum of duodenal injury specifically in symptomatic OLT patients on MPA, and to compare this with the spectrum in patients with coeliac disease and in normal controls.

METHODS AND RESULTS

We reviewed our pathology database for all duodenal biopsies from patients on the OLT list over a period of 19 years. Medical records, anti-tissue transglutaminase IgA serology and histology were reviewed. Of the 667 patients who underwent endoscopy, 127 had duodenal biopsies (152 biopsies). Of these, 87.5% were normal. Sixteen showed abnormal histology, and seven (43.8%) of these were on MPA at the time of biopsy. Significant features included coeliac-like changes (shortened villi and increased intraepithelial lymphocyte counts), and novel findings included increased endocrine cell counts, apoptotic counts and lamina propria eosinophil counts in comparison with normal duodenal biopsies.

CONCLUSIONS

Pathologists should be aware of the features of MPA-associated duodenal injury, including coeliac-like changes and increased apoptotic counts. In those with abnormal histology, discontinuation or a reduction in the dose of MPA should be discussed.

Gastrointestinal pathology in transplant patients

The assessment of gastrointestinal (GI) specimens from transplant patients is complicated by the wide range of potentially rare pathologies that may be found in this clinical setting. Acute GI graft-versus-host disease (GvHD) is characterized by epithelial cell apoptosis, although there is increasing recognition that acute and/or chronic inflammation may also be present. By contrast, thus far there are no histological features known to be specific to chronic GI GvHD. Mycophenolate mofetil colitis may mimic both GvHD and inflammatory bowel disease, whereas both cytomegalovirus (CMV) and adenovirus infections can cause gland apoptosis. Post-transplant lymphoproliferative disorder should be considered if a Crohn's-like histological picture is seen, and granulomas in biopsies from umbilical cord blood recipients should raise a suspicion of cord colitis syndrome. Finally, the GI tract may be involved directly or indirectly by the disease that originally required haematopoietic stem cell or liver transplantation.

Recipient pretransplant inosine monophosphate dehydrogenase activity in nonmyeloablative hematopoietic cell transplantation

Mycophenolic acid, the active metabolite of mycophenolate mofetil (MMF), inhibits inosine monophosphate dehydrogenase (IMPDH) activity. IMPDH is the rate-limiting enzyme involved in de novo synthesis of guanosine nucleotides and catalyzes the oxidation of inosine 5'-monophosphate to xanthosine 5'-monophosphate (XMP). We developed a highly sensitive liquid chromatography-mass spectrometry method to quantitate XMP concentrations in peripheral blood mononuclear cells (PMNCs) isolated from the recipient pretransplant and used this method to determine IMPDH activity in 86 nonmyeloablative allogeneic hematopoietic cell transplantation (HCT) patients. The incubation procedure and analytical method yielded acceptable within-sample and within-individual variability. Considerable between-individual variability was observed (12.2-fold). Low recipient pretransplant IMPDH activity was associated with increased day +28 donor T cell chimerism, more acute graft-versus-host disease (GVHD), lower neutrophil nadirs, and more cytomegalovirus reactivation but not with chronic GVHD, relapse, nonrelapse mortality, or overall mortality. We conclude that quantitation of the recipient's pretransplant IMPDH activity in PMNC lysate could provide a useful biomarker to evaluate a recipient's sensitivity to MMF. Further trials should be conducted to confirm our findings and to optimize postgrafting immunosuppression in nonmyeloablative HCT recipients.

Clinicopathologic features and outcome of mycophenolate-induced colitis in renal transplant recipients

Reports on the clinical course of mycophenolic acid (MPA)-related colitis in kidney transplant recipients are scarce. This study aimed at assessing MPA-related colitis incidence, risk factors, and progression after kidney transplantation. All kidney transplant patients taking MPA who had colonic biopsies for persistent chronic diarrhea, between 2000 and 2012, at the Kidney Transplantation Unit of Botucatu Medical School Hospital, Brazil, were included. Cytomegalovirus (CMV) immunohistochemistry was performed in all biopsy specimens. Data on presenting symptoms, medications, immunosuppressive drugs, colonoscopic findings, and follow-up were obtained. Of 580 kidney transplant patients on MPA, 34 underwent colonoscopy. Colonoscopic findings were associated with MPA usage in 16 patients. The most frequent histologic patterns were non-specific colitis (31.3%), inflammatory bowel disease (IBD)-like colitis (25%), normal/near normal (18.8%), graft-versus-host disease-like (18.8%), and ischemia-like colitis (12.5%). All patients had persistent acute diarrhea and weight loss. Six of the 16 MPA-related diarrhea patients (37.5%) showed acute dehydration requiring hospitalization. Diarrhea resolved when MPA was switched to sirolimus (50%), discontinued (18.75%), switched to azathioprine (12.5%), or reduced by 50% (18.75%). No graft loss occurred. Four patients died during the study period. Late-onset MPA was more frequent, and no correlation with MPA dose or formulation was found.

