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ABSTRACT Hepatic injuries in COVID-19 are not yet fully understood and indirect pathways (without viral replication in the liver) have been associated with the activation of vascular mechanisms of liver injury in humans infected with SARS-CoV-2. Golden Syrian hamsters are an effective model for experimental reproduction of moderate and self-limiting lung disease during SARS-CoV-2 infection. As observed in humans, this experimental model reproduces lesions of bronchointerstitial pneumonia and pulmonary vascular lesions, including endotheliitis (attachment of lymphoid cells to the luminal surface of endothelium). Extrapulmonary vascular lesions are well documented in COVID-19, but such extrapulmonary vascular lesions have not yet been described in the Golden Syrian hamster model of SARS-CoV-2 infection. The study aimed to evaluate microscopic liver lesions in Golden Syrian hamsters experimentally infected with SARS-CoV-2. In total, 38 conventional Golden Syrian hamsters, divided into infected group (n=24) and mock-infected group (n=14), were euthanized at 2-, 3-, 4-, 5-, 7-, 14-, and 15-days post infection with SARS-CoV-2. Liver fragments were evaluated by histopathology and immunohistochemical detection of SARS-CoV-2 Spike S2 antigens. The frequencies of portal vein endotheliitis, lobular activity, hepatocellular degeneration, and lobular vascular changes were higher among SARS-CoV-2-infected animals. Spike S2 antigen was not detected in liver. The main results indicate that SARS-CoV-2 infection exacerbated vascular and inflammatory lesions in the liver of hamsters with pre-existing hepatitis of unknown origin. A potential application of this animal model in studies of the pathogenesis and evolution of liver lesions associated with SARS-CoV-2 infection still needs further evaluation.
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Acute COVID-19 infection is followed by prolonged symptoms in approximately one in ten cases: known as Long COVID. The disease affects ~65 million individuals worldwide. Many pathophysiological processes appear to underlie Long COVID, including viral factors (persistence, reactivation, and bacteriophagic action of SARS CoV-2); host factors (chronic inflammation, metabolic and endocrine dysregulation, immune dysregulation, and autoimmunity); and downstream impacts (tissue damage from the initial infection, tissue hypoxia, host dysbiosis, and autonomic nervous system dysfunction). These mechanisms culminate in the long-term persistence of the disorder characterized by a thrombotic endothelialitis, endothelial inflammation, hyperactivated platelets, and fibrinaloid microclots. These abnormalities of blood vessels and coagulation affect every organ system and represent a unifying pathway for the various symptoms of Long COVID.
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COVID-19 , Trombosis , Humanos , Síndrome Post Agudo de COVID-19 , SARS-CoV-2 , InflamaciónRESUMEN
BACKGROUND: Mifepristone, also known as RU-486, is an anti-progestational steroid with similar chemical structure to anabolic steroids. Given as a single dose in conjunction with misoprostol, mifepristone is used to induce medical abortion. Mifepristone administered chronically at a higher dose is also approved for the management of hypercortisolism. There have been only 2 reported cases of mifepristone associated liver injury, in both cases, in the setting of Cushing syndrome. We report a third patient with Cushing syndrome with mifepristone induced liver injury with unique histological findings that provide insight to the pathophysiology of liver injury in mifepristone and anabolic steroids. CASE PRESENTATION: Patient is a 63-year-old Caucasian female Cushing disease with no prior history of liver disease. She was started on mifepristone and semaglutide. Ninety days after initiating mifepristone, she developed deep jaundice, severe pruritus, fatigue, and nausea. Liver tests revealed a mixed hepatocellular/cholestatic pattern. Viral and autoimmune serologies were negative and there was no biliary dilatation on imaging. Liver biopsy showed severe cholestasis but no bile duct injury. Focal endothelialitis was present within a central venule. Cholestatic symptoms persisted for one month after presentation before slowly subsiding. Four months after stopping mifepristone, the patient's symptoms completely resolved, and liver tests became normal. Compilation of Roussell Uclaf Causality Assessment Method score indicated probable causality. CONCLUSIONS: Mifepristone shares a similar chemical structure as synthetic anabolic/androgenic steroids and there are many similarities in the clinical presentation of liver injury. This case and the 2 other reported cases share similar clinical characteristics. The observation of endothelialitis in our patient may provide a mechanistic link between mifepristone, or anabolic steroids in general, and the development of vascular complications such as peliosis.
