OBJECTIVE: Nodular regenerative hyperplasia (NRH) is a rare vascular disorder of the liver. Clinically, patients present with portal hypertension with or without a cholestatic pattern of injury. Histologically, the liver parenchyma is composed of small nodules of hypertrophic hepatocytes surrounded by atrophic hepatocytes without significant fibrosis. Nodular regenerative hyperplasia is a difficult diagnosis on biopsy specimens, but biopsy remains the gold standard for diagnosis. In this retrospective review, cytokeratin 7 (CK7) immunohistochemistry (IHC) was used to aid in the diagnosis and further characterization of NRH and NRH-like changes.
METHODS: The H&E-stained slides, reticulin, and CK IHC were reviewed for 22 cases. The percentage of hepatocytes staining for CK7 (0%-100%), the location of staining (centrilobular hepatic progenitor cells vs periportal/bile ductular reaction), and the pattern of staining distribution (patchy or diffuse) were recorded for comparison.
RESULTS: Of the 22 cases, 9 were CK7 positive. Cases of NRH, however, expressed various degrees of CK7 positivity in centrilobular hepatic progenitor cells, unlike NRH-like changes, which were either CK7 negative or CK7 positive in periportal hepatocytes or in areas of bile ductular reaction.
CONCLUSIONS: In cases with the appropriate clinical history and histology, CK7 immunohistochemistry can be performed to distinguish nodular regenerative hyperplasia (primary) and NRH-like changes (secondary). In difficult cases, CK7 positivity in centrilobular hepatic progenitor cells can help confirm the diagnosis of NRH. These data support NRH as a true entity with a distinct pathophysiology from NRH-like changes.

Aim: The differential diagnosis of intrinsic nonfibrotic conditions that may lead to portal hypertension include hepatoportal sclerosis (HPS), nodular regenerative hyperplasia (NRH), and sinusoidal obstruction syndrome (SOS). In this article, we characterize the clinical features and outcome of these lesions when they manifest as portal hypertension. Methods: Data was collected through retrospective patient medical records. Results: Patients (HPS: 28, NRH: 17, SOS: 11) were identified more frequently in recent years. All groups presented with signs and symptoms of portal hypertension. All patients had complex medical histories. An elevated serum alkaline phosphatase occurred in all groups and an elevated bilirubin with SOS. Imaging of the liver with HPS and NRH suggested cirrhosis, which was not seen with SOS. 11%, 12%, and 9% of patients in the HPS, NRH, and SOS respectively, underwent transjugular intrahepatic portosystemic shunt placement to manage the complications of portal hypertension, while 43%, 24%, and 36% of patients respectively, received a liver transplant. Conclusions: Patients with HPS, NRH, and SOS had complex medical histories, likely contributing to the development of these lesions. They are recognized more frequently now. In contrast to HPS and NRH, SOS occurred in liver transplant recipients, was associated with elevated serum bilirubin, and imaging did not suggest the presence of advanced fibrosis/cirrhosis. Liver transplantation appeared to be a viable treatment for complications related to HPS and NRH. Retransplantation for SOS yielded mixed results. HPS, SOS, and NRH should be considered when evaluating liver specimens from patients with unexplained nonfibrotic portal hypertension. Key message: Intrinsic nonfibrotic causes of portal hypertension appear to be increasing in frequency. The differential diagnosis includes NRH, HPS, and SOS. These conditions are associated with complex diseases and possibly due to treatments. Pathologists need to be aware of this differential diagnosis when presented with liver biopsies performed to assess portal hypertension.

Nodular regenerative hyperplasia (NRH) is a primary disease of the liver that may cause noncirrhotic portal hypertension. Common causes include autoimmune, hematologic, immune deficiency, and myeloproliferative disorders. Given the limited data regarding the development of NRH in contemporary immunosuppressive protocols and the occurrence of NRH post-liver transplantation, we systematically reviewed NRH as it pertains to liver transplantation. We performed a comprehensive search for NRH and transplantation. Nineteen studies were identified with relevant data for NRH as an indication for a liver transplant. Thirteen studies were identified with relevant data pertaining to NRH development after liver transplant. Pooled analysis revealed 0.9% of liver transplant recipients had NRH. A total of 113 patients identified with NRH underwent liver transplantation. Most series report transplants done after the failure of endoscopic banding and TIPS management of portal hypertension. Reported 5-year graft and patient survival ranged from 73%-78% and 73%-90%. The pooled incidence of NRH after liver transplant for all indications was 2.9% and caused complications of portal hypertension. Complications related to portal hypertension secondary to NRH are a rare indication for a liver transplant. NRH can develop at any time after liver transplantation often without an identifiable cause, which may lead to portal hypertension requiring treatment or even re-transplantation.