Changes in the small bowel of symptomatic kidney transplant recipients converted from mycophenolate mofetil to enteric-coated mycophenolate sodium

BACKGROUND/AIMS

Gastrointestinal (GI) symptoms in renal transplant recipients may be caused due to mycophenolic acid (MPA) toxicity. Using small bowel capsule endoscopy (SBCE) we examined the impact of conversion from Mycophenolate Mofetil (MMF) to enteric-coated formulation of Mycophenolate Sodium (EC-MPS) given to treat GI mucosal lesions.

METHODS

Adult kidney-only recipients at least 30 days after transplant, presenting with GI symptoms while receiving MMF completed a Gastrointestinal Symptom Rating Scale (GSRS) questionnaire, underwent SBCE, and had MMF substituted by EC-MPS. After 30 days, GSRS and SBCE were repeated and findings were compared to baseline values. Patients who were still on EC-MPS 6-24 months post-conversion were contacted for completing a follow-up GSRS questionnaire and SBCE.

RESULTS

Eighteen out of 23 subjects completed the first part of the study. Subjects' median ages and post-transplant time were 47.5 years old and 4.5 months, respectively. Tacrolimus, MMF and prednisone was the main regimen (94%), with a median MMF dose of 750 mg BID. The average baseline GSRS was 2.99 ± 0.81; it significantly decreased to 2.19 ± 0.8 at 30 days post-conversion. At baseline, 50 had gastric and 89% had small bowel lesions. At 30 days, 29 and 62% of the SBCE were still showing gastric and small bowel lesions, respectively. Of 5 patients in the study extension, 4 had abnormal SBCE findings but have been reporting improvement in their symptoms.

CONCLUSION

Stomach and small bowel mucosal lesions are common in kidney recipients with GI symptoms when treated with MMF. Conversion to EC-MPS for 30 days significantly alleviated the GI symptoms; however, no evident correlation with SBCE findings was found.

Hematopoietic stem cell transplantation: graft versus host disease and pathology of gastrointestinal tract, liver, and lung

Hematopoietic stem cell transplantation (HCT), formerly known as bone marrow transplantation, is an integral part of treatment for many hematological malignancies. HCT is associated with several complications and comorbidities with differential effects on a wide spectrum of organs and tissues. We present an update on HCT-associated complications such as graft versus host disease (GVHD) and infection, with focus on the surgical pathology of the gastrointestinal (GI) tract, liver, and lung. Although the grading system for GI tract acute GVHD was proposed 40 years ago, recent studies have shed light on minimal histologic criteria for diagnosis of GVHD, as well as its differential diagnosis, including histologic effects of various medications. GI dysfunction in autologous transplant recipients is increasingly appreciated and patients are often biopsied. Acute liver injury in HCT is often due to sinusoidal obstruction syndrome (previously known as venoocclusive disease), or acute GVHD. Liver dysfunction at later time posttransplantation may be associated with acute or chronic GVHD, iron overload, or other causes of hepatitis. Lung injury in HCT is multifactorial, and it remains crucially important to diagnose and treat pulmonary infections. The pulmonary biopsy yields clinically unsuspected diagnoses in the majority of cases and its utilization is likely to increase. The pathology of the skin and kidney in HCT patients are detailed in accompanying articles.

Acute colonic pseudo-obstruction caused by mycophenolate mofetil in a kidney transplant recipient

Mycophenolate mofetil is a component of immunosuppressive regimens in solid-organ transplant recipients. Gastrointestinal symptoms such as nausea, abdominal pain, and diarrhea without fever are common in patients treated with mycophenolate mofetil. We treated a patient who had acute colonic pseudo-obstruction after kidney transplant that resolved after discontinuing mycophenolate mofetil. The disorder recurred soon after resuming mycophenolate mofetil, which is evidence for an association between mycophenolate mofetil and acute colonic pseudo-obstruction in this patient.