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Aborto Inducido , Enfermedad Hepática Crónica Inducida por Sustancias y Drogas , Enfermedad Hepática Inducida por Sustancias y Drogas , Colestasis , Síndrome de Cushing , Embarazo , Femenino , Humanos , Persona de Mediana Edad , Mifepristona/efectos adversos , Síndrome de Cushing/inducido químicamente , Aborto Inducido/métodos , Enfermedad Hepática Inducida por Sustancias y Drogas/etiologíaRESUMEN
Novel Coronavirus Disease 2019 (Covid-19) is associated with multi-systemic derangement, including circulatory dysfunction with features of endothelial dysfunction, microangiopathic thrombosis and angiocentric inflammation. Recently, intussusceptive angiogenesis has been implicated in the pathogenesis of the disease. Herein, we conducted a narrative review according to the SANRA guidelines to review and discuss data regarding splitting angiogenesis including mechanisms, drivers, regulators and putative roles. Relevant angiogenic features in Covid-19, including their potential role in inflammation, endothelial dysfunction and permeability, as well as their use as prognostic markers and therapeutic roles are reviewed. Splitting angiogenesis in Covid-19 involve hypoxia, hypoxia-inducible factors, classic angiogenic mediators, such as the Vascular Endothelial Growth Factor (VEGF), Angiopoietins, hyperinflammation and cytokine storm, and dysregulation of the Renin-Angiotensin-Aldosterone System, which combined, interact to promote intussusception. Data regarding the use of angiogenic mediators as prognostic tools is summarized and suggest that angiopoietins and VEGF are elevated in Covid-19 patients and predictors of adverse outcomes. Finally, we reviewed the scarce data regarding angiogenic mediators as therapeutic targets. These preliminary findings suggest a potential benefit of bevacizumab as an add-on therapy.
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COVID-19 , SARS-CoV-2 , Humanos , Factor A de Crecimiento Endotelial Vascular , Inflamación , Angiopoyetinas , HipoxiaRESUMEN
The fight against coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 infection is still raging. However, the pathophysiology of acute and post-acute manifestations of COVID-19 (long COVID-19) is understudied. Endothelial cells are sentinels lining the innermost layer of blood vessel that gatekeep micro- and macro-vascular health by sensing pathogen/danger signals and secreting vasoactive molecules. SARS-CoV-2 infection primarily affects the pulmonary system, but accumulating evidence suggests that it also affects the pan-vasculature in the extrapulmonary systems by directly (via virus infection) or indirectly (via cytokine storm), causing endothelial dysfunction (endotheliitis, endothelialitis and endotheliopathy) and multi-organ injury. Mounting evidence suggests that SARS-CoV-2 infection leads to multiple instances of endothelial dysfunction, including reduced nitric oxide (NO) bioavailability, oxidative stress, endothelial injury, glycocalyx/barrier disruption, hyperpermeability, inflammation/leukocyte adhesion, senescence, endothelial-to-mesenchymal transition (EndoMT), hypercoagulability, thrombosis and many others. Thus, COVID-19 is deemed as a (micro)vascular and endothelial disease. Of translational relevance, several candidate drugs which are endothelial protective have been shown to improve clinical manifestations of COVID-19 patients. The purpose of this review is to provide a latest summary of biomarkers associated with endothelial cell activation in COVID-19 and offer mechanistic insights into the molecular basis of endothelial activation/dysfunction in macro- and micro-vasculature of COVID-19 patients. We envisage further development of cellular models and suitable animal models mimicking endothelial dysfunction aspect of COVID-19 being able to accelerate the discovery of new drugs targeting endothelial dysfunction in pan-vasculature from COVID-19 patients.
