Liver histopathology of the hepatitis A virus infection: a comparison with hepatitis type B and non-a, non-b

Pediatric Acute Liver Failure: A Clinicopathological Perspective

Pediatric acute liver failure (PALF) is a life-threatening disorder characterized by acute hepatocellular injury occurring in children without recognized underlying liver disease. The clinicopathologic evaluation of PALF requires a different approach from that in adults. The diagnostic considerations differ depending on the age, personal and family history, geographical region, and clinical presentation. Distinct entities such as gestational alloimmune liver disease, herpes simplex virus infection, and metabolic disorders should be considered in neonates with acute liver failure, while acetaminophen toxicity and autoimmune hepatitis are more frequently seen in older children and adolescents. An identified cause for PALF despite a negative complete evaluation (indeterminate) is lacking in 30 to 50% of cases. Although not routinely performed in the setting of PALF, liver biopsy may be helpful in assessing the etiology, potential mechanisms of injury, determining the appropriateness of liver transplantation, and prognostication of the patients. In this article, we review the clinicopathologic characteristics of PALF with an emphasis on general approach of pathologic evaluation and histopathologic characteristic of selected entities.

Mechanisms of Hepatocellular Injury in Hepatitis A

Hepatitis A virus (HAV) infection is a common cause of acute viral hepatitis worldwide. Despite decades of research, the pathogenic mechanisms of hepatitis A remain incompletely understood. As the replication of HAV is noncytopathic in vitro, a widely accepted concept has been that virus-specific cytotoxic T cells are responsible for liver injury. However, accumulating evidence suggests that natural killer (NK) cells, NKT cells, and even non-HAV-specific CD8⁺ T cells contribute to liver damage during HAV infection. In addition, intrinsic death of virus-infected hepatocytes has been implicated as a cause of liver injury in a murine model of hepatitis A. Furthermore, genetic variations in host factors such as T cell immunoglobulin-1 (TIM1) and IL-18 binding protein (IL-18BP) have been linked to hepatitis A severity. This review summarizes the current knowledge of the mechanisms of hepatocellular injury in hepatitis A. Different mechanisms may be involved under different conditions and they are not necessarily mutually exclusive. A better understanding of these mechanisms would aid in diagnosis and treatment of diseases associated with HAV infection.

From hepatitis A to E: A critical review of viral hepatitis

Viral infections affecting the liver have had an important impact on humanity, as they have led to significant morbidity and mortality in patients with acute and chronic infections. Once an unknown etiology, the discovery of the viral agents triggered interest of the scientific community to establish the pathogenesis and diagnostic modalities to identify the affected population. With the rapid scientific and technological advances in the last centuries, controlling and even curing the infections became a possibility, with a large focus on preventive medicine through vaccination. Hence, a comprehensive understanding of hepatitis A, B, C, D and E is required by primary care physicians and gastroenterologists to provide care to these patients. The review article describes the epidemiology, pathogenesis, clinical presentation, diagnostic tools and current medication regimens, with a focus on upcoming treatment options and the role of liver transplantation.

Autoimmune liver disease following acute hepatitis A infection

A male patient in his late 30s presented to our outpatient clinic at Mortimer Market Centre with worsening liver transaminases tests 2 months after a resolved acute hepatitis A infection. A diagnosis of parainfectious autoimmune-like hepatitis phenomena was made based on the history, laboratory and histological features.

Comparative Pathology of Hepatitis A Virus and Hepatitis E Virus Infection

Hepatitis A virus (HAV) and hepatitis E virus (HEV) cause acute, self-limiting hepatic infections that are usually spread by the fecal-oral route in humans. Naturally occurring and experimental infections are possible in a variety of nonhuman primates and, in the case of HEV, a number of other species. Many advances in understanding the pathogenesis of these viruses have come from studies in experimental animals. In general, animals infected with these viruses recapitulate the histologic lesions seen in infected humans, but typically with less severe clinical and histopathological manifestations. This review describes the histopathologic changes associated with HAV and HEV infection in humans and experimental animals.

Acute and chronic hepatitis

Most liver biopsies performed today are for grading and staging of chronic viral hepatitis and steatohepatitis; there are uncommon indications for liver biopsy in the setting of acute hepatitis. Pathologists must have a broad knowledge of many forms of acute and chronic hepatitis, as well as their variations; these include viral hepatitis, autoimmune hepatitis, drug-induced hepatitis, metabolic diseases, and reactive hepatitis secondary to systemic disease processes. In this article, the authors review the pathological features of acute and chronic hepatitis.

