Viral Hepatitis
Viral Hepatitis
Overview
5 hepatotropic viruses: HAV(faeco-oral,self-limit), HBV(parenteral,→chronic possible), HCV(was NANB, transfusion), HDV(delta,superinfects HBV), HEV(water-borne). Only HBV=DNA; rest RNA. (6th type=hep G exists etiologically.) Other viruses (EBV/arbovirus-yellow fever/CMV/HSV) cause nonspecific liver changes — NOT called “viral hepatitis.”
Hepatitis A
HAV: 27nm icosahedral non-enveloped ssRNA, 1 serotype. Inactivated: boil 1min/UV/formaldehyde/chlorine. 20-25% developing-world hepatitis. Benign self-limiting. Incubation 15-45d. FAECO-ORAL, overcrowding/poor sanitation. Age 5-14yrs commonest. NO carrier state.
Markers: IgM anti-HAV (symptom onset), IgG anti-HAV (post-illness, LIFELONG protection).
Hepatitis B
HBV DNA virus, incubation 30-180d, PARENTERAL+intimate contact (mother-child, sexual). Any age. Spectrum: acute, chronic, cirrhosis, fulminant, carrier. Role in HCC.
Particles: SMALL (22nm spheres+tubules, most numerous)=HBsAg excess. LARGE (42nm, DANE PARTICLES, double-shelled)=intact virion, 100-1000x fewer.
Genome (4 overlapping genes): S=HBsAg (major; pre-S1/S2→receptor+membrane proteins); P(largest)=DNA polymerase; C=HBeAg+HBcAg (nucleocapsid); X=HBxAg (transactivation: ↑HBV replication, ↑other virus replication incl HIV, ↑cytolytic-T susceptibility, pro-apoptotic) — linked to HCC via ↑HBV DNA replication.
Pathogenesis = IMMUNE-mediated not direct cytopathic (proof: carrier state exists without damage). ↓cellular immunity→persistent disease. CD8+ T cells attack HBcAg/HBeAg. Variable CD8+ cytokine response→determines outcome.
Markers (sequence): HBsAg(Australia antigen,Blumberg 1965,Nobel 1977)→6wk, active infection, >6mo persistence=CARRIER. Anti-HBs→3mo, LIFELONG protection. HBeAg→3-6wk transient, >10wk=chronic/carrier risk. Anti-HBe→seroconversion=GOOD prognostic sign. HBcAg→not in blood, only tissue (Orcein). Anti-HBc→IgM(4-6mo,RECENT) then IgG(REMOTE). HBV-DNA→most sensitive (Southern blot), earliest+persists.
Hepatitis D
HDV = DEFECTIVE virus, needs HBV helper. Nuclei of HBsAg+ patients. CO-INFECTION (simultaneous, healthy person) vs SUPERINFECTION (existing HBV carrier) — superinfection WORSE on every axis:
| Co-infection | Superinfection | |
|---|---|---|
| Fulminant risk | >HBV alone | >co-infection |
| Chronic risk | Rare | Much greater |
| Cirrhosis | Uncommon | More |
| Mortality | Rare | ~20% |
HCC LESS common in HBV+HDV vs HBV alone (paradox). HDV=36nm ssRNA double-shelled(outer=HBsAg,inner=delta Ag). DIRECTLY cytopathic (unlike HBV) — though not always. Endemic S.Europe/Middle East/S.India/Africa.
Hepatitis C
Was NANB (diagnosis of exclusion), now HCV. Blood/products/dialysis/IVDU/needle-pricks. 90% post-transfusion hepatitis = HCV. Incubation 20-90d(mean50). Acute MILDER than HBV but HIGHER chronicity progression — persistence = KEY feature. Cirrhosis 5-10yrs→HCC. NOW leading global chronic liver disease cause (surpassing HBV) — because milder acute+higher chronicity = the defining signature.
HCV=ssRNA enveloped, 30-60nm. Markers: anti-HCV IgG (3 generations, progressively earlier detection), HCV-RNA(PCR, confirms, earliest+persists).
Pathogenesis=cell-mediated: CD4+→cytokines→stimulate CD8+→antiviral cytokines. Stronger response=recovery, weaker=chronicity. HLA/innate immunity/NK cells modulate. Subset: anti-LKM crossreactivity → explains autoimmune hepatitis-HCV overlap.
Hepatitis E
Enteric, young/middle-age, India/Asia/Africa/C.America. Water contamination (post-monsoon). UNLIKE HAV: NO person-to-person spread. HIGH MORTALITY in PREGNANCY. Otherwise self-limited, NO chronic disease.
