Chronic Viral Hepatitis

As in acute hepatitis, patients with chronic hepatitis have a wide spectrum of clinical manifestations that range from asymptomatic to symptomatic decompensated cirrhosis. Many patients are asymptomatic or have only mild, nonspecific complaints, such as fatigue. Findings on physical examination are typically few but include hepatomegaly and other stigmata of chronic liver disease, such as palmar erythema. Ascites and esophageal or cutaneous varices may also develop in patients with advanced cirrhosis. Serum aminotransferase levels fluctuate but are usually chronically elevated in the 2- to 10-fold range, although a substantial number of patients with mild chronic hepatitis C have persistently normal aminotransferase levels. Alkaline phosphatase and bilirubin levels are usually normal to mildly elevated unless hepatic decompensation has occurred, in which case high levels may be observed.

Hepatitis B

HBV contains a partially double-stranded, circular DNA genome and is a member of the hepadnavirus family of viruses. The complete viral particle, referred to as the Dane particle, consists of an outer envelope that surrounds a core of DNA, the hepatitis B core antigen (HBcAg), the hepatitis B e antigen (HBeAg), and DNA-dependent polymerase. The outer envelope contains the hepatitis B surface antigen (HBsAg). Both complete and incomplete viral particles circulate in the blood of infected patients. In fact, HBsAg can circulate in large quantities as incomplete tubular or spherical structures that lack DNA. Viral DNA may become incorporated into host DNA within infected hepatocytes, particularly in young patients, and these patients are at high risk for subsequent development of hepatocellular carcinoma. The viral antigen load and subsequent antibody response may be used as serologic markers to evaluate the time course of infection (Table 46.2).

HBV is transmitted through exposure to infected body fluids and by intravenous drug use, sexual contact, and occupational activity. Perinatal transmission is common (90%) if the mother is HBeAg positive, which is indicative of highly infectious disease and active viral replication, but less common (10%) if the mother is HBsAg positive. In high-prevalence areas, HBV infection is often acquired by maternal–neonatal transmission, which results in a high rate of chronic disease. In areas of low prevalence, hepatitis B is mainly a disease of young adults, who acquire the virus through parenteral or sexual exposure. Posttransfusion hepatitis B is virtually nonexistent in the United States because of routine screening of blood donors.

HBV is responsible for as many as 40% of cases of acute hepatitis in the United States. Clinical symptoms of acute hepatitis develop in approximately 30% of infected adults but in only 10% of children younger than 4 years of age; they typically appear 45 to 180 days after exposure.⁵ Fulminant hepatic failure occurs in approximately 1% of cases of acute hepatitis B. Acute liver failure may also occur in patients with chronic hepatitis B in which mutations are present in the precore, or core promoter, regions of the viral DNA.⁵ Chronic hepatitis develops in fewer than 10% of adult patients but in as many as 90% of infected infants. The rate of progression to cirrhosis depends on the presence or absence of active viral replication and the severity of liver damage (evident histologically). For instance, 50% of patients with chronic hepatitis B and marked activity progress to cirrhosis within 4 years. The annual probability that cirrhosis will develop is estimated to be 12% for patients with chronic hepatitis B. Hepatocellular carcinoma develops in 2.4% of patients with chronic hepatitis B annually, as well as in 0.5% of patients with chronic hepatitis without cirrhosis.⁵

Hepatitis C

HCV is a spherical, enveloped, single-stranded RNA virus that measures approximately 50 mm in diameter. It is classified as a separate genus within the Flaviviridae family. The genome for HCV is characterized by sequence heterogeneity, which is a result of pressure from the host immune system. This feature allows the virus to escape immune surveillance and establish chronic infection. Six major genotypes are recognized: the most common are 1a, 1b, 2a, and 2b.

HCV is transmitted primarily by parenteral exposure. Intravenous drug users and patients with hemophilia have a particularly high prevalence rate of infection. Intranasal cocaine use and sexual promiscuity are independent risk factors for acquisition of infection,⁶ although the risk associated with sexual transmission of HCV is low compared with the human immunodeficiency virus (HIV) or HBV.⁷ Although this virus was initially identified as the etiologic agent of transfusion-acquired “non-A, non-B” hepatitis, posttransfusion hepatitis C has decreased dramatically because of widespread implementation of donor screening. The risk of infection with HCV is now estimated to be 0.01% to 0.001% for each unit of blood transfused.⁷ Rates of perinatal transmission are estimated to be lower than 5%.

HCV accounts for approximately 15% of cases of acute hepatitis in the United States,² but acute infection is usually asymptomatic and only rarely recognized clinically. The incidence of acute HCV infection peaked in the late 1980s and early 1990s and has been steadily declining since, to less than 20 acute infections per 100,000 individuals per year .⁸ The incubation period of hepatitis C is 7 weeks, with a range of 2 to 30 weeks based on studies of transfusion-acquired cases.⁹ Fulminant hepatitis C is rare. Chronic infection is a far more common problem, occurring in at least 85% of infected patients. Most patients with chronic hepatitis C have few or no symptoms. Serum aminotransferase levels are often only mildly elevated, fluctuating from 1.5 to 10 times the upper limit of normal, and as many as 30% of patients have normal aminotransferase levels.¹⁰ Factors associated with progressive disease include patient age older than 40 years at the time of exposure, immunodeficiency, a high degree of viral heterogeneity, genotype 1, male gender, and long duration of infection.^8,10 Alcohol is known to potentiate viral replication and is associated with greater activity and fibrosis.¹¹ Although hepatic steatosis has been correlated with increased progression of fibrosis, it is unclear whether this result is confounded by associated metabolic abnormalities.⁸ Diagnostic tests currently in use include polymerase chain reaction (PCR) for detection of circulating viral RNA and a third-generation enzyme immunoassay for detection of anti-HCV antibodies.

