Azathioprine induced nodular regenerative hyperplasia in IBD patients

Exploring the link: Porto-sinusoidal vascular disorder and inflammatory bowel disease - A comprehensive narrative review

Porto-sinusoidal vascular disorder (PSVD) encompasses a group of vascular disorders characterized by lesions involving the portal venules and sinusoids, independent of the presence of portal hypertension (PH), and for which liver biopsy is essential for diagnosis. PSVD has been shown to be common in patients with immune-mediated diseases, including inflammatory bowel disease (IBD). The association between PSVD and the use of thiopurines and thioguanine in patients with IBD has been well established. In addition, research suggests an association between PSVD and IBD, even in cases where patients haven't been exposed to specific medications, probably related to changes in intestinal permeability. The identification and management of patients with known IBD and PSVD is a challenge for gastroenterologists. This narrative review aims to summarize the currently available data on the association between IBD and PSVD and provide practical suggestions for the management of this group of patients.

A rare case of liver regenerative and non-neoplastic lesion resembling a well-differentiated hepatocellular carcinoma

BACKGROUND

Nodular regenerative hyperplasia (NRH) is a rare disease that presents pathologically as diffuse hepatic nodules without fibrous septa. It is believed to be caused by vasculopathy against a background of various systemic diseases, such as hematologic, autoimmune, and drug-induced diseases, with various symptoms. In spite of the recent imaging advances, various atypical cases of nodular lesions are observed in daily clinical practice. Cases that do not completely meet these criteria are referred to as -like or -similar lesions in clinical situations, making it difficult to understand their pathogenesis. We present a case in which two hepatic nodular lesions were noted and difficult to differentiate from malignancy preoperatively. The lesions were laparoscopically resected and a pathological diagnosis with non-neoplastic liver regenerative nodules resembling NRH was made.

CASE PRESENTATION

A 49-year-old man with no alcohol or drug intake and no past medical history was identified as having liver tumors on screening examination without any symptoms. Contrast-enhanced computed tomography (CT) showed two hepatic tumors; approximately 2-cm tumors at S7 and S8. Gadolinium-ethoxybenzyl-diethylenetriamine-pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) revealed fat inclusions in their contents. Ethoxybenzyl (EOB) uptake was also observed during the hepatobiliary phase. Based on preoperative examinations, we suspected well-differentiated hepatocellular carcinoma (HCC) and performed laparoscopic S7/8 partial resection for these lesions. Macroscopically, the resected specimens showed a non-cirrhotic yellowish-cut surface containing brownish, ill-defined lesions with irregular borders. Microscopically, these lesions showed zonal necrosis, congestion, and aggregation of hemosiderin-laden macrophages around the central vein. In these areas, the fatty deposition of hepatocytes was lower than that in the surrounding background hepatocytes. Histopathologically, neither neoplastic nor hyperplastic lesions were observed, and he was diagnosed as regenerative hepatic change with centrilobular necrosis.

CONCLUSIONS

Considering the pathological results, these lesions were thought to be a type of NRH-like lesion with possible hepatic vessel disorder. However, the lesion's cause and classification was difficult to determine. The accumulation of these regenerative changes accompanying fatty liver is needed to clarify the mechanism and its clinical significance.

The prevalence of nodular regenerative hyperplasia of the liver in long-term thiopurine-treated inflammatory bowel disease patients

INTRODUCTION

Nodular regenerative hyperplasia (NRH) has been associated with thiopurine therapy in patients with inflammatory bowel disease (IBD), but prevalence and prognosis of NRH remain unclear. This study is a cross-sectional search for NRH in IBD patients with long-term azathioprine or 6-mercaptopurine treatment.

MATERIAL AND METHODS

Thirty-three IBD patients with continuous azathioprine/6-mercaptopurine treatment for at least 5 years were included. Laboratory tests, thiopurine metabolite levels, liver histology, MRI were examined for NRH and signs of portal hypertension.

RESULTS

NRH was not observed in this cohort of 33 patients. Nevertheless, some possibly related signs of vascular changes were found by MRI in three patients. Also, splenomegaly, which may be associated with portal hypertension, was found in one patient. No high thiopurine dose neither high metabolite levels were found in these patients.

CONCLUSION

No NRH was found in this group of IBD patients with long-term azathioprine/6-mercaptopurine treatment. Larger multicenter studies are needed to determine the prevalence of NRH in thiopurine-treated IBD patients.

A case of idiopathic portal hypertension accompanying multiple hepatic nodular regenerative hyperplasia in a patient with systemic sclerosis

Idiopathic portal hypertension (IPH) is one of the background diseases causing nodular regenerative hyperplasia (NRH). Furthermore, IPH patients accompanied with autoimmune diseases, such as systemic lupus erythematosus (SLE) and systemic sclerosis (SSc), are more likely to form NRH in the liver. A 76-year-old woman had been aware of the Raynaud's phenomenon and scleroderma for the past 30 years. In this case, she presented with abdominal fullness, and her imaging analysis revealed ascites and multiple liver nodules. On Gd-EOB-DTPA enhanced magnetic resonance imaging (EOB-MRI), donut-like uptake was observed in the nodules in the hepatobiliary phase. Liver biopsy of a nodule demonstrated that it was composed of hyperplastic hepatocytes without fibrous septa, and dilated sinusoids were observed beside the nodule. Conversely, background liver showed that peripheral portal veins appeared stenotic with dense fibrosis in the portal area. The final diagnosis was that multiple NRH of the liver developed in SSc patient accompanying IPH. This case suggests that NRH may be unexpectedly diagnosed in patients with autoimmune diseases accompanying IPH.

Limited relevance and progression of histological alterations in the liver during thioguanine therapy in inflammatory bowel disease patients

Background: Thioguanine is associated with liver toxicity, especially nodular regenerative hyperplasia (NRH). We assessed if liver histology alters during long-term maintenance treatment with thioguanine in patients with inflammatory bowel disease (IBD). Methods: Liver specimens of thioguanine treated IBD patients with at least two liver biopsies were revised by two independent liver pathologists, blinded to clinical characteristics. Alterations in histopathological findings between first and sequential liver specimen were evaluated and associated clinical data, including laboratory parameters and abdominal imaging reports, were collected. Results: Twenty-five IBD patients underwent sequential liver biopsies prior to, at time of, or after cessation of thioguanine treatment. The median time between the first and second biopsy was 25 months (range: 14-54). Except for one normal liver specimen, any degree of irregularities including inflammation, steatosis, fibrosis and some vascular disturbances were observed in the biopsies. The rates of perisinusoidal fibrosis (91%), sinusoidal dilatation (68%) and nodularity (18%) were the same in the first and second liver biopsies. A trend towards statistical significance was observed for phlebosclerosis (36% of the first vs. 68% of the second biopsies, p = .092). Presence of histopathological liver abnormalities was not associated with clinical outcomes. Furthermore, two patients in this cohort had portal hypertension in presence of phlebosclerosis. In another two patients, nodularity of the liver resolved upon thioguanine withdrawal. Conclusion: Vascular abnormalities of the liver were commonly observed in thioguanine treated IBD patients, although these were not progressive and remained of limited clinical relevance over time.