HEV=32-34nm ssRNA icosahedral non-enveloped. Markers: anti-HEV IgM/IgG (fall fast, no routine test), HEV-RNA.
Comparison table
| A | B | C | D | E | |
|---|---|---|---|---|---|
| Genome | RNA ss | DNA | RNA ss | RNA ss circular | RNA ss |
| Spread | Faeco-oral | Parenteral | Parenteral | Parenteral | Water |
| Incubation | 15-45d | 30-180d | 20-90d | 30-50d(super) | 15-60d |
| Chronicity | None | Occasional | COMMON | Common | None |
| Carrier | None | <1% | <1% | 1-10% | Unknown |
| HCC | No | + | + | ± | None |
Clinicopathologic spectrum
HAV/HEV: NO carrier, NO chronic hepatitis (both).
I. Carrier state: asymptomatic, transmits. 2 types: healthy carrier vs carrier-with-chronic-disease. HBV=most carriers worldwide (geographic: <0.5% US/W.Europe vs 5-20% Asia/tropics). HCV ~2-3% general population. Vulnerability: early age+impaired immunity — adults 10% become carriers vs NEONATES 90%. Dx: HBsAg >6mo. Morphology: healthy=none/ground-glass eosinophilic cytoplasm; chronic-disease carrier=chronic hepatitis/cirrhosis.
II. Asymptomatic infection: incidental ↑transaminases/antibody+.
III. Acute hepatitis — commonest outcome, A-E similar course. 4 phases:
- Incubation — asymptomatic but MOST infectious late incubation
- Pre-icteric — anorexia/nausea/vomiting/fatigue/malaise/arthralgia/headache, ±fever. Earliest lab=↑transaminases
- Icteric — jaundice, dark urine, clay stools, pruritus, tender hepatomegaly. Dx=LFTs+serology
- Post-icteric — recovery 2-12wk (longer for B/C). 1%→fulminant; 5-10%→chronic
Morphology: Gross=enlarged, soft, greenish. Micro:
- Hepatocellular injury (worst zone3/centrilobular): BALLOONING degeneration(mild)→ACIDOPHILIC degeneration/COUNCILMAN BODY(apoptosis)→dropout necrosis→BRIDGING necrosis(most severe, portal-central/central-central/portal-portal bands)
- Mononuclear infiltrate (portal→lobular)
- Kupffer cell hyperplasia
- Cholestasis (mild)
- Regeneration → fibrosis if reticulin collapses
Clues: HAV=panlobular heavy infiltrate. HCV=milder necrosis+fatty change+portal lymphoid aggregates+bile duct damage.
IV. Chronic hepatitis — >6mo continuing/relapsing. Mostly HBV/HCV/HBV+HDV; non-viral: Wilson’s, α1-AT deficiency, alcoholism, drugs, AUTOIMMUNE(lupoid — ANA/anti-smooth muscle/anti-mitochondrial+, LE cell+, viral markers NEGATIVE).
Old morphologic classification (persistent/active/lobular) SUPERSEDED — doesn’t predict prognosis. Real predictors: impaired immunity + extremes of age at infection. Now classified by ETIOLOGY + activity score.
Chronicity rates: HCV 40-60% adults (progressive→cirrhosis). HBV 90% infants, ~5% adults. HDV superinfection 10-40%. HAV/HEV none.
Morphology (HBV+HCV shared):
- PIECEMEAL necrosis — periportal at limiting plate, INTERFACE HEPATITIS (expanded portal tract lymphocyte/plasma/macrophage infiltrate) + ductule proliferation
- Portal tract lesions — “triaditis,” ductule proliferation; HCV: lymphoid follicles+germinal centres+bile duct damage
- Intralobular — usually architecture retained; focal necrosis, acidophilic bodies, Kupffer hyperplasia; severe=bridging necrosis; HCV=fatty change; HBV=GROUND-GLASS hepatocytes (HBsAg)
- BRIDGING FIBROSIS = irreversible damage marker — periportal→STELLATE portal tract→bridging (portal-portal/portal-central)→end-stage dense septa = POSTNECROTIC CIRRHOSIS
Grading (Knodell/Ishak HAI): necroinflammatory activity(0-4 periportal, 0-4/6 intralobular, 0-4 portal inflammation) + fibrosis stage(0-6, 6=cirrhosis).
Clinical: mild=transaminitis+fatigue; more=hepatomegaly/tenderness/splenomegaly; labs=↑PT/bilirubin/globulin/ALP. Immune complexes(HBV/HCV)→vasculitis/GN/cryoglobulinaemia. NO clinical-morphology correlation — course unpredictable. Long-standing HBV/HCV→HCC.