The natural history of HCV infection has proved challenging to study, in part because of the difficulty in determining onset of infection. In most patients, the disease is believed to have an indolent course for as long as 2 decades; cirrhosis has developed in 20% to 40% of patients in studies with at least 10 to 20 years of follow-up.^8,12 Currently, chronic hepatitis C is the reason for 30% of liver transplantations performed in the United States. The risk of hepatocellular carcinoma in HCV-related cirrhosis is estimated to be approximately 1% to 4% per year.¹⁰

Occult HCV infection is a more recently recognized entity that has two distinct types of clinical presentation. The first type occurs in patients with persistently elevated liver function test results but negative serologic test results for HCV.^13,14 The second type is seen in patients with positive anti-HCV serology, absence of serum HCV-RNA, and normal liver function test results. In an initial study of 100 patients with elevated liver function test results and negative HCV serology, more than half were found to have HCV-RNA in their livers by reverse transcriptase (RT)-PCR and in situ hybridization.¹⁴ Preliminary studies have demonstrated that patients with occult HCV infection have higher triglyceride and cholesterol levels, decreased necroinflammatory scores and fibrosis, and fewer HCV-infected hepatocytes (by in situ hybridization).^13,15

Patients with hepatitis C may also be coinfected with HIV, especially high-risk individuals such as intravenous drug users. As many as 25% of HIV-infected individuals in North America are also infected with HCV.^16,17 Effective use of highly active antiretroviral therapy (HAART) has decreased the morbidity and mortality rates from HIV infection and increased the risk of death from other causes, such as hepatitis C liver disease.

HCV infection is associated with a variety of extrahepatic manifestations and is now thought to be responsible for most cases of essential mixed cryoglobulinemia.¹⁸ HCV is also strongly associated with porphyria cutanea tarda (PCT) in the United States, although there is marked geographic variation in the prevalence rate of HCV in patients with PCT.¹⁹ Homozygosity for the Cys282Tyr mutation in the hemochromatosis gene and HCV infection are significant risk factors for the expression of PCT, with heavy alcohol use often being a contributing factor.²⁰ The characteristic birefringent, yellow-brown, needle-shaped crystals described in PCT are rarely found in routinely processed liver biopsy specimens because they are highly soluble in water.

Hepatitis D

HDV, also known as the delta agent, is a small, defective RNA virus that requires HBsAg for packaging and transmission to cause infection and tissue injury. It is spread by mechanisms similar to those that transmit HBV, and it may manifest as a coinfection or superinfection with HBV. HDV infection can cause acute or chronic hepatitis. Coinfection or superinfection can cause fulminant hepatic failure. HDV infection should be suspected in all patients with hepatitis B in whom severe exacerbation of disease activity develops. The finding of anti-HDV antibody in a patient who is seropositive for HBsAg is diagnostic. Three genotypes are recognized.²¹ In general, the histologic features of HDV infection are not distinctive, but HDV is associated with more pronounced necroinflammatory activity and more rapid progression than is seen in patients with isolated HBV infection. Microvesicular fat may be present in severe cases.²² Delta antigen can be demonstrated by immunohistochemical means and is located primarily in hepatocyte nuclei.²²

Hepatitis E

HEV is a small, nonenveloped, single-stranded RNA virus that was originally classified in the family Caliciviridae but subsequently placed in the family Hepeviridae.²³ Hepatitis E is endemic in parts of Africa, India, southeast and central Asia, and Mexico. Fecal-oral transmission usually occurs through ingestion of contaminated water, although sporadic cases associated with animal contact or consumption have been documented.²³ HEV causes a mild form of acute hepatitis, which lasts 1 to 4 weeks in most patients but is particularly severe in pregnant women, in whom it is associated with an increased risk of acute liver failure and a mortality rate of as much as 25%. The incubation period is 4 to 5 weeks. Reports of histopathology indicate multiple patterns, ranging from a typical acute hepatitis morphologic picture, to a cholestatic form with canalicular bile plugs and cholestatic pseudorosettes, and, in a small series of patients with autochthonous infection, a severe form showing mixed portal and acinar inflammation with severe interface hepatitis and cholangiolitis.²⁵ Massive or submassive necrosis may occur in severe cases. Although HEV infection has been considered a self-limited disease, persistent infection has been documented in immunocompromised patients and in patients with HIV infection.²⁶ Serologic assays for anti-HEV IgG and IgM, and RT-PCR assay are used to confirm the clinical diagnosis.²⁴

Other Hepatitis Viruses

GB virus type C (GBV-C), also known as the hepatitis G virus, was discovered in 1995 and is a flavivirus in the same family as HCV. This virus has been detected in 1.7% of the population and can be transmitted parenterally and by vertical transmission.²⁷ Viral replication occurs predominantly in lymphocytes, although the virus is also detectable in hepatocytes.

The single-stranded, nonenveloped DNA virus known as TT virus was originally suspected to cause transfusion-associated hepatitis, but later it was found in more than 90% of Japanese blood donors, casting doubt on its role in causing disease.²⁸ Similarly, the related single-stranded circular DNA virus, the SEN virus, has also been found in patients with transfusion-associated hepatitis, although direct causality has not been established.²⁹

Massive and Submassive Necrosis

In severe cases of acute viral hepatitis, portions of the hepatocyte lobules (submassive necrosis) or entire contiguous lobules (massive necrosis) may undergo necrosis. Submassive necrosis usually involves zone 3 hepatocytes initially but may extend to zone 2 regions with progression. Extensive destruction of hepatic parenchyma results in the clinical syndrome of fulminant hepatic failure. On gross examination, livers with massive necrosis appear shrunken and flaccid, often showing wrinkling of the capsular surface and a mottled appearance of the liver parenchyma. Regenerating nodules of hepatocytes, which are often bile stained, may be irregularly distributed in the liver and may form nodular masses. The degree of necroinflammatory activity is variable, even among patients with a similar clinical course.³⁰ In fulminant cases, one often sees a prominent bile ductular reaction, with associated neutrophils (cholangiolitis), typically located in the peripheral region of the portal tracts (Fig. 46.5). However, the histologic features of submassive or massive hepatic necrosis are not specific for acute viral hepatitis. This pattern of injury can develop as a result of toxic injury, severe drug reaction, or Wilson disease, among other causes. A trichrome stain to highlight connective tissue is useful to distinguish massive hepatic necrosis from cirrhosis by demonstrating the lack of dense collagen deposition in the former. A reticulin stain is also helpful to demonstrate the presence of a collapsed reticulin framework.