Pharmacology and toxicology of mycophenolate in organ transplant recipients: an update

This review aims to provide an update of the literature on the pharmacology and toxicology of mycophenolate in solid organ transplant recipients. Mycophenolate is now the antimetabolite of choice in immunosuppressant regimens in transplant recipients. The active drug moiety mycophenolic acid (MPA) is available as an ester pro-drug and an enteric-coated sodium salt. MPA is a competitive, selective and reversible inhibitor of inosine-5'-monophosphate dehydrogenase (IMPDH), an important rate-limiting enzyme in purine synthesis. MPA suppresses T and B lymphocyte proliferation; it also decreases expression of glycoproteins and adhesion molecules responsible for recruiting monocytes and lymphocytes to sites of inflammation and graft rejection; and may destroy activated lymphocytes by induction of a necrotic signal. Improved long-term allograft survival has been demonstrated for MPA and may be due to inhibition of monocyte chemoattractant protein 1 or fibroblast proliferation. Recent research also suggested a differential effect of mycophenolate on the regulatory T cell/helper T cell balance which could potentially encourage immune tolerance. Lower exposure to calcineurin inhibitors (renal sparing) appears to be possible with concomitant use of MPA in renal transplant recipients without undue risk of rejection. MPA displays large between- and within-subject pharmacokinetic variability. At least three studies have now reported that MPA exhibits nonlinear pharmacokinetics, with bioavailability decreasing significantly with increasing doses, perhaps due to saturable absorption processes or saturable enterohepatic recirculation. The role of therapeutic drug monitoring (TDM) is still controversial and the ability of routine MPA TDM to improve long-term graft survival and patient outcomes is largely unknown. MPA monitoring may be more important in high-immunological recipients, those on calcineurin-inhibitor-sparing regimens and in whom unexpected rejection or infections have occurred. The majority of pharmacodynamic data on MPA has been obtained in patients receiving MMF therapy in the first year after kidney transplantation. Low MPA area under the concentration time from 0 to 12 h post-dose (AUC0-12) is associated with increased incidence of biopsy-proven acute rejection although AUC0-12 optimal cut-off values vary across study populations. IMPDH monitoring to identify individuals at increased risk of rejection shows some promise but is still in the experimental stage. A relationship between MPA exposure and adverse events was identified in some but not all studies. Genetic variants within genes involved in MPA metabolism (UGT1A9, UGT1A8, UGT2B7), cellular transportation (SLCOB1, SLCO1B3, ABCC2) and targets (IMPDH) have been reported to effect MPA pharmacokinetics and/or response in some studies; however, larger studies across different ethnic groups that take into account genetic linkage and drug interactions that can alter a patient's phenotype are needed before any clinical recommendations based on patient genotype can be formulated. There is little data on the pharmacology and toxicology of MPA in older and paediatric transplant recipients.

Palonosetron versus first-generation 5-hydroxytryptamine type 3 receptor antagonists for emesis prophylaxis in patients undergoing allogeneic hematopoietic stem cell transplantation

First-generation 5-hydroxytryptamine type 3 (5-HT3) receptor antagonists (RAs) are currently the standard of care for prophylaxis against allo-HSCT-induced emesis. However, the efficacy of this combination in allo-HSCT recipients is not entirely satisfying. We sought to compare the efficacy of first-generation 5-HT3 RAs with that of second-generation 5-HT3 RAs in emesis prevention in allo-HSCT recipients. A total of 51 consecutive patients undergoing allo-HSCT for various hematological diseases in our institution were retrospectively reviewed. Patients who received daily first-generation 5-HT3 RAs, and 60-h palonosetron for emesis prophylaxis were stratified into the standard (n = 23) and palonosetron (n = 28) groups, respectively. Emesis severity and rescue therapy requirements in patients between these two groups were compared. Our results showed patients in standard and palonosetron groups had comparable severity of both acute and delayed emesis. However, 52.2 % of the patients in the standard group required rescue therapy, compared to only 21.4 % of the patients in the palonosetron group (p = 0.046). Subgroup analysis showed rescue therapy for acute emesis was required by 26.1 % of the patients in the standard group and by only 3.6 % of the patients in the palonosetron group (p = 0.037). In conclusion, palonosetron and first-generation 5-HT3 RAs were at least equally effective in emesis prophylaxis for allo-HSCT recipients. Patients receiving palonosetron, especially for acute emesis, required rescue therapy less frequently than those receiving first-generation 5-HT3 RAs.