Chronic liver injury induced by drugs and toxins

Drug-induced liver injury (DILI) occurs in a small fraction of individuals exposed to drugs, herbs or dietary supplements and is a relatively rare diagnosis compared with other liver disorders. DILI can be serious, resulting in hospitalization and even life-threatening liver failure, death or need for liver transplantation. Toxic liver damage usually presents as an acute hepatitis viral-like syndrome or as an acute cholestasis that resolves upon drug discontinuation. However, un-resolving chronic outcome after acute DILI can ensue in some subjects, the mechanisms and risk factors for this particular evolution being yet scarcely known. Furthermore, the definition of chronicity after acute DILI is controversial, regarding both the time frame of liver injury persistence and the magnitude of the abnormalities required. Besides this, in some instances the phenotypes and pathological manifestations are those of chronic liver disease at the time of DILI diagnosis. These include non-alcoholic fatty liver disease, vascular lesions, drug-induced autoimmune hepatitis, chronic cholestasis leading to vanishing bile duct syndrome and even cirrhosis, and some drugs such as amiodarone or methotrexate have been frequently implicated in some of these forms of chronic DILI. In addition, all of these DILI phenotypes can be indistinguishable from those related to other etiologies, making the diagnosis particularly challenging. In this manuscript we have critically reviewed the more recent data on chronicity in DILI with a particular focus on the epidemiology, mechanisms and risk factors of atypical chronic DILI phenotypes.

Clinical and histologic features of Azathioprine-induced hepatotoxicity

BACKGROUND

Hepatoxicity is a relative uncommon complication related with Azathioprine, however most studies were performed in inflammatory bowel diseases patients. The aim of this study is to report the clinical profile of patients with Azathioprine-induced hepatotoxicity.

METHODS

All medical records of patients received Azathioprine from 2010 to 2015 were retrospectively reviewed. Hepatotoxicity was defined as serum alanine aminotransferase (ALT) or aspatate aminotransferase (AST) or total bilirubin >2 times upper limit normal. Other causes of liver diseases were excluded. All subjects were followed until the resolution of liver injury.

RESULTS

Two-hundred and ninety-three patients receiving Azathioprine were retrospectively reviewed. Eight patients (2.7%) were diagnosed with Azathioprine-induced hepatotoxicity. The median age was 45 year with female preponderance. The latency to onset of liver injury ranged from 7 to 236 d, and 4 patients were symptomatic. Median peak levels were ALT 295 U/L, alkaline phosphatase 169 U/L, and total bilirubin 1 mg/dl. According to R-ratio, mixed pattern (50%) was more frequent than cholestatic (37.5%) and hepatocellular pattern (12.5%). Liver biopsies were performed in 2 patients, and showed hepatocellular and canalicular cholestasis with mild portal and peri-portal inflammation. All patients recovered fully with a median time of 41.3 days. Two patients developed prolonged cholestasis >2 months, hence none had liver failure or required liver transplantation.

CONCLUSION

Hepatotoxicity is relative uncommon in patients receiving Azathioprine, and predominantly is mixed hepatocellular and cholestatic in nature. Even though all patients recover fully after drug withdrawal, severe cholestasis can occur.

A case of nodular regenerative hyperplasia of the liver combined with toxic hepatitis

Nodular regenerative hyperplasia (NRH) is an uncommon liver condition characterized by diffuse transformation of the hepatic parenchyma into regenerative nodules without fibrosis. Portal vasculopathy caused by abnormal hepatic venous flow may induce hepatocyte hyperplasia, which forms regenerative nodules. Underlying diseases or certain drugs may also be the cause of NRH. This condition is often underdiagnosed as the patients remain asymptomatic until development of portal hypertension, and histopathologic confirmation by liver biopsy is the only way of making a definite diagnosis. The management mainly involves prevention and treatment of the complications of portal hypertension. The frequency of diagnosis of NRH has increased rapidly in recent years, however, only a few cases have been reported in Korea. Here, we report on a case of NRH of the liver combined with toxic hepatitis.

Chronic liver injury induced by drugs: a systematic review

To examine the available literature and summarize what is known about chronic drug-induced liver injury. We reviewed PubMed/MEDLINE through March 2015. We developed a MEDLINE search strategy using PubMed medical subject heading terms chronic liver injury, hepatotoxicity, drug-induced liver injury, cirrhosis and chronic liver disease. We reviewed the reference list of included articles to identify articles missed in the database search. Chronic liver injury from drugs is more common than once thought with prevalence as high as 18% based on large national registries. Patients with cholestatic injury, age ≤65 years, and a long latency period (>365 days) are at increased risk. Of the most common drugs associated with drug-induced liver injury, antibiotics (amoxicillin-clavulanic acid, trimethoprim-sulfamethoxazole, azithromycin) are most likely to cause chronic injury. The presence of autoantibodies is common with chronic DILI, however, it is not diagnostic nor is it specific to autoimmune-like drug-induced liver injury. Immunosuppressive therapy may be necessary for individual cases of autoimmune-like drug-induced liver injury where cessation of the drug alone does not result in resolution of injury, however, the lowest dose should be used for the shortest duration with careful attention to the development of side effects. The effectiveness of treament of cholestatic liver injury with corticosteroids or ursodiol remains unclear. Cases of drug-induced fatty liver, nodular regenerative hyperplasia and peliosis hepatitis are less common subtypes of chronic drug-induced liver injury that deserve special consideration. A high degree of clinical suspicion is required for the diagnosis of chronic drug-induced liver injury and should be suspected in any patient with liver associated enzyme abnormalities that persist out past 6 months of initial presentation. Treatment with drug removal and/or immunosuppressive therapy appears to be effective for the majority of cases. More study into pharmacogenomics and personalized medicine may aid in predicting which patients will go on to develop chronic drug-induced liver injury.

Azathioprine-induced hepatitis and cholestasis occurring 1 year after treatment

Azathioprine is an immunosuppressive medication used in the management of many autoimmune conditions. Commonly reported adverse effects from azathioprine therapy are nausea and bone marrow suppression, while less common side effects include hepatotoxicity. We present the case of a 47-year-old man with a history of myasthenia gravis on azathioprine for 1 year, who presented to our institution with painless jaundice. On initial laboratory evaluation, the level of aspartate aminotransferase, alanine aminotransferase and total bilirubin were markedly elevated. Owing to the potential diagnosis of acute liver failure secondary to azathioprine toxicity, this medication was discontinued. A liver biopsy demonstrating drug-induced liver injury, along with high serum levels of 6-methylmercaptopurine nucleotide confirmed the diagnosis of azathioprine-induced hepatotoxicity. Upon discontinuation of the medication, the patient's transaminases and bilirubin levels improved steadily over the four-day hospital course. This case emphasises azathioprine's potential for hepatotoxicity, even 1 year after the initiation of its use.