[Hepatitis A]

Hepatitis A infection is known since the ancient Chinese, Greek and Roman civilizations but the first documented report was published in the eighteenth century. The hepatovirus belongs to the Picornaviridae family, and carries a single strand RNA. There are 7 genotypes. Antibodies of the IgM and IgA classes, during natural infections, appear early in the serum, together with the first clinical manifestations of the disease, but they may also appear at the end of the first week of infection. There is a spectrum of clinical presentation: asymptomatic infection, symptomatic without jaundice and symptomatic jaundiced. A rare fatal form of hepatitis has been described. Diagnosis of the hepatitis A infection is confirmed by the finding of IgM anti-HAV antibodies, routinely performed using an ELISA test. Treatment is supportive. Intramuscular anti-A gamma globulin is used for passive immune prophylaxis, and there is an efficient vaccine for active immune prophylaxis.

Hepatitis A: old and new

The hepatitis A virus (HAV), a picornavirus, is a common cause of hepatitis worldwide. Spread of infection is generally person to person or by oral intake after fecal contamination of skin or mucous membranes; less commonly, there is fecal contamination of food or water. Hepatitis A is endemic in developing countries, and most residents are exposed in childhood. In contrast, the adult population in developed countries demonstrates falling rates of exposure with improvements in hygiene and sanitation. The export of food that cannot be sterilized, from countries of high endemicity to areas with low rates of infection, is a potentially important source of infection. After ingestion and uptake from the gastrointestinal tract, the virus replicates in the liver and is excreted into the bile. Cellular immune responses to the virus lead to destruction of infected hepatocytes with consequent development of symptoms and signs of disease. Humoral immune responses are the basis for diagnostic serologic assays. Acute HAV infection is clinically indistinguishable from other causes of acute viral hepatitis. In young children the disease is often asymptomatic, whereas in older children and adults there may be a range of clinical manifestations from mild, anicteric infection to fulminant hepatic failure. Clinical variants include prolonged, relapsing, and cholestatic forms. Management of the acute illness is supportive, and complete recovery without sequelae is the usual outcome. Research efforts during World War II led to the development of passive immunoprophylaxis. Pooled immune serum globulin is efficacious in the prevention and attenuation of disease in exposed individuals. More recently, active immunoprophylaxis by vaccination has been accomplished. Future eradication of this disease can now be contemplated.

Liver biopsy in hepatitis C

The advent of more specific and sensitive assays for the diagnosis of hepatitis C has provided better definition of the histopathology of this disease and its differentiation from other forms of hepatitis. The following features have been found to be characteristic but not pathognomonic: lymphoid follicles in the portal tracts, bile duct lesions, fatty metamorphosis and Mallory body-like condensations in the cytoplasm of the hepatocytes. It has been suggested that the virus genotype may be correlated with different histopathologies. A better understanding of chronic hepatitis C has led to a more flexible and accurate terminology of chronic hepatitis, including the grade of necroinflammatory activity and the stage of fibrosis. Both seem to be of prognostic value in the course of chronic hepatitis C. Recurrence of hepatitis C in the graft after liver transplantation may have a different histopathologic pattern with progressive fibrosis, conspicuous cholestasis and pronounced hepatocellular necrosis. Histopathology grade and stage of liver damage in chronic hepatitis C is not reflected by serum aminotransaminase level or serological status.

Fibrosis and other histological features in chronic hepatitis C virus infection: a statistical model

AIMS

To study the inter-relation between hepatic fibrosis and other histological features of chronic hepatitis C virus (HCV) infection.

METHODS

Liver biopsy specimens from 200 consecutive patients with chronic HCV infection were graded and staged separately for necro-inflammatory activity and for fibrosis. The interaction between fibrosis and other histological features was evaluated by univariate and multivariate analysis, followed by hierarchical log linear modelling.

RESULTS

The most striking feature was the presence of portal tract inflammation in 177 (89%) of 200 samples. Lymphoid aggregates/follicles were observed either alone or as part of the general inflammatory infiltration of the portal tracts in 120 (60%) of 200 samples. Fatty change (macro- and microvesicular steatosis) was observed in 76 (38%) samples: mild to moderate in 60 (30%) and diffuse in 16 (8%). Bile duct damage was found in 30 (15%) of 200 specimens. Lobular activity was found in 154 (77%) of 200 samples and was significant in 44; piecemeal necrosis was present in 79 (40%). Thirty one (16%) patients had stage 0 liver fibrosis, 27 (14%) had stage 1, 69 (35%) had stage 2, 43 (22%) had stage 3, 16 (8%) had stage 4, and 12 (6%) had stage 5. On log linear analysis, piecemeal necrosis, lobular inflammation and steatosis were linked directly with fibrosis. Portal tract inflammation was linked directly and indirectly via piecemeal necrosis and lobular inflammation with fibrosis. The presence of lymphoid aggregates was associated with bile duct damage.