A practical approach to small bowel biopsy interpretation: celiac disease and its mimics

While celiac disease is the most common cause of villous remodeling and intraepithelial lymphocytosis in the proximal small bowel, there are many entities that can mimic its histologic appearance. The purpose of this review is to discuss normal small bowel histology and the differential diagnosis of celiac disease. Approaches to evaluate increased intraepithelial lymphocytes are presented, followed by a detailed discussion of the pathology of celiac disease. Particular emphasis is given to those conditions that cause intraepithelial lymphocytosis in the setting of preserved villous architecture, although other important entities, such as peptic injury, idiopathic inflammatory bowel disease, medication injury, eosinophilic (allergic) gastroenteritis, autoimmune enteropathy, common variable immunodeficiency, and infections are also reviewed.

Drug-induced injury in the gastrointestinal tract

Abnormalities of the gastrointestinal tract due to drug-induced injuries are common and often have important clinical consequences. Medications may cause damage by direct corrosive effects on mucosae or by alter processes, mucosal immunity, and local environmental conditions. The aim of this review is to guide practicing pathologists in the identification of drug-related injuries in gastrointestinal mucosal biopsies and resection specimens. Common causes of injury and their gross, endoscopic, and microscopic features are presented.

Mycophenolic acid mediated disruption of the intestinal epithelial tight junctions

Gastrointestinal toxicity is a common adverse effect of mycophenolic acid (MPA) treatment in organ transplant patients, through poorly understood mechanisms. Phosphorylation of myosin light chain 2 (MLC2) is associated with epithelial tight junction (TJ) modulation which leads to defective epithelial barrier function, and has been implicated in GI diseases. The aim of this study was to investigate whether MPA could induce epithelial barrier permeability via MLC2 regulation. Caco-2 monolayers were exposed to therapeutic concentrations of MPA, and MLC2 and myosin light chain kinase (MLCK) expression were analyzed using PCR and immunoblotting. Epithelial cell permeability was assessed by measuring transepithelial resistance (TER) and the flux of paracellular permeability marker FITC-dextran across the epithelial monolayers. MPA increased the expression of MLC2 and MLCK at both the transcriptional and translational levels. In addition, the amount of phosphorylated MLC2 was increased after MPA treatment. Confocal immunofluorescence analysis showed redistribution of TJ proteins (ZO-1 and occludin) after MPA treatment. This MPA mediated TJ disruption was not due to apoptosis or cell death. Additionally ML-7, a specific inhibitor of MLCK was able to reverse both the MPA mediated decrease in TER and the increase in FITC-dextran influx, suggesting a modulating role of MPA on epithelial barrier permeability via MLCK activity. These results suggest that MPA induced alterations in MLC2 phosphorylation and may have a role in the patho-physiology of intestinal epithelial barrier disruption and may be responsible for the adverse effects (GI toxicity) of MPA on the intestine.

Histologic features in colon biopsies can discriminate mycophenolate from GVHD-induced colitis

Mycophenolate mofetil (MMF) is a T-cell inhibitor frequently used in the treatment of acute allograft rejection. MMF may cause colitis that clinically and histologically resembles graft-versus-host disease (GVHD). The aim of this study was to evaluate a wide range of histologic features that may help differentiate MMF from GVHD-induced colitis and to validate significant features on a cohort of bone marrow transplant patients who were also taking MMF as part of their immunosuppressive regimen and developed a diarrheal illness due to colitis. Routinely processed colonic biopsies from 17 patients with MMF colitis and 40 patients with GVHD-induced colitis were evaluated for the overall grade of colitis (grades 1 to 4) and histologically for a wide range of inflammatory, epithelial, and architectural changes in a blinded manner. Statistically significant features were then tested in a cohort of 20 bone marrow transplant patients who also received MMF, and later developed a diarrheal illness. Both univariate and multivariate analyses (including receiver operating characteristic analysis) were performed. Morphologic features shown to be independently associated with MMF include the presence and quantity of lamina propria eosinophils and endocrine cell aggregates and the presence and quantity of apoptotic microabscesses, hypereosinophilic (degenerated) crypts, and crypt distortion. Eosinophils were present in all MMF patients, but apoptotic microabscesses were present in none and endocrine cell aggregates in only 1 case. When a grade-by-grade comparison was made between MMF and GVHD, grade 1 or 2 MMF also showed an increased prevalence rate and quantity of lamina propria neutrophils in comparison with grade 1 or 2 GVHD. By receiver operating characteristic analysis, a combination of lamina propria eosinophils >15 per 10 HPF, combined with a lack of endocrine cell aggregates and apoptotic microabscesses, revealed sensitivity, specificity, and positive and negative predictive values of 76%, 93%, 81%, and 90%, respectively, for identification of MMF colitis. On the basis of these data, we conclude that a variety of histologic features, in particular, eosinophils >15 per 10 HPF, lack of endocrine cell aggregates in the lamina propria, and lack of apoptotic microabscesses, can be used by pathologists to help separate MMF from GVHD-induced colitis in routine clinical practice.