Prognostic Factors

Pathologic features of acute viral hepatitis that are predictive of progression to chronicity are difficult to elucidate, in part because of the rarity of liver biopsies from patients with acute hepatitis. Furthermore, in patients with massive hepatic necrosis, an individual liver biopsy may not represent the overall status of the liver, because hepatocyte regeneration and necrosis can vary substantially from region to region.

Differential Diagnosis

Several major entities may be confused with acute viral hepatitis—in particular, chronic viral hepatitis, autoimmune hepatitis, and drug-induced hepatitis (Table 46.4). In cases in which the lobular inflammatory component is prominent, a markedly active chronic hepatitis may be confused with acute hepatitis. Some patients with autoimmune hepatitis exhibit an “acute” clinical picture and have a prominent lobular inflammatory infiltrate with extensive necrosis that may be difficult to distinguish from acute viral hepatitis. However, autoimmune hepatitis often reveals prominent plasma cell infiltrates (particularly in the portal tracts), marked periportal inflammation and necrosis, and mild bile duct injury. Also, in autoimmune hepatitis, fibrosis often exists at the time of presentation, even with an acute clinical picture. Serologic tests for autoimmune markers are usually helpful. Viral hepatitis also can be confirmed or excluded based on serologic or PCR-based testing, but some autoimmune markers, such as antinuclear antibody, are not always positive early in the course of autoimmune hepatitis.

Drug-induced hepatitis can be indistinguishable from acute viral hepatitis (see Chapter 48 for more detail). The presence of prominent eosinophils, granulomas, sinusoidal dilation, prominent bile ductular reaction, cholestasis, and fatty change may suggest a drug reaction, but these are not considered pathognomonic features. One helpful hint is that acute or chronic forms of hepatitis that do not seem to fit into a discrete morphologic category, or that show overlapping features such as cholestasis and lobular hepatitis, may represent a drug reaction. Obtaining a complete history of drug and toxin exposures is critical to disting repeated drug reactions from viral hepatitis. Furthermore, superimposed drug injury may develop in patients with acute viral hepatitis, so the two entities are not necessarily mutually exclusive. Kupffer cell aggregates are common in resolving acute viral hepatitis and should not be mistaken for non-necrotizing granulomas.

Portal Inflammation

Chronic hepatitis is characterized by the presence of inflammatory infiltrates that involve the portal tracts, which may range from mild and patchy to prominent and diffuse. The infiltrates consist primarily of lymphocytes, often with a variable number of plasma cells. Scattered macrophages, neutrophils, and eosinophils may be found in some cases but are typically a minor component of the infiltrate in chronic viral hepatitis. Lymphoid follicles may be present, particularly in hepatitis C, and germinal centers may also be seen (Fig. 46.6). A bile ductular reaction may be seen at the periphery of portal tracts, but this feature is not specific and usually is not very prominent in viral hepatitis. As with any type of bile ductular reaction, neutrophils are usually associated with the proliferating ductular epithelium as a result of cytokines released by biliary epithelium, and this should not be interpreted as evidence of biliary obstruction or acute cholangitis.

Interface hepatitis, also known as “interface activity” or “piecemeal necrosis,” is an important and common feature of chronic viral hepatitis, although it may be focal or even absent in cases with minimal or mild necroinflammatory activity. More commonly, the portal tracts appear equally involved by the inflammatory process; hence, variation within the liver may result in sampling error with regard to grading activity. Interface hepatitis has two main morphologic components: a mononuclear inflammatory infiltrate involving hepatocytes located at (and disrupting) the limiting plate, and injury or necrosis of periportal hepatocytes. Lymphocytes and plasma cells in the periportal infiltrate are closely associated with degenerating hepatocytes (Fig. 46.7), such that indentation of the cytoplasm of the hepatocytes occurs, and one might even see engulfment of inflammatory cells by hepatocytes. Hepatocytes in areas of interface hepatitis–associated necrosis often appear pale or swollen and show clumping of cytoplasm. Apoptotic bodies may be present as well.

Lobular Necroinflammatory Activity

In chronic viral hepatitis, hepatocyte necrosis is usually variable in severity and spotty in distribution. Lobular disarray, a feature characteristic of acute hepatitis, is not often prominent in chronic hepatitis unless there is marked activity. Apoptotic hepatocytes (acidophil bodies), which are usually more numerous in the periportal areas, may also be scattered in the hepatic lobules (Fig. 46.8). Mononuclear inflammatory cells tend to cluster around injured or dying hepatocytes (Fig. 46.9). Kupffer cells, in areas of spotty hepatocyte necrosis, may contain phagocytosed cellular debris. Hepatocyte swelling may be present in exacerbations of chronic viral hepatitis and may also be associated with zone 3 cholestasis. Regeneration of hepatocytes is recognized by the formation of liver cell plates that are two cells thick and by the formation of regenerating hepatocyte rosettes.

Fibrosis

Progressive fibrosis of the limiting plate, as a result of continued necroinflammatory activity, leads to enlargement of the portal tracts and stellate periportal fibrous extensions (Fig 46.10). Deposition of collagen and other extracellular matrix materials in the space of Disse at the leading edge of periportal fibrosis also results in capillarization of the sinusoids. Portal-portal fibrous septa represent the fibrous linkage of adjacent fibrotic portal tracts (Fig. 46.11). Portal-central fibrous bridges may also develop from superimposed episodes of severe lobular necroinflammatory activity involving zone 3 of the hepatic lobules. Central-central bridges form by the same mechanism but are far less common in chronic viral hepatitis. The end result of bridging fibrosis is cirrhosis, which is usually macronodular or of a mixed micronodular and macronodular type.