The liver in pediatric gastrointestinal disease

Hepatic involvement is often encountered in gastrointestinal (GI) diseases, in part because of the close anatomic and physiologic relations between the liver and GI tract. Drainage of the mesenteric blood supply to the portal vein permits absorbed and/or translocated nutrients, toxins, bacterial elements, cytokines, and immunocytes to gain hepatic access. Liver problems in digestive disorders may range from nonspecific hepatocellular enzyme elevations to significant pathologic processes that may progress to end-stage liver disease. Hepatobiliary manifestations of primary GI diseases in childhood and adolescence are not uncommon and include several well-described associations, such as sclerosing cholangitis with inflammatory bowel disease. Liver damage may also result from the effects of drugs used to treat GI diseases, for example, the hepatotoxicity of immunomodulatory therapies. This review highlights the important features of the hepatic and biliary abnormalities associated with 3 common pediatric GI conditions: inflammatory bowel disease, celiac disease, and cystic fibrosis.

Evaluation of azathioprine-induced cytotoxicity in an in vitro rat hepatocyte system

Azathioprine (AZA) is widely used in clinical practice for preventing graft rejection in organ transplantations and various autoimmune and dermatological diseases with documented unpredictable hepatotoxicity. The potential molecular cytotoxic mechanisms of AZA towards isolated rat hepatocytes were investigated in this study using “Accelerated Cytotoxicity Mechanism Screening” techniques. The concentration of AZA required to cause 50% cytotoxicity in 2 hrs at 37°C was found to be 400 μM. A significant increase in AZA-induced cytotoxicity and reactive oxygen species (ROS) formation was observed when glutathione- (GSH-) depleted hepatocytes were used. The addition of N-acetylcysteine decreased cytotoxicity and ROS formation. Xanthine oxidase inhibition by allopurinol decreased AZA-induced cytotoxicity, ROS, and hydrogen peroxide (H₂O₂) formation and increased % mitochondrial membrane potential (MMP). Addition of N-acetylcysteine and allopurinol together caused nearly complete cytoprotection against AZA-induced hepatocyte death. TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl), a known ROS scavenger and a superoxide dismutase mimic, and antioxidants, like DPPD (N,N′-diphenyl-p-phenylenediamine), Trolox (a water soluble vitamin E analogue), and mesna (2-mercaptoethanesulfonate), also decreased hepatocyte death and ROS formation. Results from this study suggest that AZA-induced cytotoxicity in isolated rat hepatocytes may be partly due to ROS formation and GSH depletion that resulted in oxidative stress and mitochondrial injury.

Review article: the association between nodular regenerative hyperplasia, inflammatory bowel disease and thiopurine therapy

BACKGROUND

Nodular regenerative hyperplasia (NRH) is increasingly being recognised in patients with inflammatory bowel disease (IBD). However, the pathogenesis and incidence of NRH in IBD, and the putative roles played by azathioprine (AZA), mercaptopurine (MP), or tioguanine (TG) remain unclear.

AIMS

To summarise the data on the association between NRH and thiopurine therapy in patients with IBD.

METHODS

A literature search was performed in PubMed and MEDLINE databases using the keywords 'nodular regenerative hyperplasia AND (inflammatory bowel disease OR Crohn's disease OR ulcerative colitis) AND (azathioprine OR mercaptopurine OR tioguanine OR thioguanine).' No time limit was placed on studies included.

RESULTS

Inflammatory bowel disease patients treated with AZA have a cumulative incidence of NRH of approximately 0.6% and 1.28% at 5 and 10 years, respectively, whereas those treated with high-dose TG (>40 mg/day) have a frequency of NRH of up to 62%, which is higher in patients with elevated liver enzymes and/or thrombocytopaenia than those without these abnormalities (frequency 76% vs. 33%). Conversely, low-dose TG therapy (<20 mg/day) is relatively safe, with no cases of NRH observed. NRH has also been found in 6% of operated thiopurine-naïve IBD patients. Male gender, older age, and stricturing disease/small bowel resection have been consistently identified as high-risk factors for NRH.

CONCLUSIONS

The pathogenesis of nodular regenerative hyperplasia in patients with IBD is complex and multifactorial involving disease-specific, genetic and iatrogenic risk factors. Clinicians should maintain a high index of suspicion for diagnosing nodular regenerative hyperplasia, especially in IBD patients with high-risk factors on thiopurine therapy, regardless of the presence of laboratory abnormalities.

Thiopurines in inflammatory bowel disease revisited

Although a great variety of new drugs have been introduced for the therapy of inflammatory bowel diseases so far, a definite cure of the disease is still out of scope. An anti-inflammatory approach to induce remission followed by maintenance therapy with immunosupressants is still the mainstay of therapy. Thiopurines comprising azathioprine and its active metabolite mercaptopurine as well as tioguanine, are widely used in the therapy of chronic active inflammatory bowel disease (IBD). Their steroid sparing potential and efficacy in remission maintenance are out of doubt. Unfortunately, untoward adverse events are frequently observed and may preclude further administration or be life threatening. This review will focus on new aspects of thiopurine therapy in IBD, its efficacy and safety.

Clinical analysis of 15 cases of liver nodular regenerative hyperplasia

Nodular regenerative hyperplasia (NRH) of liver may be one of the leading causes of non-cirrhotic intrahepatic portal hypertension (NCIPH), although the exact relationship is currently unknown. Diagnosis of NRH is relatively difficult and involves surgical pathology, and thus it is necessary to improve the preoperative recognition of NRH. Here, we analyze 15 cases of NRH to better understand this disease. All the liver specimens were microscopically examined by hematoxylin-eosin staining and reticulin and Masson trichrome staining. Diagnoses of NRH were confirmed by pathological examination. Clinically, NRH presents as diffused liver lesions with mildly increased liver enzymes. Portal hypertension is the most common clinical manifestation presenting prominently as splenomegaly, hypersplenism, and esophageal varices bleeding. NRH is often associated with autoimmune or collagen vascular diseases, and such patients often present with a variety of positive autoantibodies and increased erythrocyte sedimentation rate (ESR), Ig and γ %. Pathological examination of the liver showed diffuse small regenerative nodules without fibrous septa and obstructive portal venopathy. For those patients with portal hypertension of unknown cause and preserved liver function, especially, those combined with autoimmune diseases, NRH should be considered.

Hepatic hemodynamics in 24 patients with nodular regenerative hyperplasia and symptomatic portal hypertension

BACKGROUND AND AIM

To evaluate hepatic hemodynamics in patients with nodular regenerative hyperplasia of the liver (NRH) with portal hypertension (PHT).

METHODS

We retrospectively reviewed the charts of 24 patients referred for PHT related to biopsy-proven NRH. Hemodynamic measurements included wedged hepatic vein (WHVP) and inferior vena cava (IVCP), and, in 12 patients, portal vein pressure (PVP). Hepatic vein pressure gradient (HVPG: WHVP-IVCP) and portal vein pressure gradient (PVPG: PVP-IVCP) were calculated.