CONCLUSIONS

Portal tract inflammation with lymphoid aggregates or follicles, together with fatty change, bile duct damage and/or lobular activity, are characteristic of chronic HCV infection, confirming previous reports. Piecemeal necrosis, lobular inflammation, portal inflammation, and steatosis are linked directly with fibrosis in this statistical model, suggesting a close inter-relation in the development of fibrosis/cirrhosis.

Histologic activity of the liver in children with transfusion-associated chronic hepatitis C

Adults with chronic hepatitis C develop cirrhosis over a period of 6 to 20 years, but there are few reports of this disorder in children. To determine the histologic activity of chronic hepatitis C in children, we examined 31 biopsy specimens from 25 children (age range 3-16 years) with this disease. All patients were seropositive for antibody to hepatitis C virus by second-generation testing, and for HCV-RNA by the polymerase chain reaction. All cases were transfusion-associated. Patients were divided into two groups according to underlying disease: malignant disease or aplastic anemia (Group A, 17 cases) and non-malignant disease (Group B, eight cases). All patients in Group A, but only one in Group B, had received multiple transfusions. All patients in Group A had received intensive courses of cytotoxic and immunosuppressive agents. The histologic diagnosis was made using the standard criteria and Knodell's histology activity index. Chronic persistent hepatitis was more common in Group B (six patients) than in Group A (three patients). Chronic aggressive hepatitis 2B was found only in Group A (five patients). The mean histology activity index score was higher in Group A than in Group B (8.5 vs. 5.7). Six patients (four in Group A and two in group B) subsequently had a liver biopsy. The pathological diagnosis did not change after the second biopsy in any patient in Group B, while two patients in Group A showed a rapid progression of hepatitis. In each category of the histology activity index, periportal necrosis and intralobular necrosis were more severe in Group A than in Group B.(ABSTRACT TRUNCATED AT 250 WORDS)

Liver biopsy features of acute hepatitis C compared with hepatitis A, B, and non-A, non-B, non-C

The diagnosis of acute hepatitis C (AHC) often can only be suspected because current serologic tests remain negative for over 3 months. Because histologic features might provide useful clues, we reviewed 85 liver biopsy specimens from 85 patients with acute viral hepatitis, comparing 22 cases of AHC with 23 cases of acute hepatitis A (AHA), 30 cases of acute hepatitis B (AHB), and 10 cases of acute hepatitis non-A, non-B, non-C (AHNC). AHC was characterized by dense portal lymphoid aggregates (7 cases) and Poulsen-Christoffersen-type cholangitis (8 cases); these lesions were not found in any other type of acute viral hepatitis, and thus appeared to be diagnostic. Sinusoidal inflammatory infiltrates also were common in AHC, particularly in biopsy specimens obtained during the early phase of the disease. These inflammatory infiltrates did not appear to affect adjacent hepatocytes. Necrosis in AHC usually was spotty and accompanied by mixed inflammatory cells. In AHNC, necrosis was also spotty but, as an added feature, pigmented macrophages predominated in them. In AHA, necrosis was predominantly periportal, whereas in AHB, severe zone-3 necrosis predominated. Fatty changes were predominantly microvesicular; they were common in AHC but were also found in other groups. Collectively, the described histologic features allowed diagnosis of AHC in biopsy specimens with reasonable confidence. However, histologic findings failed to predict the prognosis in individual cases.

Histopathological and immunohistochemical studies of hepatitis A virus infection in marmoset Callithrix jacchus

Samples of serum, feces and liver tissue and organs of six cotton-eared marmosets Callithrix jacchus infected intravenously with two different strains of hepatitis A virus (HAV), were studied by conventional histologic techniques, by serological techniques and by immunocytochemical methods, such as immunofluorescence (IF) and peroxidase-antibody techniques. Hepatitis A antigen (HAAg) was detectable in daily collected stools, in liver biopsy obtained sequentially, and in organs collected at necropsy. Two marmosets also developed antibodies to HAV. By contrast, serum transaminases were not altered and there were histological hepatic lesions consistent with acute viral hepatitis in all inoculated animals. The data obtained, demonstrate that these primates are susceptible to human HAV and may be a useful animal model for the study of infection by this virus.