Porto-sinusoidal vascular disease (PSVD) is the medical diagnosis for a patient who has portal hypertension in the absence of cirrhosis on liver biopsy. There are several specific histologic findings for PSVD, including obliterative portal venopathy, nodular regenerative hyperplasia, and incomplete septal fibrosis. Epidemiologic reports vary widely among regions; PSVD comprises less than 10% of causes of portal hypertension in Western countries but incidence has been found to be as high as 48% in India. There is an expansive list of etiologies that have been reported to cause PSVD.

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Porto-sinusoidal vascular disorder (PSVD) encompasses a group of vascular disorders characterized by lesions of the portal venules and sinusoids with clinical manifestations ranging from non-specific abnormalities in serum liver enzymes to clinically overt portal hypertension and related complications. Several reports have documented cases of PSVD in patients with systemic autoimmune conditions, such as systemic lupus erythematosus, systemic sclerosis, and rheumatoid arthritis. It is of note that these diseases share specific pathophysiological features with PSVD, including endothelial dysfunction, vascular inflammation, and molecular signatures. This narrative review aims to summarize the current knowledge on the association between PSVD and systemic autoimmune diseases, emphasizing the importance of promptly recognizing this condition in the rheumatological practice, and highlighting the key aspects where further research is necessary from both pathogenic and clinical perspectives.

OBJECTIVE: Systemic mastocytosis (SM) is characterized by the accumulation of atypical mast cells (MCs) in organs. Liver histology of SM has been marginally described and accurate histological classification is critical, given the consequences of aggressive SM diagnosis. We aimed to describe the histological features associated with liver SM using updated tools.
METHODS: Using the database of the French Reference Centre for Mastocytosis, we retrospectively identified patients with a liver biopsy (LB) and a diagnosis of SM. All LB procedures were performed according to the local physician in charge and centrally reviewed by an expert pathologist.
RESULTS: A total of 28 patients were included: 6 had indolent SM, 9 had aggressive SM, and 13 had SM with an associated hematologic neoplasm. Twenty-five (89%) patients presented hepatomegaly, and 19 (68%) had portal hypertension. The LB frequently showed slight sinusoid dilatation (82%). Fibrosis was observed in 3/6 indolent SM and in almost all advanced SM cases (21/22), but none of them showed cirrhosis. A high MC burden (>50 MCs/high-power field) was correlated with elevated blood alkaline phosphatase levels (p = .030). The presence of portal hypertension was associated with a higher mean fibrosis grade (1.6 vs. 0.8 in its absence; p = .026). In advanced SM, the presence of nodular regenerative hyperplasia (NRH) was associated with decreased overall survival (9.5 vs. 46.3 months, p = .002).
CONCLUSIONS: MC infiltration induced polymorphic hepatic lesions and the degree of fibrosis is associated with portal hypertension. NRH identifies a poor prognosis subgroup of patients with advanced SM. Assessing liver histology can aid in SM prognostic evaluation.

Telomere biology disorders (TBD) encompass several illnesses caused by underlying mutations in telomere maintenance leading to premature telomere attrition and telomere dysfunction. These disorders have unique features but share common disease manifestations including pulmonary fibrosis, cirrhosis, and bone marrow failure. The goals of this article are to provide an overview of the gastrointestinal and hepatic manifestations of TBD, focusing on their pathophysiology, clinical disease states, and current management strategies.
Telomere shortening has been observed in patients with chronic liver disease and is associated with a higher risk of progression to cirrhosis and portal hypertension. While the directionality of the association between telomere dysfunction and senescence on liver disease is not fully understood, research in TBD may provide clarity and could lead to future therapies for this increasingly prevalent disease. While treatment options remain limited in TBD-associated liver disease, recent studies point to the safety and efficacy of liver transplantation among patients with end-stage liver disease.

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.
METHODS: 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.

Inborn errors of immunity (IEIs) are a heterogeneous group of diverse clinical and genetic phenotypes that have an estimated combined prevalence as high as 1/1000. Increased risk of frequent, severe, or opportunistic infections is a common feature of IEIs, but there are also diverse immune-mediated, non-infective complications that are associated with significant morbidity and mortality. As patient survival increases, these are becoming more apparent within the liver. Hepatic involvement of IEIs may not only manifest as infections, but also nodular regenerative hyperplasia, granulomatous disease, autoimmune hepatitis and malignancy. As therapeutic options for patients are expanding, with both pharmaceutical treatments as well as haematopoietic stem cell transplant (HSCT), iatrogenic liver injury is increasingly common and important to identify. This review article summarises the spectrum of hepatic complications seen in IEIs, and highlights the challenges of management within this patient cohort, where immunosuppression is poorly tolerated. Early recognition and prompt diagnosis of potential hepatic complications is therefore crucial in ensuring potentially reversible causes are treated, but significant uncertainty remains regarding best practice for many features of immune dysregulation with limited high-quality evidence.