RESULTS

Nodular regenerative hyperplasia was associated in 24 patients with various diseases (oxaliplatin chemotherapy, treatment with purine antagonists, post liver transplantation, hematologic and rheumatologic conditions and HIV infection). Liver function parameters were either completely normal or slightly impaired. Patients were referred for gastroesophageal varices (n = 18), and/or ascites (n = 11), and/or splenomegaly (n = 20). In patients with varices or ascites, HVPG was lower than 10 mmHg (a cut-off point for the presence of varices and/or ascites) in 15/21, suggesting a pre-sinusoidal component to their PHT confirmed by a PVP higher than 12 mmHg in 12/12 patients. The mean difference between HVPG and PVPG was 8.7 mmHg in these patients. Ten patients were treated by transjugular intrahepatic portosystemic shunt. None of them re-bled, and one presented transient hepatic encephalopathy.

CONCLUSIONS

Presinusoidal PHT associated with NRH is probably related to compression of portal venules by the regenerative nodules. In patients with HTP and a HVPG < 10 mmHg, the diagnosis of NRH must be suspected and PVP measured, which is important in the management of these patients.

A Histopathologic Pattern of Centrilobular Hepatocyte Injury Suggests 6-Mercaptopurine-Induced Hepatotoxicity in Patients With Inflammatory Bowel Disease

Context.—Hepatotoxicity is an important side effect of thiopurine analog treatment for inflammatory bowel disease. A variety of histopathologic findings have been observed in patients with inflammatory bowel disease with thiopurine-induced hepatotoxicity, including nodular regenerative hyperplasia, vascular injury, and cholestasis.

Objective.—To describe the histologic features shared by 3 cases of thiopurine-induced hepatotoxicity in patients with inflammatory bowel disease.

Design.—We identified 3 patients with inflammatory bowel disease who developed hepatotoxicity due to 6-mercaptopurine from the educational files of the Department of Pathology at Massachusetts General Hospital (Boston). Histology slides (stained with hematoxylin-eosin, trichrome, periodic-acid Schiff with diastase digestion, and iron stains) and patients' medical records were reviewed retrospectively.

Results.—All 3 patients were receiving 6-mercaptopurine monotherapy at therapeutic doses, had normal thiopurine metabolite levels, and presented with elevated aminotransferase levels. Biopsies from all 3 cases exhibited a pattern of centrilobular hepatocyte injury characterized by ceroid-laden macrophages, hepatocyte anisonucleosis, and increased lipofuscin pigment, as well as centrilobular steatosis. Aminotransferase levels trended downward and either normalized or remained at borderline elevated levels after 6-mercaptopurine dose was reduced (in 1 patient) or discontinued (in 2 patients).

Conclusions.—Recognition of a pattern of centrilobular injury enables pathologists to suggest thiopurine-induced liver injury as the cause of elevated aminotransferases in patients with inflammatory bowel disease.

Liver disorders in inflammatory bowel disease

Disorders of the hepatobiliary system are relatively common extraintestinal manifestations of inflammatory bowel disease (IBD). These disorders are sometimes due to a shared pathogenesis with IBD as seen in primary sclerosing cholangitis (PSC) and small-duct primary sclerosing cholangitis (small-duct PSC). There are also hepatobiliary manifestations such as cholelithiasis and portal vein thrombosis that occur due to the effects of chronic inflammation and the severity of bowel disease. Lastly, medications used in IBD such as sulfasalazine, thiopurines, and methotrexate can adversely affect the liver. It is important to be cognizant of these disorders as some do have serious long-term consequences. The management of these disorders often requires the expertise of multidisciplinary teams to achieve the best outcomes.

Review article: the benefits of pharmacogenetics for improving thiopurine therapy in inflammatory bowel disease

BACKGROUND

Thiopurines represent an effective and widely prescribed therapy in inflammatory bowel disease (IBD). Concerns about toxicity, mainly resulting from a wide inter-individual variability in thiopurine metabolism, restrict their use. Optimal thiopurine dosing is challenging for preventing adverse drug reactions and improving clinical response.

AIM

To review efficacy and toxicity of thiopurines in IBD. To provide pharmacogenetic-based therapeutic recommendations.

METHODS

We conducted a query on PubMed database using 'inflammatory bowel disease', 'thiopurine', 'azathioprine', '6-mercaptopurine', 'TPMT', 'pharmacogenetics', 'TDM', and selected relevant articles, especially clinical studies.

RESULTS

Thiopurine metabolism - key enzyme: thiopurine S-methyltransferase (TPMT) - modulates clinical response, as it results in production of the pharmacologically active and toxic metabolites, the thioguanine nucleotides (6-TGN). Adjusting dosage according to TPMT status and/or metabolite blood levels is recommended for optimising thiopurine therapy (e.g. improving response rate up to 30% or decreasing haematological adverse events of 25%). Other enzymes or transporters of interest, as inosine triphosphatase (ITPase), glutathione S-transferase (GST), xanthine oxidase (XO), aldehyde oxidase (AOX), methylene tetrahydrofolate reductase (MTHFR) and ATP-binding cassette sub-family C member 4 (ABCC4) are reviewed and discussed for clinical relevance.

CONCLUSIONS

Based on the literature data, we provide a therapeutic algorithm for thiopurines therapy with starting dose recommendations depending on TPMT status and thereafter dose adjustments according to five metabolite profiles identified with therapeutic drug monitoring (TDM). This algorithm allows a dosage individualisation to optimise the management of patients under thiopurine. Furthermore, identification of new pharmacogenetic biomarkers is promising for ensuring maximal therapeutic response to thiopurines with a minimisation of the risk for adverse events.

Biologic and clinical features of benign solid and cystic lesions of the liver

The widespread use of imaging analyses, either routinely or to evaluate symptomatic patients, has increased the detection of liver lesions (tumors and cysts) in otherwise healthy individuals. Although some of these incidentally discovered masses are malignant, most are benign and must be included in the differential diagnosis. The management of benign hepatic tumors ranges from conservative to aggressive, depending on the nature of the lesions. New imaging modalities, increased experience of radiologists, improved definition of radiologic characteristics, and a better understanding of the clinical features of these lesions have increased the accuracy of diagnoses and reduced the need for invasive diagnostic tests. These advances have led to constant adjustments in management approaches to benign hepatic lesions. We review the biologic and clinical features of some common hepatic lesions, to guide diagnosis and management strategies.

Nodular regenerative hyperplasia: Evolving concepts on underdiagnosed cause of portal hypertension

Nodular regenerative hyperplasia (NRH) is a rare liver condition characterized by a widespread benign transformation of the hepatic parenchyma into small regenerative nodules. NRH may lead to the development of non-cirrhotic portal hypertension. There are no published systematic population studies on NRH and our current knowledge is limited to case reports and case series. NRH may develop via autoimmune, hematological, infectious, neoplastic, or drug-related causes. The disease is usually asymptomatic, slowly or non-progressive unless complications of portal hypertension develop. Accurate diagnosis is made by histopathology, which demonstrates diffuse micronodular transformation without fibrous septa. Lack of perinuclear collagen tissue distinguishes NRH from typical regenerative nodules in the cirrhotic liver. While the initial treatment is to address the underlying disease, ultimately the therapy is directed to the management of portal hypertension. The prognosis of NRH depends on both the severity of the underlying illness and the prevention of secondary complications of portal hypertension. In this review we detail the epidemiology, pathogenesis, diagnosis, management, and prognosis of NRH.