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COVID-19 , Células Endoteliales , Animales , Humanos , Biomarcadores , COVID-19/patología , Células Endoteliales/patología , Síndrome Post Agudo de COVID-19 , SARS-CoV-2RESUMEN
Pre-existing Alzheimer's disease is a risk factor for severe/fatal COVID-19 and infection by SARS-CoV2 virus has been associated with an increased incidence of un-masked Alzheimer's disease. The molecular basis whereby SARS-CoV2 may amplify Alzheimer's disease is not well understood. This study analyzed the molecular changes in autopsy brain tissues from people with pre-existing dementia who died of COVID-19 (n = 5) which was compared to equivalent tissues of people who died of COVID-19 with no history of dementia (n = 8), Alzheimer's disease pre-COVID-19 (n = 10) and aged matched controls (n = 10) in a blinded fashion. Immunohistochemistry analyses for hyperphosphorylated tau protein, α-synuclein, and ß-amyloid-42 confirmed the diagnoses of Alzheimer's disease (n = 4), and Lewy body dementia (n = 1) in the COVID-19 group. The brain tissues from patients who died of COVID-19 with no history of dementia showed a diffuse microangiopathy marked by endocytosis of spike subunit S1 and S2 in primarily CD31+ endothelia with strong co-localization with ACE2, Caspase-3, IL6, TNFα, and Complement component 6 that was not associated with SARS-CoV2 RNA. Microglial activation marked by increased TMEM119 and MCP1 protein expression closely paralleled the endocytosed spike protein. The COVID-19 tissues from people with no pre-existing dementia showed, compared to controls, 5-10× fold increases in expression of neuronal NOS and NMDAR2 as well as a marked decrease in the expression of proteins whose loss is associated with worsening Alzheimer's disease: MFSD2a, SHIP1, BCL6, BCL10, and BACH1. In COVID-19 tissues from people with dementia the widespread spike-induced microencephalitis with the concomitant microglial activation co-existed in the same areas where neurons had hyperphosphorylated tau protein suggesting that the already dysfunctional neurons were additionally stressed by the SARS-CoV2 induced microangiopathy. ACE2+ human brain endothelial cells treated with high dose (but not vaccine equivalent low dose) spike S1 protein demonstrated each of the molecular changes noted in the in vivo COVID-19 and COVID-19/Alzheimer's disease brain tissues. It is concluded that fatal COVID-19 induces a diffuse microencephalitis and microglial activation in the brain due to endocytosis of circulating viral spike protein that amplifies pre-existing dementia in at least two ways: 1) modulates the expression of proteins that may worsen Alzheimer's disease and 2) stresses the already dysfunctional neurons by causing an acute proinflammatory/hypercoagulable/hypoxic microenvironment in areas with abundant hyperphosphorylated tau protein and/or ßA-42.
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Enfermedad de Alzheimer , COVID-19 , Anciano , Humanos , Enfermedad de Alzheimer/complicaciones , Enfermedad de Alzheimer/genética , Enzima Convertidora de Angiotensina 2 , COVID-19/complicaciones , Células Endoteliales/metabolismo , ARN Viral , SARS-CoV-2 , Glicoproteína de la Espiga del Coronavirus , Proteínas tau/metabolismo , Sistema Nervioso CentralRESUMEN
Pulmonary capillary microthrombosis has been proposed as a major pathogenetic factor driving severe COVID-19. Autopsy studies reported endothelialitis but it is under debate if it is caused by SARS-CoV-2 infection of endothelial cells. In this study, RNA in situ hybridization was used to detect viral RNA and to identify the infected cell types in lung tissue of 40 patients with fatal COVID-19. SARS-CoV-2 Spike protein-coding RNA showed a steadily decreasing signal abundance over a period of three weeks. Besides the original virus strain the variants of concern Alpha (B.1.1.7), Delta (B.1.617.2), and Omicron (B.1.1.529) could also be detected by the assay. Viral RNA was mainly detected in alveolar macrophages and pulmonary epithelial cells, while only single virus-positive endothelial cells were observed even in cases with high viral load suggesting that viral infection of endothelial cells is not a key factor for the development of pulmonary capillary microthrombosis.
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COVID-19 , Trombosis , Células Endoteliales/metabolismo , Humanos , Pulmón/patología , ARN Viral , SARS-CoV-2 , Glicoproteína de la Espiga del Coronavirus , Trombosis/patología , TropismoRESUMEN
In 2020, infection with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) rapidly spread across the world to become a global pandemic. Coronavirus disease-2019 (COVID-19) is associated with a high rate of coagulopathy and thrombotic complications. The underlying mechanisms involved in these processes are complex. In addition to the low physical activity, blood coagulation activation accompanied by excessive immune/inflammatory reactions and vascular endothelialitis associated with the presence of intracellular SARS-CoV-2 and disrupted cell membranes contribute substantially to the complexity of the mechanisms. The types of thrombosis that occur include arterial thrombosis and venous thromboembolism. Microthrombi in alveolar capillaries are observed in COVID-19 patients. Considering the possible involvement of thrombosis in the worsening of COVID-19, prophylactic anticoagulant therapy, such as low-molecular-weight heparin or unfractionated heparin, is essential for patients with moderate and severe infections. Even with prophylactic anticoagulant therapy, the incidence of thrombosis remains high. Consequently, control of the underlying inflammation and vascular endothelial protection may be required in combination with anticoagulant therapy.