Nomenclature and Scoring

In the past, the term chronic active hepatitis was used to describe liver biopsies with interface hepatitis, and the term chronic persistent hepatitis was used for biopsies with portal inflammation but without significant periportal/piecemeal necrosis. This distinction was thought to be clinically important, because chronic persistent hepatitis was considered a relatively benign process without progression to significant liver disease. However, on identification of hepatitis C and on recognition of the waxing and waning nature of the disease and the prolonged time to progression to cirrhosis in many cases, this nomenclature has been abandoned. Currently, the recommended practice is to use the term “chronic hepatitis”³¹ and include a statement in the pathology report regarding severity of necroinflammatory activity (grade), extent of fibrosis (stage), and etiology.³² Prognostic factors should also be noted in the report (see later discussion).

Several different systems for scoring necroinflammatory activity and fibrosis have been developed. The original Knodell system, published in 1981, served as the prototype semiquantitative liver inflammation and fibrosis scoring system.³³ With modifications—such as the one proposed by Ishak and co-workers, which separates the grade of inflammation and necrosis from fibrosis—this system is still widely used, particularly in therapeutic trials in which the necroinflammatory activity in pretreatment and posttreatment liver biopsy specimens are compared.^34,35 In the original Knodell system, periportal necrosis (with or without bridging necrosis, intralobular necrosis, and inflammation), portal inflammation, and fibrosis are all assigned numeric values, which are then added to obtain a hepatitis activity index (HAI) that ranges from 0 to 22. One major criticism of this system is the inclusion of fibrosis (stage) as a determinant of activity (grade). In practice, the HAI is often modified so that bridging necrosis is dissociated from interface hepatitis, and only the elements that relate to grade are added together to produce the modified HAI (mHAI), with scores that range from 0 to 18; the stage, which indicates degree of fibrosis, is reported separately³⁶ (Table 46.6). An alternative grading system used by the French METAVIR Cooperative Study Group evaluates only two features (periportal necrosis and lobular necroinflammatory activity) instead of three; portal inflammation is excluded because it is considered a prerequisite for the diagnosis of chronic hepatitis, even in cases without parenchymal activity.³⁷

The various semiquantitative grading schemes, although useful for evaluating the effects of a particular treatment regimen in clinical trials, are typically not necessary or clinically relevant for routine pathology reporting of liver biopsies. For everyday diagnostic purposes, simpler schemes are sufficient. For instance, the Batts-Ludwig scoring system (Table 46.7) uses five categories (0 through 4) separately for both grade and stage³⁸ (Fig. 46.12; see also Fig. 46.13). In the Batts-Ludwig system, grade is determined by evaluation of the degree of interface activity (lymphocytic piecemeal necrosis), lobular inflammation, and necrosis. Stage is scored from 0 to 4. A zero score refers to normal connective tissue (no fibrosis). Stage 1 indicates fibrous of portal tracts with expansion; stage 2, periportal fibrosis; stage 3, portal-portal bridging fibrous septa; and stage 4, cirrhosis (Fig. 46.13). Pathologic stage is best evaluated with the use of a Masson trichrome stain, because delicate periportal or early bridging fibrous septa may not be easily apparent on hematoxylin and eosin (H&E) stain.

Prognostic Factors

Factors associated with progression of chronic viral hepatitis to cirrhosis may be divided into those related to specific viruses, host-related factors (see Treatment of Chronic Hepatitis C), and extraneous factors (e.g., alcohol use). For hepatitis C, development of chronic hepatitis is not related to the amount of virus at initial exposure. Viral genotype may be important in the progression of HCV infection. For instance, genotype 1 is associated with more severe disease than genotype 2.^10,55 However, other studies have not confirmed this association.⁵⁶ Host-related factors for disease severity are incompletely defined, but age at infection and gender appear to be relevant. Males and older individuals are more likely to show progression of fibrosis.^56,57 Alcohol consumption increases replication of hepatitis C and is associated with more severe disease.¹¹ In general, the grade of hepatic necroinflammatory activity in liver biopsy specimens correlates with the serum HCV RNA level,⁵⁸ and the rate of progression to cirrhosis correlates with high-grade activity and advanced stage in initial liver biopsies.⁵⁹ Hepatic steatosis is also associated with increased disease severity and is more commonly seen in infections with genotype 3b, as previously discussed.^57,60 Accumulation of iron in hepatocytes and Kupffer cells in hepatitis C may influence the disease course and response to therapy adversely.^57,61 However, many patients with chronic viral hepatitis, including hepatitis C, have abnormal results on serum iron studies but normal or only scant iron accumulation within the liver tissue.

Differential Diagnosis

The morphologic patterns of chronic viral hepatitis may resemble a variety of hepatitides and therefore are not specific (see Table 46.5). The initial distinction should include separation of acute from chronic hepatitis and then chronic viral hepatitis from other forms of chronic hepatitis, such as autoimmune hepatitis, primary sclerosing cholangitis (PSC), primary biliary cirrhosis (PBC), metabolic disorders, and drug reactions. Distinction from acute hepatitis rests primarily on the pattern of lobular inflammation and necrosis, and the finding of a predominance of portal inflammatory changes in cases of chronic hepatitis; fibrosis, in particular, is a cardinal sign of disease chronicity. However, in some cases, identification of acute versus chronic hepatitis may not be possible on morphologic grounds alone; clinical evidence of chronic disease can be helpful.