The role of nucleoside and nucleotide analogues in nodular regenerative hyperplasia in HIV-infected patients: a case control study

BACKGROUND & AIMS

Nodular regenerative hyperplasia (NRH) leading to non-cirrhotic portal hypertension has been described in HIV-infected patients and has been linked to didanosine. The relation between NRH and other antiretrovirals remains unclear.

METHODS

A case-control study was performed in 13 patients with NRH and 78 controls matched for time of inclusion, baseline CD4, and duration of follow-up. Univariate and multivariate conditional logistic regression analyses were performed.

RESULTS

Control patients and patients with NRH were similar at baseline regarding demographics and biological data with the exception of older age for patients with NRH (43.9 vs. 33.5 years, p=0.044). At the time of NRH diagnosis, cases had a lower CD4 count (327 vs. 468/mm(3), p=0.013), a similar CD4 percentage (24 vs. 26.2%, p=0.7), a lower platelet count (169 vs. 228 giga/L, p=0.003) and a higher AST level (33 vs. 26 IU/L, p=0.001) than controls. Univariate analysis demonstrated that patients with NRH had been exposed longer than controls to didanosine, stavudine, tenofovir, didanosine+stavudine, and didanosine+tenofovir. The age at baseline [OR 2.2 (1.0-5.0) per 10 years, p=0.053] and didanosine+stavudine cumulative exposure [OR 3.7 (1.4-10.2) per year, p=0.011] were independently associated with NRH. The age at baseline [OR 2.3 (1.0-5.3) per 10 years, p=0.045], cumulative exposure to didanosine [OR 1.4 (1.1-1.9) per year, p=0.023] and to tenofovir [OR 1.7 (1.0-2.8) per year, p=0.04] were independently associated with NRH when didanosine+stavudine exposure was excluded from the model.

CONCLUSIONS

NRH in HIV-infected patients seems strongly related to age and the cumulative exposure to didanosine+stavudine, didanosine, and stavudine.

Incidence of nodular regenerative hyperplasia in inflammatory bowel disease patients treated with azathioprine

BACKGROUND

Nodular regenerative hyperplasia (NRH) is a rare hepatic disorder that may lead to severe portal hypertension. Cases of NRH have been reported in patients receiving thiopurines for inflammatory bowel disease (IBD). Since azathioprine (AZA) is used more and more frequently as a maintenance treatment in IBD, the risk of NRH must be known. The objective of this study was to evaluate the prevalence of NRH and its predictive factors in IBD patients treated with AZA.

MATERIALS AND METHODS

From the same tertiary referral center, 1888 consecutive IBD patients treated with AZA were studied. Clinical diagnosis of NRH was proven by liver biopsy in all cases except one. The cumulative risk of NRH was estimated with the Kaplan-Meier method. Factors associated with NRH were tested independently with the log-rank method and multivariate proportional hazards model with time-dependent covariates.

RESULTS

Fifteen patients developed NRH in a median treatment duration of 52.4 months (SE 1.6). The cumulative incidence of NRH was 1.28±0.45% at 10 years. Only two variables were independently associated with NRH occurrence: male gender (P=0.0001, hazard ratio [HR] 8.5, 95% confidence interval [CI] 1.9-37.9) and small bowel resection≥50 cm (P<0.0001, HR 6.6, 95% CI 2.2-20.0), either prior to or after AZA initiation.

CONCLUSIONS

The risk of developing NRH during AZA treatment is low. This study suggests that male patients with small bowel resection≥50 cm constitute the group with the higher risk of developing NRH while treated with AZA.

Assessment of non-cirrhotic portal hypertension associated with thiopurine therapy in inflammatory bowel disease

Thiopurines represent an effective and widely used immunosuppressant in the therapeutic armamentarium of inflammatory bowel disease. However up to 25% of patients may be unable to continue the drug due to side effects. The incidence of hepatotoxicity associated with thiopurine use is reported between 0% and 32%. Veno-occlusive disease, peliosis hepatis, perisinusoidal fibrosis and nodular regenerative hyperplasia have all been described with thiopurines. Recent trials of 6-tioguanine, although successful in patients with allergies to azathioprine or mercaptopurine, have been compromised by increased hepatotoxicity, either veno-occlusive disease or nodular regenerative hyperplasia. We describe a report of nodular regenerative hyperplasia in a Crohn's disease patient associated with 6-mercaptopurine therapy and have reviewed the management and the literature regarding this complication. Our report strengthens the importance of further safety studies to evaluate the etiology, prevalence, risk factors and screening modalities for hepatotoxicity, in particular of nodular regenerative hyperplasia, in patients treated with thiopurines for inflammatory bowel disease.

Non-cirrhotic intrahepatic portal hypertension: associated gut diseases and prognostic factors

BACKGROUND/AIMS

Non-cirrhotic intrahepatic portal hypertension (NCIPH) is generally regarded to have a benign prognosis. We have studied a cohort followed-up at a tertiary referral center and postulate that gut-derived prothrombotic factors may contribute to the pathogenesis and prognosis of NCIPH.

METHODS

We retrospectively analyzed prognostic indicators in 34 NCIPH patients. We also searched for associated gut diseases.

RESULTS

Transplant-free survival in NCIPH patients from first presentation with NCIPH at 1, 5, and 10 years was 94% (SE: 4.2%), 84% (6.6%), and 69% (9.8%), respectively. Decompensated liver disease occurred in 53% of patients. Three (9%) patients had ulcerative colitis while five of 31 (16%) tested had celiac disease and on Kaplan-Meier analysis, celiac disease predicted reduced transplant-free survival (p=0.018). On multivariable Cox regression analysis, independent predictors of reduced transplant-free survival were older age at first presentation with NCIPH, hepatic encephalopathy, and portal vein thrombosis. Prevalence of elevated initial serum IgA anticardiolipin antibody (CLPA) was significantly higher in NCIPH (36% of patients tested), compared to Budd-Chiari syndrome (6%) (p=0.032, Fisher's exact test) and celiac disease without concomitant liver disease (0%) (p=0.007).

CONCLUSIONS

We have identified prognostic factors and report progression to liver failure in 53% of NCIPH patients followed-up at our center. Our data supports a role for intestinal disease in the pathogenesis of intrahepatic portal vein occlusion leading to NCIPH.

Prevalence and risk factors for abnormal liver stiffness in HIV-infected patients without viral hepatitis coinfection: role of didanosine

BACKGROUND

Unexpected cases of severe liver disease in HIV-infected patients have been reported and an association with didanosine (ddI) has been suggested. Transient elastography (TE) might detect patients harbouring such a condition. Our objective was to search for the presence of abnormal liver stiffness (LS) in a cohort of HIV-infected patients without HBV or HCV coinfection and to assess the related factors.

METHODS

A cross-sectional prospective study was conducted. LS was assessed by TE in 258 HIV-infected patients without HBV or HCV coinfection and with no evidence of acute hepatotoxicity or other origins of liver disease. LS values > or =7.2 kPa were considered abnormal. Multivariate analyses were performed to identify factors associated with abnormal LS.