Histologic study of chronic active hepatitis C; comparison with chronic active hepatitis B

Reports on the histologic findings of chronic active hepatitis C (CAH-C) have been rare, and the characteristic histologic findings of CAH-C have been not yet determined. To compare the differences in the histologic findings between CAH-C and chronic active hepatitis B (CAH-B) group, we analyzed the histologic findings of 19 patients with CAH-C, who had positive tests for HCV-antibody by EIA, and 19 patients with CAH-B who had negative tests for HCV-antibody but positive tests for HBsAg by RIA. Histologic features were analyzed between the CAH-C and CAH-B groups using a scoring system which is modified from Knodell's histologic activity index-looking at portal inflammation, periportal necroinflammation, portal fibrosis, focal necrosis, regeneration, polyploid nuclear change, sinusoidal lymphocytic reaction and fatty change. Portal inflammatory cell infiltrations with prominent lymphocytes and follicular arrangement were more frequent in the CAH-C group (10 of 19 cases) than in the CAH-B group (5 of 19 cases). Severe sinusoidal lymphocytic reactions were also more prominent in the CAH-C group (11 of 19 cases) than in the CAH-B group (6 of 19 cases). However, periportal necroinflammation, portal fibrosis, focal hepatic necrosis, regeneration and polyploid nuclear changes were more prominent in the CAH-B group than in the CAH-C group. In conclusion, follicular portal inflammation and severe sinusoidal lymphocytic reactions were common histologic findings in serologically proven CAH-C when compared to CAH-B.

The pathology of hepatitis C

To determine the histologic pattern of hepatitis C, 54 liver biopsy specimens from 45 patients with a clinicopathological diagnosis of hepatitis C were studied. All patients were seropositive for antibody to hepatitis C virus by second-generation testing. Both transfusion-related and sporadic cases were included. More than half the samples showed chronic hepatitis without cirrhosis, whereas 44% showed developing or fully established cirrhosis. A histological pattern of mild chronic hepatitis with portal lymphoid follicles and varying degrees of lobular activity was found in many of the patients. Lymphoid aggregates or follicles were seen in 78% of biopsy specimens, but aggregates, less prominent than in hepatitis C, were also seen in 14 of 27 samples (52%) from patients with hepatitis B. We conclude that a characteristic histological pattern exists in chronic hepatitis C, that this pattern is not always found and that prominent lymphoid follicles, though not unique to hepatitis C, provide a useful diagnostic clue.

The significance of infections with two types of viral hepatitis demonstrated by histologic features in chimpanzees

In view of the recognized importance of necroinflammatory episodes in chronic hepatitis B virus (HBV) infection, chimpanzees, either HBV surface antigen (HBsAg) carriers or noninfected (naive), were infected with other primary hepatotropic viruses to evaluate histologic alterations and changes in virologic and biochemical markers of infection. The advantages of studies on chimpanzees are the availability of serial biopsy specimens and the viral type-specific histologic lesions, not as well recognized in humans. Infection with hepatitis A and non-A, non-B (NANB) agents produced more severe lesions in chronic HBsAg carrier chimpanzees than in naive animals. During this superinfection, the specific expression of the second agent was predominant, indicating that the exacerbation is caused by the second agent, but that carriers are prone to more severe disease than the naive chimpanzees. Hepatitis delta virus (HDV) infections were always coexistant with HBV and superinfection of carriers produced histologic changes more severe than those seen in any other type of viral hepatitis. Such HDV infections revealed less evidence of lymphocytotoxicity but rather of cytotoxicity, and sometimes resembled in appearance the histopathology of NANB. Coinfection of HDV and HBV and superinfection of HBV-carriers with NANB resulted in hepatitis that was far less severe than superinfection of HDV in HBV carriers, greatly in keeping with human experiences. HBV replication was suppressed transiently in both NANB and HDV superinfection. This implies that in exacerbations during chronic HBV infections of humans, suppression of HBV replication markers indicates superinfection, for instance, by NANB for which markers are so far not widely available; by contrast, elevated markers of HBV replication suggest reactivation of the original HBV infection.

Acute type A hepatitis presenting with hypotension, bradycardia, and sinus arrest

The cardiovascular complications of viral hepatitis are not widely recognized. Profound hypotension and a variety of dysrhythmias, including sinus arrest, have been reported in association with viral hepatitis, but most of these cases were described before the advent of specific viral serologic markers. Furthermore, previous instances of cardiovascular complications occurred during the course of an established viral syndrome. We report the cases of two previously healthy women who presented with unexplained hypotension and bradycardia as the initial manifestations of acute icteric hepatitis A. This phenomenon appears to represent a variant clinical presentation of a common viral entity.