Early in the course of disease, portal lymphocytic infiltrates in patients with PBC may resemble chronic viral hepatitis, particularly hepatitis C. Florid-duct lesions and loss of interlobular bile ducts are helpful distinguishing features, because these lesions occur in PBC but not in chronic viral hepatitis. Bile ducts may be infiltrated mildly by lymphocytes in chronic hepatitis C, but the degree of inflammation and duct destruction is not nearly as severe as in PBC. Furthermore, portal granulomas, especially those associated with injured bile ducts, are not a feature of viral hepatitis. Chronic cholestasis is not a feature of precirrhotic chronic viral hepatitis and, by definition, indicates a chronic cholestatic condition. Furthermore, demonstration of increased copper or copper-binding protein by copper stains is helpful to suggest the presence of a chronic biliary disorder. Of course, knowledge of the status of viral serologic studies and other titers, such as the antimitochondrial antibody level, are most helpful in this differential diagnosis.

The morphologic features of PSC, in its early stages, may also overlap with chronic viral hepatitis. Both may show a marked portal lymphocytic infiltrate with interface hepatitis; however, this distinction may be particularly difficult in cases of childhood PSC. Once again, bile duct loss suggests a chronic biliary process; alkaline phosphatase levels are typically higher in PSC, but cholangiography is usually necessary to establish a final diagnosis of PSC. The classic “onion-skinning” periductal concentric sclerosing lesions of PSC are not seen in viral hepatitis. In patients with ulcerative colitis and a liver biopsy that shows a pattern of inflammation suggestive of chronic hepatitis, the possibility of PSC should always be strongly considered.

Chronic viral hepatitis may be histologically indistinguishable from autoimmune hepatitis. The presence of numerous plasma cells in the portal inflammatory infiltrate and plasma cells in the lobules is suggestive of autoimmune hepatitis, but an autoimmune-like pattern of hepatitis C has also been described, and clinical correlation is often necessary to reliably distinguish these entities. Bile duct infiltration by lymphocytes is also seen in autoimmune hepatitis and therefore cannot be used to distinguish this condition from hepatitis C. Once again, serologic studies are usually helpful and often diagnostic.

Wilson disease may also reveal a chronic hepatitis pattern of injury on liver biopsy, and it should always be considered as a possibility in biopsies from young patients with negative viral serology results. Low serum ceruloplasmin is suggestive, but quantitative copper studies on liver tissue are ultimately necessary for definitive diagnosis. α₁-Antitrypsin deficiency may also reveal a pattern of injury resembling chronic hepatitis; accumulation of PAS-positive, diastase-resistant cytoplasmic globules in periportal hepatocytes helps identify this disorder, particularly in liver biopsies from adults.

The spectrum of drug-induced injury in the liver is wide (see Chapter 48). Many types of drugs cause a chronic hepatitis morphologic pattern of injury that can be difficult to distinguish from other causes, such as viral or autoimmune hepatitis. Drugs that commonly cause chronic hepatitis include methyldopa, isoniazid, nitrofurantoin, dantrolene, and sulfonamides. As mentioned earlier, patterns of liver injury that show mixed features, prominent eosinophils, and cholestasis, or simply do not seem to fit in any discrete etiologic category, should always be considered for a drug reaction.

Mild lobular hepatitis, with spotty hepatocyte necrosis and a scant mononuclear inflammatory infiltrate, may be seen as a nonspecific finding in a variety of systemic and immune-mediated disorders and in patients with an intraabdominal inflammatory process. These changes may mimic mild acute or chronic hepatitis but are considered reactive in nature. In some cases, morphologic changes of chronic hepatitis in a liver biopsy specimen are not associated with a specific etiology after extensive serologic and clinical testing, and these cases may be labeled “cryptogenic” or “idiopathic.” However, a drug reaction should always be considered in this setting.

See Chapters 47 and 48 for more details on the differential diagnosis of hepatitis.

Treatment of Chronic Hepatitis C

HCV is estimated to infect approximately 170 million people worldwide and is the most common bloodborne chronic infection in the United States.^8,62–63 Despite a recent decline in the incidence of acute HCV infection and increasing understanding of its pathogenesis, the treatment of chronic hepatitis C remains challenging. Chronic HCV infection is still the most common indication for liver transplantation in the United States and Europe.^62,64

The treatment of chronic HCV infection is complicated for several reasons. Patients may be asymptomatic after their initial acute infection. Furthermore, a protracted period of time between initial infection and treatment has been associated with a poor response to therapy. Patients who are symptomatic often reveal advanced liver disease and respond poorly to therapy. In addition, biochemical tests, such as serum aminotransferases, are poor predictors of the severity of liver disease. Despite these limitations, several patient and viral characteristics have been associated with a poor response to treatment, including patient age greater than 40 years, male gender, high body weight, high viral load (>1×10⁶ HCV RNA copies per mL), cirrhosis, renal insufficiency, and infection with HCV genotype 1a or 1b.^62,63 However, detection of a single-nucleotide polymorphism in the IL28B gene has been found to be a better predictor of spontaneous clearing of HCV infection and sustained viral response after therapy than pretreatment RNA level, fibrosis stage, age, or gender.^64,65

Detailed treatment guidelines have been put forth by European and American liver associations.^64,65 Until recently, standard therapy for chronic HCV infection included the use of pegylated interferon and ribavirin.^64,65 Interferon-α is a cytokine that increases the innate antiviral immune response and results in decreased replication of HCV. Pegylated interferon has an increased half-life and can be administered as a weekly dose. Ribavirin is an oral nucleoside analogue with poorly understood antiviral activity, as well as immune-modulating activity.^62,63 More recently, however, the availability of direct-acting antiviral agents and protease inhibitors has resulted in improved sustained viral response rates (defined as the absence of HCV RNA in serum by a sensitive test at the end of treatment and 6 months later).^64,65

Cirrhosis and Regression of Fibrosis

Despite continued investigation into new therapeutic options for HCV infection, some studies show that as many as 40% of patients with chronic HCV infection will progress to cirrhosis and become candidates for orthotopic liver transplantation. Unfortunately, recurrence of HCV in liver transplants is virtually universal (see Chapter 52 for details).