RESULTS

Abnormal LS was observed in 29 (11.2%) patients. A total of 18 (16.4%) patients previously treated with ddI and 11 (7.4%) of those who never received ddI had LS values > or =7.2 kPa (P=0.02). The prevalence of abnormal LS was higher in patients previously treated with abacavir than in those who had never received abacavir (15 [21.7%] versus 14 [7.4%]; P=0.001). After multivariate analyses, age (adjusted odds ratio [AOR] 1.05, 95% confidence interval [CI] 1.002-1.1; P=0.004) alcohol intake >50 g/day (AOR 7.2, 95% CI 2.6-19.7; P<0.0001), CD4(+) T-cell count <200 cells/ml (AOR 3.4, 95% CI 1.06-11.007; P=0.03), time on ddI treatment (AOR 1.31, 95% CI 1.12-1.52; P=0.001) and previous abacavir exposure (AOR 3.01, 95% CI 1.18-7.67; P=0.02) were independently associated with abnormal LS.

CONCLUSIONS

The prevalence of abnormal LS in HIV-infected patients without HBV or HCV coinfection is substantial. Long-term exposure to ddI is a major cause of liver damage in these patients.

Hepatopancreatobiliary manifestations and complications associated with inflammatory bowel disease

Diseases involving the hepatopancreatobiliary (HPB) system are frequently encountered in patients with inflammatory bowel disease (IBD). Hepatobiliary manifestations constitute some of the most common extraintestinal manifestations of IBD. They appear to occur with similar frequency in patients with Crohn's disease or ulcerative colitis. HPB manifestations may occur in following settings: 1) disease possibly associated with a shared pathogenetic mechanism with IBD including primary sclerosing cholangitis (PSC), small-duct PSC/pericholangitis and PSC/autoimmune hepatitis overlap, acute and chronic pancreatitis related to IBD; 2) diseases which parallel structural and physiological changes seen with IBD, including cholelithiasis, portal vein thrombosis, and hepatic abscess; and 3) diseases related to adverse effects associated with treatment of IBD, including drug-induced hepatitis, pancreatitis (purine-based agents), or liver cirrhosis (methotrexate), and reactivation of hepatitis B, and biologic agent-associated hepatosplenic lymphoma. Less common HPB manifestations that have been described in association with IBD include autoimmune pancreatitis (AIP), IgG4-associated cholangitis (IAC), primary biliary cirrhosis (PBC), fatty liver, granulomatous hepatitis, and amyloidosis. PSC is the most significant hepatobiliary manifestation associated with IBD and poses substantial challenges in management requiring a multidisciplinary approach. The natural disease course of PSC may progress to cirrhosis and ultimately require liver transplantation in spite of total proctocolectomy with ileal-pouch anal anastomosis. The association between AIP, IAC, and elevated serum IgG4 in patients with PSC is intriguing. The recently reported association between IAC and IBD may open the door to investigate these complex disorders. Further studies are warranted to help understand the pathogenesis of HPB manifestations associated with IBD, which would help clinicians better manage these patients. An interdisciplinary approach, involving gastroenterologists, hepatologists, and, in advanced cases, general, colorectal, and transplant surgeons is advocated.

Nodular regenerative hyperplasia of the liver

Nodular regenerative hyperplasia (NRH), characterized by diffuse hepatic micronodular transformation in groups without fibrous septa between the nodules, is a rare benign liver lesion that has many synonyms in previous literature. Pathologic evaluation is the mainstay of accurate diagnosis. Treatment is focused on its underlying conditions and complications of portal hypertension. A 39-year-old man visited our hospital due to right upper quadrant pain and a palpable liver mass. Magnetic resonance examination revealed a slightly hyperintense tumor on T2-weighted images, and focal nodular hyperplasia was diagnosed by the radiologists. Atypical radiologic findings could not yield an accurate diagnosis. Surgical intervention was therefore performed. Pathologic examination of the resected liver tumor confirmed the diagnosis of NRH. We conclude that NRH should be included in the differential diagnosis of benign liver tumor.

Histopathology of liver biopsies from a thiopurine-naïve inflammatory bowel disease cohort: prevalence of nodular regenerative hyperplasia

OBJECTIVE

Nodular regenerative hyperplasia (NRH) and sinusoidal dilatation have been described in relation to thiopurine use in patients with inflammatory bowel disease (IBD). However, there is a dearth of data on the prevalence of these histological abnormalities in general. The aim of our study was to describe the prevalence of these histological liver changes in a thiopurine-naïve IBD cohort.

MATERIAL AND METHODS

Liver biopsy specimens were obtained from patients who were treated in a referral center and who underwent gastrointestinal surgery for IBD. Patients were excluded if thiopurines were ever used. The liver specimens were pathohistologically assessed with special attention to NRH.

RESULTS

A total of 83, properly stained, liver specimens (Crohn's disease 61%) were evaluated. NRH was observed in 6% compared to sinusoidal dilatation of varying degree in 34% of specimens. An older age at biopsy was correlated with NRH (p=0.015). Fibrosis and steatosis of varying degrees were detected in 31% and 36% of liver biopsies, respectively. No cases of liver cirrhosis were observed.

CONCLUSIONS

Pathohistological hepatic abnormalities are common in non-thiopurine using IBD patients. The association between thiopurine use, NRH and sinusoidal dilatation may be weaker than as reported in recent literature, as there is relatively high background prevalence in selected series.

Use of allopurinol with low-dose 6-mercaptopurine in inflammatory bowel disease to achieve optimal active metabolite levels: a review of four cases and the literature

BACKGROUND

At least one-third of patients with inflammatory bowel disease do not respond or are intolerant to therapy with 6-mercaptopurine (6-MP). A subgroup fails to attain optimal levels of 6-thioguanine nucleotide (6-TGN) and instead shunts to 6-methylmercaptopurine nucleotide (6-MMPN).

PATIENTS AND METHODS

A retrospective chart review was conducted, and four patients are described who had been previously unable to achieve optimal 6-TGN metabolite levels until allopurinol was added to their treatment.

RESULTS

All four patients achieved optimal 6-TGN levels and undetectable 6-MMPN with a mean 6-MP dose of 0.49 mg/kg. Three achieved steroid-free clinical remission. Two of those three patients had normalization of liver enzymes; one patient had baseline normal liver enzymes despite an initial 6-MMPN level of 27,369 pmol/8 x 10(8) red blood cells. Two patients experienced reversible leukopenia.

CONCLUSIONS

Combination allopurinol and low-dose 6-MP is an effective means to achieve optimal metabolite levels and steroid-free clinical remission in previously refractory patients. Caution is advised.

Thiopurine-methyltransferase and inosine triphosphate pyrophosphatase polymorphism in a liver transplant recipient developing nodular regenerative hyperplasia on low-dose azathioprine

The enzymes thiopurine-methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) are involved in thiopurine metabolism. We describe a liver transplant recipient who presented with liver enzyme abnormalities after 78 months of low-dose azathioprine (AZA) therapy (less than 1 mg/kg). No underlying etiology of these abnormalities was identified after extensive analysis including repeated liver biopsy. Fifteen years after transplantation, the patient presented with variceal bleeding, liver biopsy showed nodular regenerative hyperplasia (NRH). TPMT*3C genotype was found in the patient's lymphocytes and heterozygous ITPA (94C>A) genotype was found in both patient and donor liver. These findings further emphasize the importance of pharmacogenetics in predicting NRH and other adverse events during AZA therapy. Furthermore, a high index of suspicion with early detection of NRH is crucial, as improvement seems only to occur in patients with compensated liver disease. Liver biopsy and discontinuation of AZA are recommended in case of liver enzyme abnormalities or signs of portal hypertension.