Ulcerative colitis or Crohn's disease? Pitfalls and problems

The interpretation of colorectal biopsies taken for the initial diagnosis of chronic idiopathic inflammatory bowel disease (IBD) is challenging. Subclassification of IBD as ulcerative colitis (UC) or Crohn's disease, which may be particularly difficult, is the subject of this review. Biopsies taken at first presentation are emphasised, partly because their features have not been modified by time or treatment. Aspects of longstanding disease and of resections are also mentioned. The first part of the review comprises background considerations and a summary of histological features that are discriminant, according to published evidence, between UC and Crohn's disease in initial biopsies. Pitfalls and problems associated with making the distinction between UC and Crohn's disease are then discussed. These include: mimics of IBD; inadequate clinical details; unreliable microscopic features; absence of histological changes in early IBD; discontinuity in UC; cryptolytic granulomas; differences between paediatric and adult UC; reliance on ileal and oesophagogastroduodenal histology; and atypical features in IBD resections. Avoidance by pathologists of known pitfalls should increase the likelihood of accurate and confident subclassification of IBD, which is important for optimum medical and surgical management.

Diarrhea in solid-organ transplant recipients: a review of the evidence

OBJECTIVE

To provide a comprehensive review of the literature as it relates to diarrhea in solid organ transplant (SOT) recipients. In this article, we review the epidemiology, pathogenesis, clinical manifestations, diagnosis and management of diarrhea in SOT recipients and discuss recent advances and challenges.

METHODS

Two investigators conducted independent literature searches using PubMed, Web of Science, and Scopus until January 1st, 2013. All databases were searched using a combination of the terms diarrhea, solid organ transplant, SOT, transplant associated diarrhea, and transplant recipients. Articles that discussed diarrhea in SOT recipients were reviewed and relevant cross-references also read and evaluated for inclusion. Selection bias could be a possible limitation of the approach used in selecting or finding articles for this article.

FINDINGS

Post-transplant diarrhea is a common and distressing occurrence in patients, which can have significant deleterious effects on the clinical course and well-being of the organ recipient. A majority of cases are due to infectious and drug-related etiologies. However, various other etiologies including inflammatory bowel disease must be considered in the differential diagnosis. A step-wise, informed approach to post-transplant diarrhea will help the clinician achieve the best diagnostic yield. The use of diagnostic endoscopy should be preceded by exclusion of an infectious or drug-related cause of diarrhea. Empiric management with antidiarrheal agents, probiotics, and lactose-free diets may have a role in managing patients for whom no cause can be determined even after an extensive investigation.

CONCLUSIONS

Physicians should be familiar with the common etiologies that result in post-transplant diarrhea. A directed approach to diagnosis and treatment will not only help to resolve the diarrhea but also prevent potentially life-threatening consequences including loss of the graft as well. Prospective studies are required to determine the etiology of post-transplant diarrhea in different clinical and geographic settings.

Prevalence of graft versus host disease and cytomegalovirus infection in patients post-haematopoietic cell transplantation presenting with gastrointestinal symptoms

BACKGROUND

There is lack of consensus regarding whether both upper and lower endoscopic examinations are required for diagnosis of gastrointestinal acute graft versus host disease (GI-AGVHD).

AIM

To evaluate the impact of endoscopic procedures on the diagnosis of GI-AGVHD.