Prolonged IgM antibodies and histopathological evidence of chronicity in hepatitis A

The case of a young man with hepatitis A and a chronic course is presented. The patient received a short course of steroid therapy for recurrence of symptoms following acute hepatitis A. Thereafter, liver enzymes have remained marginally elevated for 4 years and annual liver biopsies have shown evidence of chronicity. HAV IgM Ab persisted for 1034 days with subsequent development of HAV IgG Ab. The possibility of other viruses in the aetiology and the role of steroids in the development of chronicity are discussed.

Ultrastructural study of lymphocytic interaction with hepatocytes and endothelial cells in acute non-A, non-B hepatitis

In the liver biopsy specimens of all six patients with acute non-A, non-B hepatitis, the lymphocytic interaction with hepatocytes and sinusoidal endothelial cells was observed by electron microscopic study. Lymphocytes were in a close contact with damaged hepatocytes and interrupted endothelial cells, and the microvilli on the surface of these damaged hepatocytes were degenerated and lost. These findings pointed out the possibility that the lymphocyte may play one of the important roles in hepatocytic damage and endothelial cell damage in acute non-A, non-B hepatitis.

Viral hepatitis

Developments over the last four years in our understanding of viral hepatitis are analyzed. The molecular structure of hepatitis A has been established, and vaccines for prevention are under development. The recognition of the replicative and integrated stages of hepatitis B infection has allowed more rational approaches to therapy. Vaccines are of proven value. Delta virus infection has assumed an important role world wide as a cause of serious and fulminant liver disease in hepatitis B carriers. The agents for non-A, non-B virus hepatitis have eluded identification. These are important causes of chronic liver disease particularly in recipients of blood transfusion.

Cholestatic features in hepatitis A

The clinical, biochemical and histological characteristics of 13 cases of acute hepatitis A were evaluated. In 10 biopsies moderate to severe cholestasis was seen consisting of bile thrombi, cholestatic liver cell rosettes and ductular transformation of hepatocytes as shown on keratin- and S-100 immunostaining. The periportal spotty necrosis may play a role in the pathogenesis of cholestasis in hepatitis A by creating an interruption in continuity of bile flow. In 6 cases, abnormal ductular epithelium was seen resembling the ductular lesion in septicemia. Such ductular lesion may be related to the accumulation of leucotrienes as a result of cholestasis.

[Hepatitis non-A, non-B: epidemiologic, clinical, serologic and morphologic aspects]

Hepatitis non-A, non-B (HNANB) is due to one or more transmissible agents, probably viruses. Epidemiologically, HNANB is transmitted predominantly by transfusion of blood or plasma derivatives, and percutaneous inoculation, but a non-percutaneous transmission by the fecal-oral route is also established. However, despite 10 years of intense world-wide research, the transmissible agent, or agents, have not been identified and there are no serological assays for either an antigen or an antibody that can be used to detect this infection. The clinical diagnosis of HNANB remains, therefore, a diagnosis of exclusion mainly of hepatitis A and B, Epstein-Barr virus, cytomegalovirus and drug-induced liver disease. In contrast to hepatitis A and B, the clinical and biochemical course of HNANB tends to be less severe and the proportion of asymptomatic and anicteric cases is higher, but fulminant hepatitis and fatalities also occur. Typically, there is a fluctuating waxing and waning pattern of the serum aminotransferase activities in HNANB. HNANB has a relative high tendency to progress to a chronic stage. The exact frequency of HNANB-induced liver cirrhosis and convincing evidence for an association with hepatocellular carcinoma cannot be assessed, although the persistence of the infectious agent in chronic HNANB and the existence of a chronic asymptomatic carrier state have been proved. By light microscopy there is a broad morphologic spectrum of acute and chronic viral hepatitis, but no single pathognomonic lesion exists that allows a reliable distinction to be made of HNANB from hepatitis A and B. Electron microscopy of liver biopsy specimens of chimpanzees, experimentally infected with HNANB agents, permits the visualisation of cytoplasmic changes, which appear to be specific for infection with HNANB viruses. In human liver biopsy specimens from patients with HNANB, identical ultrastructural cytoplasmic changes could not consistently be demonstrated. In contrast, intranuclear aggregates of spherical and tubular particles measuring 20-29 nm, first described in experimental HNANB in chimpanzees, have been repeatedly demonstrated in acute and chronic HNANB in man. These nuclear particles have been considered as compelling evidence of human HNANB infection. The specificity has been challenged, however, by the demonstration of identical particles in other viral and non-viral hepatopathies and in liver biopsies of healthy volunteers. By immune electron microscopy, a multiplicity of virus-like particles are described in association with HNANB.(ABSTRACT TRUNCATED AT 400 WORDS)