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Trastornos de la Coagulación Sanguínea , COVID-19 , Anticoagulantes , Heparina , Humanos , Pandemias , SARS-CoV-2RESUMEN
A 54-year-old patient with a history of pulmonary tuberculosis and occupational exposure to dust in early adulthood presented with symptoms of coughing with sputum, weight loss, occasional night sweats, and thoracic pain. Non-necrotizing granulomatosis in lung and lymph-node biopsies indicated sarcoidosis. Combined immunosuppressive therapy did not lead to an improvement. An atypical lung resectate with fibroinflammatory changes and obliterative endothelialitis may finally lead to the diagnosis of IgG4-associated lung disease with a bronchovascular pattern of involvement. The question discussed here is whether this is a coexistence of IgG4-associated lung disease with sarcoidosis or the spectrum of one disease.
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Inmunoglobulina G , Enfermedades Pulmonares , Adulto , Diagnóstico Diferencial , Granuloma , Humanos , Pulmón , Persona de Mediana EdadRESUMEN
This is the first autopsy report of hepatotoxicity from nivolumab immunotherapy for malignant mesothelioma. The increase in levels of biliary enzymes and randomly distributed endothelial damage were steroid-refractory, but second-line option was abandoned because of cachexia. Further discussions are needed regarding the customized management of immune-related toxicities.
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This clinical review paper discusses the pathophysiology of the pulmonary and cardiovascular manifestations of a SARS-CoV-2 infection and the ensuing implications on acute cardiovascular care in patients presenting with a severe COVID-19 syndrome admitted to an intensive acute cardiac care unit. The high prevalence of old age, obesity, diabetes, hypertension, heart failure, and ischaemic heart disease in patients who develop a severe to critical COVID-19 syndrome suggests shared pathophysiological mechanisms. Pre-existing endothelial dysfunction and an impaired innate immune response promote the development by the viral infection of an acute endothelialitis in the pulmonary microcirculation complicated by abnormal vasoconstrictor responses, luminal plugging by inflammatory cells, and intravascular thrombosis. This endothelialitis extends into the systemic circulation what may lead to acute myocardial injury, myocarditis, and thromboembolic complications both in the arterial and venous circulation.
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COVID-19/complicaciones , Enfermedades Cardiovasculares/etiología , Endotelio Vascular/patología , Pandemias , SARS-CoV-2 , COVID-19/epidemiología , Enfermedades Cardiovasculares/epidemiología , Salud Global , Humanos , IncidenciaRESUMEN
The objective of this study was to elucidate the pathophysiology that underlies severe COVID-19 by assessing the histopathology and the in situ detection of infectious SARS-CoV-2 and viral capsid proteins along with the cellular target(s) and host response from twelve autopsies. There were three key findings: 1) high copy infectious virus was limited mostly to the alveolar macrophages and endothelial cells of the septal capillaries; 2) viral spike protein without viral RNA localized to ACE2+ endothelial cells in microvessels that were most abundant in the subcutaneous fat and brain; 3) although both infectious virus and docked viral spike protein was associated with complement activation, only the endocytosed pseudovirions induced a marked up-regulation of the key COVID-19 associated proteins IL6, TNF alpha, IL1 beta, p38, IL8, and caspase 3. Importantly, this microvasculitis was associated with characteristic findings on hematoxylin and eosin examination that included endothelial degeneration and resultant basement membrane zone disruption and reduplication. It is concluded that serious COVID-19 infection has two distinct mechanisms: 1) a microangiopathy of pulmonary capillaries associated with a high infectious viral load where endothelial cell death releases pseudovirions into the circulation, and 2) the pseudovirions dock on ACE2+ endothelial cells most prevalent in the skin/subcutaneous fat and brain that activates the complement pathway/coagulation cascade resulting in a systemic procoagulant state as well as the expression of cytokines that produce the cytokine storm. The data predicts a favorable response to therapies based on either removal of circulating viral proteins and/or blunting of the endothelial-induced response.