Antiretroviral-Associated Portal Hypertension: A New Clinical Condition? Prevalence, Predictors and Outcome

Background

Cases of severe unexplained liver disease in HIV-infected individuals have recently been reported and are often associated with exposure to didanosine (ddI) and nodular regenerative hyperplasia. Herein, we examine the clinical outcome following ddI removal.

Methods

From 3,300 HIV-infected patients attending three clinics since 2004, all who exhibited persistently elevated aminotransferases and/or significant liver fibrosis in the absence of any known cause of liver damage were identified.

Results

Thirty-two individuals (prevalence ∼1%) met the inclusion criteria - all were on antiretroviral therapy. Of these, 84% were male and 68% had acquired HIV through homosexual contact. Liver biopsy was performed in 12, of whom three showed nonspecific advanced liver fibrosis, two nodular regenerative hyperplasia and three showed only periportal fibrosis. On follow up, nine patients developed episodes of hepatic decompensation, mainly as a consequence of portal hypertension; in eight cases (25%) portal thrombosis was diagnosed. No association was found with plasma HIV RNA or CD4+ T-cell count. All patients but three had been exposed to ddI for a median of 44 months; removal of ddI in 27 was followed 12 months later by improvement in clinical and laboratory parameters in 13 (48%) patients. Finally, a trend towards liver fibrosis improvement was recognised using FibroScan®.

Conclusions

Idiopathic persistent liver enzyme elevations in HIV-infected individuals are often associated with cirrhotic and non-cirrhotic portal hypertension. Although this is a relatively rare condition, prolonged exposure to ddI seems to play a pathogenic role and removal of the drug is associated with clinical and laboratory improvements.

6-thioguanine associated nodular regenerative hyperplasia in patients with inflammatory bowel disease may induce portal hypertension

BACKGROUND

Recent studies suggest an association between 6-thioguanine (6-TG) therapy and hepatic nodular regenerative hyperplasia (NRH) in patients with inflammatory bowel disease (IBD). An influence of 6-TG on portal pressure remains to be determined. The aim of the study was to examine the functional relevance of long-term 6-TG treatment on hepatic hemodynamics in IBD patients and its association with NRH.

METHODS

Patients treated with 6-TG for IBD underwent measurement of the hepatic venous pressure gradient (HVPG) and liver biopsy. 6-TG therapy was stopped when NRH was diagnosed. If elevated, HVPG measurement was repeated after 1 yr.

RESULTS

Twenty-six patients (15 women, 11 men; median age 41 yr, range 23-76) treated with 6-TG for 38 months (median; range 12-45) were included. Among 24 patients with sufficient liver biopsy, 6 patients (25%) were diagnosed with NRH. In these 6 patients, the HVPG was higher (median HVPG 7 mmHg, range 3-14) than in the 18 patients without NRH (median 3 mmHg, range 2-5; P < 0.001). In the patients with NRH, two had clinically significant portal hypertension (CSPH) (13 and 14 mmHg, respectively); in one patient the HVPG was slightly elevated (7 mmHg). No overt clinical signs of portal hypertension were observed. One year after stopping 6-TG therapy, HVPG decreased in all 3 patients with initially elevated HVPG levels.

CONCLUSIONS

We demonstrate that IBD patients under long-term 6-TG therapy are at a substantial risk for developing NRH. NRH results in elevation of HVPG and may cause CSPH. Discontinuation of 6-TG therapy extenuates portal hypertension and may thus reduce the risk of complications.

Thiopurine-induced liver injury in patients with inflammatory bowel disease: a systematic review

The mean prevalence of azathioprine (AZA) or 6-mercaptopurine (MP)-induced liver injury in patients with inflammatory bowel disease was approximately 3%, and the mean annual drug-induced liver disorder rate was only 1.4%. However, this low figure calculated from retrospective studies contrasts with a much higher incidence (>10%) reported by a prospective study. Thiopurine-induced hepatotoxicity can be grouped into three syndromes: hypersensitivity, idiosyncratic cholestatic reaction, and endothelial cell injury (with resultant raised portal pressures, veno-occlusive disease, or peliosis hepatis). A small percentage of patients present with a slight elevation of liver tests (LTs) that do not have clinical implications and LTs return to normal values during the follow-up, indicating that it is not always necessary to adjust the dose of the immunomodulator. However, when abnormalities in LTs are more marked, the dose of AZA/MP may be reduced 50%, with posterior clinical and analytical controls. With this strategy, LTs frequently normalize spontaneously, and the initial AZA/MP dose may be cautiously prescribed again. Thiopurines may induce an unusual severe cholestatic jaundice that may not regress but even progress despite thiopurine withdrawal. Therefore, these drugs should be completely withdrawn, and not only tapered, in those patients presenting clinically significant jaundice. Despite a lack of evidence that monitoring of LTs is necessary in patients receiving AZA/MP, routinely performed laboratory controls including LTs seem recommendable. However, the optimal monitoring schedule remains to be established. As long-term hepatotoxicity seems to be an unpredictable and potentially severe adverse drug reaction of 6-thioguanine, this drug should not be administered outside a clinical trial setting. (Am J Gastroenterol 2007;102:1518-527).

Thiopurine treatment in inflammatory bowel disease: clinical pharmacology and implication of pharmacogenetically guided dosing

This review summarises clinical pharmacological aspects of thiopurines in the treatment of chronic inflammatory bowel disease (IBD). Current knowledge of pharmacogenetically guided dosing is discussed for individualisation of thiopurine therapy, particularly to avoid severe adverse effects. Both azathioprine and mercaptopurine are pro-drugs that undergo extensive metabolism. The catabolic enzyme thiopurine S-methyltransferase (TPMT) is polymorphically expressed, and currently 23 genetic variants have been described. On the basis of an excellent phenotype-genotype correlation for TPMT, genotyping has become a safe and reliable tool for determination of a patient's individual phenotype. Thiopurine-related adverse drug reactions are frequent, ranging from 5% up to 40%, in both a dose-dependent and -independent manner. IBD patients with low TPMT activity are at high risk of developing severe haematotoxicity if pharmacogenetically guided dosing is not performed. Based on several cost-benefit analyses, assessment of TPMT activity is recommended prior to thiopurine therapy in patients with IBD. The underlying mechanisms of azathioprine/mercaptopurine-related hepatotoxicity, pancreatitis and azathioprine intolerance are still unknown. Although the therapeutic response appears to be related to 6-thioguanine nucleotide (6-TGN) concentrations above a threshold of 230-260 pmol per 8 x 10(8) red blood cells, at present therapeutic drug monitoring of 6-TGN can be recommended only to estimate patients' compliance.Drug-drug interactions between azathioprine/mercaptopurine and aminosalicylates, diuretics, NSAIDs, warfarin and infliximab are discussed. The concomitant use of allopurinol without dosage adjustment of azathioprine/mercaptopurine leads to clinically relevant severe haematotoxicity due to elevated thiopurine levels. Several studies indicate that thiopurine therapy in IBD during pregnancy is safe. Thus, azathioprine/mercaptopurine should not be withdrawn in strictly indicated cases of pregnant IBD patients. However, breastfeeding is contraindicated during azathioprine/mercaptopurine therapy. Use of azathioprine/mercaptopurine for induction and maintenance of remission in corticosteroid-dependent or corticosteroid-refractory IBD, particularly Crohn's disease, is evidence based. To improve response rates in thiopurine therapy of IBD, comprehensive analyses including metabolic patterns and genome-wide profiling in patients with azathioprine/mercaptopurine treatment are required to identify novel candidate genes.