Evaluation of liver biopsy specimens remains the gold standard for determination of the degree of fibrosis, despite limitations such as inadequate sampling and interobserver and intraobserver variability. The potential for reversal of liver fibrosis has long been controversial (see Chapter 50). For many years it was believed that, once established, scar tissue in the liver cannot be resorbed or replaced by healthy liver tissue. In the 1970s, several investigators questioned this assumption and investigated the potential reversibility of liver cirrhosis and the role of proteins such as collagenases in hepatic remodeling.⁶⁶ Some 40 years later, the idea of “regression” of hepatic fibrosis is more widely accepted and has been demonstrated in several rodent models and in human patients with autoimmune hepatitis, biliary obstruction, fatty liver disease, or viral hepatitis.^66–70 Basic science studies have also led to a better understanding of the pathogenesis of liver fibrosis through animal models, cell culture, and biochemical assays.^67,68 For instance, although hepatic stellate cells play a key role in hepatic wound healing and in matrix deposition and degradation, neutrophils and macrophages have also been shown to play a role in the degradation of matrix. Matrix metalloproteinases, which cleave collagen and other matrix components, may also be important in hepatic remodeling. Levels of tissue inhibitors of matrix metalloproteinases have been shown to decrease with fibrosis regression and clearance of activated hepatic stellate cells. The nuclear factor-κ B (NF-κB) pathway, transforming growth factor-β, and nerve growth factor also play a role in the complicated orchestration of matrix generation and degradation.^66–71 (See Chapter 50.)

Cytomegalovirus Infection in Otherwise Healthy Patients

Primary CMV infection in otherwise healthy people is usually self-limited, although a mononucleosis-like syndrome may occur in some. CMV hepatitis in immunocompetent individuals is often part of a multiorgan infectious process.⁸⁰ Rare cases of fulminant liver failure have been described, but chronic liver disease does not develop in this patient population. Liver biopsy findings resemble those of EBV infection. However, neither viral inclusions nor immunohistochemically demonstrable CMV antigen is typically evident in infected patients.⁸¹

Cytomegalovirus Infection in Immunocompromised Patients

CMV infection of the liver is more common in immunocompromised persons, and CMV is the single most important pathogen in solid organ transplant recipients of all types.⁸⁰ CMV infection may be acquired by primary infection, reactivation, or superinfection by a new strain in a previously seropositive patient.⁸² Infection occurs approximately 2 to 16 weeks after solid organ transplantation, and symptoms range from mild to life-threatening. Although any organ may be involved, hepatic involvement often predominates. In liver transplant recipients, the allograft is the most common site of involvement^82,83 (see Chapter 52). In immunocompromised patients, CMV hepatitis is caused primarily by the cytopathic effects of the virus.^84,85

Infected cells show both nuclear and cytoplasmic enlargement (hence the name, “cytomegalovirus”). Characteristic “owl’s eye” intranuclear viral inclusions (Fig. 46.20) and basophilic granular intracytoplasmic inclusions (Fig. 46.21) may be seen on routine H&E preparations. Inclusions may be present in the nucleus or cytoplasm of any liver cell type, Infected cells are often surrounded by a neutrophilic microabscess (Fig. 46.22), either with or without admixed mononuclear cells. The number of viral inclusions may be extremely variable, and the diagnosis is easily missed when few inclusions are present. In addition, some infected cells may have only a minimal amount of associated inflammation. However, the presence of typical neutrophilic microabscesses centered on injured and dying hepatocytes in a transplant patient should always trigger suspicion of CMV infection. Other associated features include hepatocyte apoptosis and focal necrosis, portal and lobular mononuclear inflammation, and rare granulomas, including those of the fibrin ring type.^86,87 Chronic liver disease does not occur in CMV-infected patients.

Cytomegalovirus Infection in Neonates

Liver involvement is a common feature of neonatal and perinatal CMV infection. Affected infants usually have hepatosplenomegaly and jaundice. Histologically, liver biopsy findings resemble opportunistic CMV infection, often with a variable number of typical viral inclusions. A wide range of other pathologic alterations also may be seen, such as portal inflammation, marked cholestasis, giant cell transformation, focal necrosis, and prominent extramedullary hematopoiesis.⁸⁸ Bile duct damage and obliteration are rarely present, although CMV (as well as several other viruses) has been associated with biliary atresia and paucity of intrahepatic bile ducts. In rare cases, portal or sinusoidal fibrosis may develop.

Useful diagnostic aids include viral culture, PCR assays, in situ hybridization, and CMV serologic studies and antigen tests.⁸² Isolation of CMV in culture does not imply active infection, because the virus may be excreted for months to years after the primary infection.⁸⁹

The differential diagnosis in otherwise healthy persons includes other viral infections (e.g., EBV). The differential diagnosis in immunocompromised patients includes herpesvirus and adenovirus infection. Other causes of microabscesses, such as ischemia, should also be considered, particularly in transplant recipients.⁹⁰ In neonates, the differential diagnosis includes other causes of neonatal hepatitis and congenital disorders of bile ducts, as discussed previously.

Tuberculosis

Liver involvement is present in almost all cases of miliary tuberculosis, and it is common both in localized extrapulmonary tuberculosis and in association with pulmonary tuberculosis. Signs and symptoms of liver disease may be the dominant or presenting features of tubercular infection. Although liver involvement is often asymptomatic, hepatomegaly, right upper quadrant pain, and fever may be present. Ascites and jaundice are less frequent. Patients may reveal elevated bilirubin and aminotransferase levels and a disproportionately high-alkaline phosphatase level.¹⁴¹ Confluent granulomas may lead to the formation of hepatic masses (tuberculomas) and periportal lymphadenopathy.^141,142

The histologic hallmark of hepatic tuberculosis is the formation of epithelioid granulomas, often accompanied by caseation and giant cells (Fig. 46.30, A). Similar changes can be seen within portal lymph nodes (see Fig. 46.30, B).The granulomas are usually small but may coalesce to form large nodules or masses with central liquefactive necrosis.¹⁴² Older lesions may show fibrosis, calcification, and occasionally amyloid.¹⁴³ Hepatic tuberculosis is often accompanied by reactive hepatitis. Because mycobacteria are usually difficult to detect on special stains (see Fig. 46.30, C), culture and PCR assays are of significant value.