METHODS

We performed a retrospective case-control study of recipients of allogeneic haematopoetic cell transplant (HCT) from 2000 to 2011, who presented with GI symptoms between 20 and 125 days post-HCT. GI-AGVHD status was based on the National Institutes of Health (NIH) clinical grading system.

RESULTS

One hundred and twenty-nine clinical GI-AGVHD cases and 184 controls underwent endoscopic examinations. Diarrhoea was present in 73% of cases and 38% of controls (P < 0.0001); 99% of patients with nausea ± vomiting and diarrhoea underwent bidirectional endoscopy. Histology had a sensitivity of 92% and specificity of 91% compared to the clinical criteria. The sensitivity for GI-AGVHD was 80% or greater when upper endoscopy (EGD) was performed with either sigmoidoscopy or colonoscopy, or if lower endoscopic examinations were performed alone. The sensitivity of EGD alone was only 48% (P = 0.003). Sensitivity was highest with biopsy of the terminal ileum (79%), followed by the ascending (74%), transverse/descending (73%) and sigmoid colons (69%). Diagnostic yield for cytomegalovirus (CMV) infection was equivalent for biopsies from both upper and lower GI tracts. Patients found to have concurrent GI-AGVHD and CMV infection (N = 18) had a poorer overall prognosis.

CONCLUSION

In patients post-HCT with GI symptoms, sigmoidoscopy alone had equivalent diagnostic yield for GI-AGVHD and CMV infection, compared with the addition of EGD or performance of full colonoscopy.

Histological spectrum of mycophenolate mofetil-related colitis: association with apoptosis

AIMS

The main purpose of this study was to define diagnostic histological characteristics of mycophenolate mofetil (MMF)-related colitis in association with crypt epithelial cell turnover.

METHODS AND RESULTS

The examined material included 43 colonic biopsies from renal transplant recipients with MMF administration and persistent diarrhoea. Thirty-three cases showed MMF-related colitis, while 10 showed no significant changes. The histological findings were scored and correlated with the apoptotic index (AI) and with the proliferation rate (PR) of the crypt epithelium examined by TUNEL assay and Ki-67 immunoexpression. Ten cases of Crohn disease and 10 of ulcerative colitis were used as comparative groups. Crypt distortion and loss as well as increased apoptosis constituted the main features, their degree and combination leading either to an inflammatory bowel disease (IBD)-like (82%) or to a graft-versus-host disease-like pattern (18%). A high AI was associated more frequently with moderate and severe crypt distortion, while the values were significantly higher compared with the control groups (P < 0.01). High PR was noted in 18 of 29 (62.1%) of the cases.

CONCLUSIONS

The diagnostic hallmark of MMF-related colitis is an IBD-like histological pattern in association with increased epithelial apoptosis, while apoptotic cell death seems to be a potential pathogenetic factor of mucosa injury.

Inflammatory bowel disease biopsies: updated British Society of Gastroenterology reporting guidelines

Accurate histopathological assessment of biopsies is important for the diagnosis, subclassification, and management of chronic idiopathic inflammatory bowel disease (IBD). British Society of Gastroenterology (BSG) guidelines for the initial histopathological diagnosis of IBD were published in 1997. Changes since then include: more widespread use of full colonoscopy; greater recognition of the effects of time and treatment; improved documentation of variations in anatomical distribution; better understanding of the mimics of IBD; significant progress in clinical management; and modifications of terminology. Accordingly, an update is required. These revised guidelines aim to optimise the quality and consistency of reporting of biopsies taken for the initial diagnosis of IBD by summarising the literature and making recommendations based on the available evidence. Advice from existing clinical guidelines is also taken into account. Among the subjects discussed are: distinguishing IBD from other colitides, particularly infective colitis; subclassification of IBD (as ulcerative colitis, Crohn's disease, or IBD unclassified); the discriminant value of granulomas; aspects of disease distribution, including discontinuity in ulcerative colitis; time-related changes; differences between paediatric and adult IBD; the role of ileal and upper gastrointestinal biopsies; differential diagnoses such as diverticular colitis and diversion proctocolitis; and dysplasia. The need to correlate the histological features with clinical and endoscopic findings is emphasised. An approach to the conclusion of an IBD biopsy report based on the acronym Pattern, Activity, Interpretation, Dysplasia (PAID) is suggested. The key recommendations are listed at the end of the document.