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COVID-19/fisiopatología , Proteínas de la Cápside/metabolismo , SARS-CoV-2/patogenicidad , Glicoproteína de la Espiga del Coronavirus/metabolismo , Microangiopatías Trombóticas/fisiopatología , Enfermedades Vasculares/fisiopatología , Adulto , Anciano , Anciano de 80 o más Años , Enzima Convertidora de Angiotensina 2/metabolismo , Autopsia , COVID-19/virología , Proteínas de la Cápside/genética , Células Endoteliales/enzimología , Células Endoteliales/virología , Femenino , Humanos , Pulmón/fisiopatología , Pulmón/virología , Masculino , Microvasos/fisiopatología , Microvasos/virología , Persona de Mediana Edad , ARN Viral/genética , SARS-CoV-2/genética , Glicoproteína de la Espiga del Coronavirus/genética , Microangiopatías Trombóticas/virología , Enfermedades Vasculares/virología , ViriónRESUMEN
BACKGROUND: Coronavirus induced disease 2019 (COVID-19) can be complicated by severe organ damage leading to dysfunction of the lungs and other organs. The processes that trigger organ damage in COVID-19 are incompletely understood. METHODS: Samples were donated from hospitalized patients. Sera, plasma, and autopsy-derived tissue sections were examined employing flow cytometry, enzyme-linked immunosorbent assays, and immunohistochemistry. PATIENT FINDINGS: Here, we show that severe COVID-19 is characterized by a highly pronounced formation of neutrophil extracellular traps (NETs) inside the micro-vessels. Intravascular aggregation of NETs leads to rapid occlusion of the affected vessels, disturbed microcirculation, and organ damage. In severe COVID-19, neutrophil granulocytes are strongly activated and adopt a so-called low-density phenotype, prone to spontaneously form NETs. In accordance, markers indicating NET turnover are consistently increased in COVID-19 and linked to disease severity. Histopathology of the lungs and other organs from COVID-19 patients showed congestions of numerous micro-vessels by aggregated NETs associated with endothelial damage. INTERPRETATION: These data suggest that organ dysfunction in severe COVID-19 is associated with excessive NET formation and vascular damage. FUNDING: Deutsche Forschungsgemeinschaft (DFG), EU, Volkswagen-Stiftung.
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Infecciones por Coronavirus/patología , Trampas Extracelulares/metabolismo , Microvasos/patología , Neutrófilos/metabolismo , Neumonía Viral/patología , Trombosis/metabolismo , COVID-19 , Células Cultivadas , Infecciones por Coronavirus/complicaciones , Infecciones por Coronavirus/metabolismo , Endotelio Vascular/metabolismo , Endotelio Vascular/patología , Humanos , Microvasos/metabolismo , Neutrófilos/patología , Pandemias , Neumonía Viral/complicaciones , Neumonía Viral/metabolismo , Trombosis/etiología , Trombosis/patologíaRESUMEN
Severe acute respiratory syndrome corona virus 2 (SARS-CoV-2), the cause of COVID-19 disease, has the potential to elicit autoimmunity because mimicry of human molecular chaperones by viral proteins. We compared viral proteins with human molecular chaperones, many of which are heat shock proteins, to determine if they share amino acid-sequence segments with immunogenic-antigenic potential, which can elicit cross-reactive antibodies and effector immune cells with the capacity to damage-destroy human cells by a mechanism of autoimmunity. We identified the chaperones that can putatively participate in molecular mimicry phenomena after SARS-CoV-2 infection, focusing on those for which endothelial cell plasma-cell membrane localization has already been demonstrated. We also postulate that post-translational modifications, induced by physical (shear) and chemical (metabolic) stress caused respectively by the risk factors hypertension and diabetes, might have a role in determining plasma-cell membrane localization and, in turn, autoimmune-induced endothelial damage.