Mycobacterium Avium-Intracellulare

Mycobacterium avium-intracellulare (MAI) infection is most commonly associated with, but is not limited to, patients with AIDS. The liver is involved in more than 50% of disseminated cases. Histologically, most liver biopsy specimens in immunocompromised patients show aggregates of foamy histiocytes in both the liver parenchyma and portal tracts (Fig. 46.31). Some patients, particularly those who are immunocompetent, have discrete epithelioid granulomas with associated neutrophils and lymphocytes. Giant cells and necrosis are rare.^144,145 Organisms are usually abundant in immunocompromised patients, as revealed by acid-fast staining, but are rare in immunocompetent persons. Occasionally, and particularly in patients with AIDS, MAI forms pseudosarcomatous, spindle cell nodules that mimic a neoplastic process¹⁴⁶ (Fig. 46.32). Culture and PCR assays may be useful diagnostic adjuncts. The differential diagnosis includes other causes of foamy macrophage aggregates, such as Rhodococcus equi infection and Whipple disease. Other atypical mycobacteria occasionally cause liver disease, including Mycobacterium kansasii and bacille Calmette-Guérin.

Leprosy

More than 60% of patients with lepromatous leprosy and about 20% of those with tuberculoid leprosy (both caused by infection with Mycobacterium leprae) show hepatic involvement.^147,148 Liver disease is often subclinical.¹²⁹ Histologically, the findings depend on the type of leprosy. In lepromatous leprosy, aggregates of foamy histiocytes (lepra cells) in portal tracts and lobules, often containing numerous acid-fast bacilli, are characteristic. Giant cells and discrete granulomas are only rarely present, and the degree of inflammation is typically minimal. In tuberculoid leprosy, discrete, tuberculoid granulomas with associated giant cells are characteristic (Fig. 46.33). Bacilli are rare in this variant. Some patients manifest both lepromatous and tuberculoid granulomatous lesions.¹⁴⁹

Bartonella Species

Bartonella henselae is the most common cause of cat scratch disease (CSD).¹⁵⁰ Patients usually have isolated lymphadenopathy in an area that drains the anatomic site of cat scratch inoculation, but a small percentage (1% to 2%) develop disseminated infection. These patients usually lack characteristic skin papules and superficial adenopathy but have generalized symptoms such as weight loss, fever, and malaise. Liver lesions are usually multiple and are often associated with abdominal lymphadenopathy.¹⁵¹ Patients with hepatic CSD are often younger than 10 years and are usually not immunocompromised. Patients typically respond well to antibiotic therapy.

The characteristic histologic lesions of hepatic CSD consist of irregular, stellate microabscesses surrounded by an inner layer of palisading histiocytes, a rim of lymphocytes, and an outermost thick layer of fibrous tissue (Fig. 46.34). The outer fibrous zone is quite pronounced. The lesions often vary widely within the same specimen, ranging from early microabscesses to “old” lesions consisting of fibrosis and granulation tissue.¹⁵¹ The differential diagnosis includes primarily other types of infections. A detailed patient history with specific questions pertaining to cat exposure is essential in establishing a correct diagnosis. Silver stains (Warthin-Starry or Steiner), molecular assays, and enzyme-linked immunosorbent assays are helpful diagnostic aids.

Both Bartonella species (henselae and quintana) are associated with hepatic bacillary angiomatosis-peliosis.¹⁵² These lesions consist of multiple, slitlike or cystic vascular spaces in a fibromyxoid stroma, associated with a mixed inflammatory infiltrate and focal necrosis¹⁵³ (Fig. 46.35). Bacillary angiomatosis-peliosis is usually found in HIV-positive patients and may mimic Kaposi sarcoma or other vascular tumors. The presence of well-formed vessels, a neutrophilic infiltrate, and organisms on silver precipitation staining helps to diagnose bacillary angiomatosis correctly.

Brucellosis

Brucellosis occurs primarily in domestic and barnyard animals and is highly endemic in the Mediterranean basin, India, Mexico, and Central and South America.¹⁵⁴ Humans contract infection through occupational exposure or ingestion of contaminated food or dairy products.¹⁵⁴ At presentation, patients typically have fever, malaise, headache, and arthralgias. Lymphadenopathy and hepatosplenomegaly may also be present. Hepatic involvement is seen in approximately 50% of cases.¹⁵⁵ Liver biopsies often show noncaseating granulomatous inflammation, sometimes with giant cells.^155–157 Granulomas may be discrete and epithelioid or small and poorly formed (Fig. 46.36) (akritidies). Some patients manifest only a nonspecific reactive hepatitis pattern of injury.^156–158 Organisms are difficult to culture and are only rarely visible on special stains. Serologic studies and an appropriate exposure history are most helpful in establishing a correct diagnosis.

Rickettsia and Similar Species

Most rickettsial illnesses affect the liver,¹⁵⁹ although involvement may be subclinical. Coxiella burnetii (causative agent of Q fever) is perhaps the most noteworthy because of its association with characteristic fibrin ring granulomas (Fig. 46.37).¹⁶⁰ True fibrin ring granulomas consist of a central lipid vacuole surrounded by a fibrin ring. However, some cases of Q fever have features intermediate between epithelioid and fibrin ring granulomas.^161,162 Rickettsia conorii, the causative agent of boutonneuse fever and South African tick bite fever, may cause either type of granulomas or a nongranulomatous reactive hepatitis.¹⁶³ Rickettsia rickettsii (Rocky Mountain spotted fever) induces a mixed portal inflammatory infiltrate, endotheliitis, cholestasis, and erythrophagocytosis.¹⁶⁴ Rickettsia typhi (murine typhus) may also involve the liver with similar histologic changes.¹⁶⁵ Because organisms are difficult to detect in rickettsial illnesses, immunofluorescent stains and serologic studies are quite helpful.