Toxicity of 6-thioguanine: no hepatotoxicity in a series of IBD patients treated with long-term, low dose 6-thioguanine. Some evidence for dose or metabolite level dependent effects?

BACKGROUND

6-Thioguanine is used in inflammatory bowel disease since 2001, with promising short-term results. In 2003, liver histology of some 6-thioguanine treated patients showed nodular regenerative hyperplasia. Recently, magnetic resonance imaging revealed nodular regenerative hyperplasia in patients with normal histology.

AIMS

Investigating the presence of nodular regenerative hyperplasia in long-term 6-thioguanine treated patients.

PATIENTS AND METHODS

Inflammatory bowel disease patients, using 6-thioguanine minimally 24 months, were asked to undergo liver biopsy and magnetic resonance imaging.

RESULTS

Fourteen patients used 6-thioguanine minimally 24 months, 13 participated. Mean 6-thioguanine therapy duration, daily dose and 6-thioguanine nucleotide levels were: 36 months, 18.8 mg (0.28 mg/kg) and 705 pmol/8x10(8) erythrocytes, respectively. Liver histology and magnetic resonance imaging showed no nodular regenerative hyperplasia.

DISCUSSION

Liver biopsy and magnetic resonance imaging showed no nodular regenerative hyperplasia in these long-term 6-thioguanine treated inflammatory bowel disease patients. 6-thioguanine dose and metabolite levels were lower compared with previous nodular regenerative hyperplasia reports, suggesting dose or metabolite level-dependent effects. Otherwise, nodular regenerative hyperplasia is related with inflammatory bowel disease itself and immunosuppressives, including azathioprine and 6-mercaptopurine.

CONCLUSION

6-Thioguanine is debated due to nodular regenerative hyperplasia. We found no nodular regenerative hyperplasia in inflammatory bowel disease patients with long-term, low dosed 6-thioguanine, suggesting metabolite level-dependent effects. Therefore, 6-thioguanine still seems useful, but in selected patients, intolerant for other immunosuppressives, low dosed and under close surveillance of metabolite levels and hepatotoxity.

A systematic survey evaluating 6-thioguanine-related hepatotoxicity in patients with inflammatory bowel disease

OBJECTIVE

Drug-induced liver injury was recently reported as a major complication leading to hepatic nodular regenerative hyperplasia (NRH) in patients with inflammatory bowel disease (IBD) and 6-thioguanine (6-TG) therapy. The aim of the study was to evaluate the prevalence of 6-TG-related hepatotoxicity in a large multi-centered IBD population by means of a systematic online survey.

METHODS

Clinical and laboratory data, imaging techniques (sonography, CT, MRI) and histology of liver biopsies were surveyed in IBD patients treated with 6-TG. The decision on whether liver imaging and/or liver biopsy were performed was exclusively at the discretion of the investigator.

RESULTS

6-TG use was fully documented in 296 patients (median treatment duration 56 weeks, range < 1-207). Laboratory signs of drug-induced liver injury were found in 43 patients (14.5%). Liver imaging revealed pathologic results in 68/176 patients (38.6%). Liver biopsy was performed in a subset of 60 patients; using silver-reticulin staining (n = 59), NRH was considered in 16 patients (27.1%). Age was the only independent, albeit weak, risk factor for development of NRH.

CONCLUSION

This large online survey confirms the strong association between 6-TG treatment and the significant risk of development of NRH in patients with IBD. The definitive diagnosis of NRH depends solely upon liver biopsy.

Severe liver disease associated with prolonged exposure to antiretroviral drugs

BACKGROUND

Liver damage is frequently seen in HIV-positive subjects, often resulting from coinfection with hepatitis B and/or C viruses (HCV), alcohol abuse, etc. However, the etiology of liver disease still remains unknown for a small subset of individuals.

METHODS

Cryptogenic liver disease (CLD) was defined as persistently elevated aminotransferases levels in the absence of hepatitis C and/or B viruses replication and of other common causes of liver disease (alcohol, medications, etc). We identified cases initially meeting this definition by examining all HIV-positive subjects attended during the year 2004 in 2 large HIV clinics in Spain. Their clinical charts were retrospectively reviewed, and their assessment completed when needed to rule out other less frequent causes of liver disease. The stage of liver fibrosis was assessed by liver biopsy and/or elastography. To assess which factors could be associated with CLD, HIV-positive controls were chosen and matched by age, gender, and CD4 status.

RESULTS

CLD was diagnosed in 17 (0.5%) out of 3200 HIV-positive patients. Their mean age was 43 years, 82.4% were male, and 76% had acquired HIV through homosexual relationships. The mean time from HIV diagnosis was >15 years, and all patients had been exposed to antiretroviral therapy. Nevirapine, stavudine, and didanosine were the drugs more frequently used by this subset of patients. None of them had liver function test abnormalities before initiating antiretroviral therapy. Advanced liver fibrosis (F3-F4 Metavir scores) was recognized in 10 (58.8%) individuals, and 9 (52.9%) had developed symptomatic liver complications, including ascites (8), portal thrombosis (6), variceal bleeding (5), and encephalopathy (2). In the case-control analysis, prolonged didanosine exposure was the only independent predictor of developing CLD in this population.

CONCLUSIONS

CLD is an uncommon condition in HIV-positive individuals and might be associated with prolonged didanosine exposure. It may evolve causing severe liver complications, with variceal bleeding and portal thrombosis being particularly frequent.

Nodular regenerative hyperplasia: a reversible entity associated with azathioprine therapy

Azathioprine represents an effective and widely used immunosuppressant; however, there are increasing concerns about the hepatotoxicity of thiopurines because of an entity called "nodular regenerative hyperplasia" (NRH) observed in patients treated with 6-thioguanine. In line with this hypothesis, we report and comment on a patient with inflammatory bowel disease (IBD) diagnosed with NRH as a reversible but potentially serious hepatotoxic side-effect of azathioprine. Our report strengthens the importance of further safety studies to evaluate the aetiology and prevalence of NRH in IBD patients before general conclusions on the use of thiopurines can be drawn. Physicians caring for IBD patients need to be alert to this rare but serious complication.