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Betacoronavirus/metabolismo , Infecciones por Coronavirus/virología , Proteínas de Choque Térmico , Neumonía Viral/virología , Proteínas Virales , Secuencia de Aminoácidos , Autoantígenos , Autoinmunidad , COVID-19 , Bases de Datos de Proteínas , Células Endoteliales/metabolismo , Proteínas de Choque Térmico/química , Proteínas de Choque Térmico/inmunología , Humanos , Epítopos Inmunodominantes , Imitación Molecular , Pandemias , SARS-CoV-2 , Proteínas Virales/química , Proteínas Virales/inmunologíaRESUMEN
Human parvovirus B19 (B19V) causes myriads of clinical diseases; however, owing to lack of awareness and undetermined clinical impact, it has failed to become a virus pathogen of global concern. Cryptically, B19V causes significant morbidity and mortality. Half of the world population and 60 per cent of Indians are known to be serologically naive and are at risk of acquiring B19V infections. Cumulatively, our data showed 21.3 per cent B19V-infected patients with juvenile chronic arthropathy, recurrent abortions, multi-transfused thalassaemia and leukaemia. In addition, B19V-infected cases that ended fatally included patients with pure red cell aplasia, fulminant hepatitis and haemophagocytic syndrome. Novel clinical associations of B19V observed were amegakaryocytic thrombocytopaenia, myositis and non-occlusive ischaemic gangrene of bowel. B19V possesses multiple receptors which are distributed widely in human tissues. Vascular endothelial cell infection by B19V causes endothelialitis and vasculitic injuries besides antibody-dependent enhancement which empowered B19V to cause multiorgan diseases. Owing to lack of suitable animal model for B19V, true causal role remains to be determined, but numerous reports on B19V infections substantiate a causal role in multiorgan diseases. Hence, B19V infections need to be recognized, investigated and treated besides making efforts on vaccine developments.
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Infecciones por Parvoviridae/complicaciones , Infecciones por Parvoviridae/epidemiología , Parvovirus B19 Humano/patogenicidad , Enfermedades Cardiovasculares/epidemiología , Enfermedades Cardiovasculares/virología , Femenino , Enfermedades Hematológicas/epidemiología , Enfermedades Hematológicas/virología , Humanos , India/epidemiología , Enfermedades Renales/epidemiología , Enfermedades Renales/virología , Hepatopatías/epidemiología , Hepatopatías/virología , Enfermedades del Sistema Nervioso/epidemiología , Enfermedades del Sistema Nervioso/virología , Infecciones por Parvoviridae/transmisión , Parvovirus B19 Humano/metabolismo , Embarazo , Complicaciones del Embarazo/epidemiología , Estudios SeroepidemiológicosRESUMEN
La biopsia hepática de los aloinjertos sigue siendo considerada el estándar de oro y juega un papel importante e integral en la interpretación y explicación de los cambios que puedan ocurrir en respuesta a alteraciones en las pruebas de la función o bioquímica hepática, anomalías funcionales o alteración en las imágenes diagnósticas, las cuales pueden, o no, ir acompañadas de síntomas. También es útil en el seguimiento o biopsias por protocolo (1-3). La evaluación de biopsias, después del trasplante, puede ser difícil debido a que es muy amplio el espectro de las complicaciones que pueden presentarse en el período postrasplante; más aún, cuando muchas de ellas necesitan un diagnóstico y tratamiento inmediato. La patología más frecuente es el rechazo agudo. Sin embargo, también pueden observarse cambios de perfusión/reperfusión, alteraciones funcionales, recidiva de enfermedad de base, lesión de la vía biliar, lesiones vasculares, infecciones oportunistas, patologías de novo, como la hepatitis autoinmune, hepatitis crónica idiopática postrasplante, toxicidad farmacológica o tumores, entre otras patologías (4). En este artículo relacionado con la patología del trasplante hepático se tratarán las patologías más frecuentes, no quirúrgicas, en el período postrasplante temprano, con un enfoque histopatológico dirigido a las dificultades y controversias para una adecuada correlación clínico-patológica.
Biopsies of liver allografts are still considered to be the gold standard. They play an important and integral role in the interpretation and explanation of changes that may occur in response to alterations in function tests, in the interpretation and explanation of liver biochemistry, in the interpretation and explanation of functional abnormalities, and in the interpretation and explanation of diagnostic images (whether or not accompanied by symptoms). Biopsies are also useful for monitoring and are often part of the protocol (1-3). The evaluation of biopsy samples after transplantation can be difficult especially because of the very broad spectrum of complications that may arise in the post-transplant period. Many of them require immediate diagnosis and treatment despite this difficulty. Although the most common condition is acute rejection, many other conditions and disorders can be observed. They include perfusion/reperfusion alterations, functional impairment, recurrence of underlying diseases, injury to the bile duct, vascular lesions, opportunistic infections, de novo pathologies such as autoimmune hepatitis, post-transplant idiopathic chronic hepatitis, drug toxicity, and tumors (4). This is the second article about the pathology of liver transplantation. It discusses the most common pathologies in the early post-transplant period and provides a histopathological approach towards difficulties and controversies for adequate clinicopathological correlation.