De novo inflammatory bowel disease and its mimics after organ transplantation

Diarrhea is a common symptom after solid organ transplantation or hematopoietic stem cell transplantation, with a reported prevalence up to 72%. One of the uncommon causes for diarrhea in the posttransplant setting is development of de novo inflammatory bowel disease (IBD). The incidence of posttransplantation de novo IBD was shown to be higher than that in the general population (206 versus 20 per 100,000 cases annually). The frequency seems to be much higher following orthotopic liver transplantation than the transplantation of other solid organs. De novo IBD has also been described in the setting of bone marrow transplantation though not as commonly as after SOT. While IBD is considered an immune-mediated disorder and responds favorably to immunosuppressive, de novo IBD or IBD-like conditions can occur in the posttransplant period despite antirejection immunosuppressive therapy. Damage or pathogen-associated molecular pattern molecules and their associated ongoing inflammation within the transplanted organ and the recipients' intestine have been implicated as possible etiologies. Various viral, bacterial, and protozoal infections can mimic IBD in postorgan transplantation. Common IBD mimickers in the postbone marrow transplant setting are graft-versus-host disease, infectious enteritis/colitis, and less commonly "cord colitis" that is described in detail below. In this article, we discuss the epidemiology, clinical features, and outcomes of de novo IBD after transplantation and highlight their differences in presentation, diagnosis, and management.

Is the presence of 6 or fewer crypt apoptotic bodies sufficient for diagnosis of graft versus host disease? A decade of experience at a single institution

Histopathology assessment is crucial for the diagnosis of graft versus host disease (GVHD), as the presence of crypt apoptosis is the cardinal criterion required. However, crypt apoptosis is not limited to GVHD; it also occurs in other conditions such as infection, drug reaction, or inflammatory reactions unrelated to GVHD. To better determine whether the presence of 6 or fewer apoptotic bodies is sufficient for the diagnosis of GVHD, we retrospectively reviewed 78 colon biopsies from 66 patients who received either hematopoietic stem cell (HSCT) or cord blood cell transplantation and whose colon biopsies exhibited apoptotic bodies. Among them, 41 cases contained 6 or fewer apoptotic bodies in the colon biopsy. These biopsies were compared with 141 colon biopsy controls that showed no significant pathologic changes as well as 16 colon biopsies with cytomegalovirus colitis from patients without a history of bone marrow transplantation. Among the 41 cases reviewed, 7 patients had coexisting GVHD in other organs (skin or liver). However, gastrointestinal symptoms of at least 4 HSCT patients whose colon biopsies contained 6 or fewer apoptotic bodies completely resolved in the absence of further intervention for GVHD. The discrepancy between pathologic findings and the clinical course may be due to confounding factors, such as infection or medication-induced injury. Our data suggest that identifying 6 or fewer crypt apoptotic bodies in colon biopsies from HSCT patients is worth reporting in order to alert the clinicians of the possibility of GVHD but not sufficient to render a diagnosis on the pathologic grounds alone. The colon biopsies containing 6 or fewer apoptotic bodies represent a heterogenous group. We suggest this group to be classified as indeterminate for GVHD, instead of diagnosing GVHD outright. Synthesis of all clinical, endoscopic, and pathologic information, including the status of infection, coexisting GVHD involvement in the other organs, and medication, is essential for confirmation of the diagnosis of GVHD.

Drug-induced inflammatory bowel disease and IBD-like conditions

The pathogenesis of inflammatory bowel disease (IBD) is multifactorial and results from an interaction between genetic, immunologic, microbial, and environmental factors. Certain drugs could act as a trigger for the disease and have been implicated in the development of new onset IBD in a number a studies. These relationships are based on case reports and cohort studies, as proving this in the context of randomized controlled trials would be difficult. Drugs that have been linked to causing or worsening IBD include isotretinoin, antibiotics, nonsteroidal antiinflammatory drugs, oral contraceptives, mycophenolate mofetil, etanercept, ipilimumab, and rituximab. Bowel preparation for colonoscopy has also been associated with aphthoid lesions that may be confused with IBD. However, given the source of these reports we have to be cautious in the interpretation of the data before concluding that these drugs trigger IBD and what is being observed is not related to other confounding factors. Different pathogenic mechanisms have been suggested for the different drugs listed above. In order to clarify the confusion a comprehensive literature review was performed with the goal of advancing the knowledge on this subject.