Human monocytic ehrlichiosis, a disease caused by the bacterium Ehrlichia chaffeensis and transmitted by the Lone Star tick found commonly in the south-central and southeastern United States, may also involve the liver. Histologic findings include scattered lobular foci of lymphohistiocytic infiltrates and diffuse lymphohistiocytic infiltration of the sinusoids with increased phagocytosis. Cholestasis is often present as well. Immunohistochemistry and serologic studies may be helpful because the ehrlichial morulae can be difficult to detect on H&E stain.¹⁶⁶

Whipple Disease

The Whipple bacillus (Tropheryma whippelii) can rarely infect the liver, even in the absence of small bowel involvement.^181,182 Histologically, PAS-positive bacilli are present in Kupffer cells. Often there is no significant inflammatory response, but epithelioid granulomas in association with Whipple disease are well documented.¹⁸² Electron microscopy and PCR assays may be useful diagnostic aids. The differential diagnosis includes infection by MAI or other intracellular organisms such as Histoplasma capsulatum and R. equi.

Other organisms that may infect the liver include Chlamydia, which can cause both perihepatitis (Fitz-Hugh–Curtis syndrome) and hepatitis; R. equi, which causes a granulomatous inflammatory pattern that mimics MAI infection; Clostridium perfringens, which can cause fulminant liver failure; and Pseudomonas pseudomallei (melioidosis), which can cause either small neutrophilic microabscesses or granulomas.

Miscellaneous Flagellates

Granulomatous hepatitis and cholangitis associated with Giardia lamblia have rarely been reported.²⁰²

The roundworm, Ascaris lumbricoides, is the most common source of human helminth infection. Clinical findings are variable and include hepatomegaly, cholecystitis, cholangitis, and hepatic abscess. Cholangitic superinfection by enteric bacteria is common. These are large worms (as great as 20 cm in length) and may be identified in the biliary tract, with accompanying reactive epithelial changes. Abscesses may contain worm remnants or, rarely, eggs with associated inflammation (often prominent eosinophils) and necrosis (Fig. 46.45).^209,210

Strongyloides stercoralis

Many patients with S. stercoralis infection are asymptomatic, but the worm’s capability for autoinfection allows it to reside in the host and produce illness for 30 years or more. Hepatic involvement is typically part of disseminated disease (Fig. 46.46). Infected livers show larvae in portal vessels and sinusoids. Associated inflammation ranges from none to a nonspecific mixed inflammatory infiltrate. Granulomas are sometimes seen.²¹⁶

Schistosomiasis is the most common cause of portal hypertension in the world. Most hepatobiliary disease is caused by Schistosoma mansoni, Schistosoma japonicum, or Schistosoma mekongi, because the organisms prefer mesenteric and portal veins. Once settled in their vein of choice, adult worms copulate and produce thousands of eggs in their lifetime; approximately 50% of the eggs remain in the body.²¹⁷ Hypersensitivity to the eggs is the underlying cause of disease, and the resultant inflammation eventually leads to fibrosis and obstructive hepatobiliary disease.^217,218 Symptomatic patients have splenomegaly and signs of portal hypertension, particularly bleeding. Hepatic function is usually preserved.

Grossly, infected livers are enlarged and nodular. On a cut surface, the typical pattern of portal fibrosis, known as pipestem or Symmers fibrosis, may be observed. Portal tracts are enlarged and stellate, but liver acinar architecture is usually unremarkable. Histologic features vary with the duration of disease. Early schistosomiasis features portal inflammation with numerous eosinophils, Kupffer cell hyperplasia, and focal hepatocyte necrosis, but ova are rarely present. In chronic disease, there is typically a granulomatous reaction to the eggs, which are present in varying numbers in both granulomas and fibrotic areas (Fig. 46.47, A through C). One usually sees associated mixed portal inflammation and giant cells. Ultimately, portal tracts become enlarged and densely sclerotic, with the development of fibrous septa that link the portal tracts together. Sinusoidal fibrosis may also develop. With progression of fibrosis, eggs may be difficult to detect. Schistosomal pigment, similar to malarial pigment, is often present in Kupffer cells and macrophages (see Fig. 46.46, D).^143,217,218 Granulomas and fibrosis may also affect portal vein branches and lead to phlebitis, sclerosis, and thrombosis. Eventually, portal veins are obstructed and destroyed, with subsequent proliferation of hepatic arterial branches.¹⁴³

The eggs are large. S. mansoni has an acid-fast shell (see Fig. 46.46, E) and a prominent lateral spine, but exact speciation of schistosomes in the liver is difficult. The nematode Capillaria should always be considered in the differential diagnosis, because the eggs are similar in appearance.

Other trematodes that may infect the liver and biliary tract include flukes; Clonorchis sinensis and Opisthorchis species, which are associated with development of cholangiocarcinoma^219,220; and Fasciola hepatica, which can cause calculi, cholangitis, obstructive jaundice, and granulomatous hepatitis.²²¹

Hydatid disease is often subclinical, but some patients develop hepatomegaly, marked abdominal enlargement and distention, and ascites. Secondary infection of the cysts may also develop. Ultimately, some patients experience liver failure, portal hypertension, involvement of adjacent organs, and death.^222–224 Grossly, the cysts are large, unilocular, and round (Fig. 46.48, A). The cyst fluid is strikingly antigenic and may lead to anaphylaxis on spillage. The inner layer of the cyst consists of a thin lining of epithelial cells that gives rise to the “brood” capsules from which scolices, or immature heads of adult worms, develop (see Fig. 46.48, B). The outer cyst layers are composed of hyalinized, PAS-positive material surrounded by granulation tissue and fibrosis.²²⁵ Daughter cysts may develop in the main cyst. The differential diagnosis includes other types of cystic lesions. The scolex of the worm distinguishes hydatid disease from amebic abscess, pyogenic abscess, and noninfectious processes such as fibropolycystic liver disease.