V. Fulminant hepatitis (submassive-massive necrosis) — MOST SEVERE acute form, rapid hepatocellular failure. SUBMASSIVE(<3mo, less rapid) vs MASSIVE(2-3wk, rapid).
Viral: ~half cases, mostly HBV/HCV, rare HAV; HEV serious in PREGNANCY; herpesvirus too. Non-viral: drugs(acetaminophen/NSAIDs/isoniazid/halothane/antidepressants), poisoning, hypoxic injury, malignant infiltration.
Presents: hepatic failure + encephalopathy. High mortality without transplant.
Morphology: Gross=SMALL SHRUNKEN (500-700g), loose wrinkled capsule, muddy-red/yellow necrosis (“acute yellow atrophy”), green bile staining. Micro: SUBMASSIVE=zones 3+2 wiped, collapsed reticulin, ORDERLY regeneration (may restore architecture). MASSIVE=entire lobules necrotic, only reticulin+portal tracts+bile-plugged ductules left, scanty inflammation, DISORDERLY regeneration, fibrosis usually ABSENT.
Vaccines
HAV: passive(Ig)+active(killed vaccine). HBV: active recombinant vaccine — pre-exposure(high-risk groups, 3 doses 0/1/6mo) + post-exposure(Ig+vaccine combo). HDV: prevented BY HBV vaccine. HCV: NO vaccine yet. HEV: uncertain Ig protection, no vaccine yet.
Clinical relevance
IgM/IgG anti-HBc split (recent vs remote) + HBeAg→anti-HBe seroconversion (resolution prognostic) = highest-yield serology facts. HBV/HDV pathogenesis being IMMUNE-mediated (not direct cytopathic) = explains carrier state existing at all — same fact explains immunosuppressed patients tolerating chronic HBV “quietly” but clearing it poorly. HDV co-vs-superinfection = remember as “superinfection worse on EVERY axis,” not 5 separate facts. HCV’s mild-acute+high-chronicity signature = explains why it surpassed HBV as leading chronic liver disease cause globally. Fulminant hepatitis submassive-vs-massive maps directly to regeneration quality (orderly/architecture-preserving vs disorderly) = the reasoning behind differing prognosis.
Viral Hepatitis
Overview
5 hepatotropic viruses: HAV(faeco-oral,self-limit), HBV(parenteral,→chronic possible), HCV(was NANB, transfusion), HDV(delta,superinfects HBV), HEV(water-borne). Only HBV=DNA; rest RNA. (6th type=hep G exists etiologically.) Other viruses (EBV/arbovirus-yellow fever/CMV/HSV) cause nonspecific liver changes — NOT called “viral hepatitis.”
Hepatitis A
HAV: 27nm icosahedral non-enveloped ssRNA, 1 serotype. Inactivated: boil 1min/UV/formaldehyde/chlorine. 20-25% developing-world hepatitis. Benign self-limiting. Incubation 15-45d. FAECO-ORAL, overcrowding/poor sanitation. Age 5-14yrs commonest. NO carrier state.
Markers: IgM anti-HAV (symptom onset), IgG anti-HAV (post-illness, LIFELONG protection).
Hepatitis B
HBV DNA virus, incubation 30-180d, PARENTERAL+intimate contact (mother-child, sexual). Any age. Spectrum: acute, chronic, cirrhosis, fulminant, carrier. Role in HCC.
Particles: SMALL (22nm spheres+tubules, most numerous)=HBsAg excess. LARGE (42nm, DANE PARTICLES, double-shelled)=intact virion, 100-1000x fewer.
Genome (4 overlapping genes): S=HBsAg (major; pre-S1/S2→receptor+membrane proteins); P(largest)=DNA polymerase; C=HBeAg+HBcAg (nucleocapsid); X=HBxAg (transactivation: ↑HBV replication, ↑other virus replication incl HIV, ↑cytolytic-T susceptibility, pro-apoptotic) — linked to HCC via ↑HBV DNA replication.
Pathogenesis = IMMUNE-mediated not direct cytopathic (proof: carrier state exists without damage). ↓cellular immunity→persistent disease. CD8+ T cells attack HBcAg/HBeAg. Variable CD8+ cytokine response→determines outcome.
Markers (sequence): HBsAg(Australia antigen,Blumberg 1965,Nobel 1977)→6wk, active infection, >6mo persistence=CARRIER. Anti-HBs→3mo, LIFELONG protection. HBeAg→3-6wk transient, >10wk=chronic/carrier risk. Anti-HBe→seroconversion=GOOD prognostic sign. HBcAg→not in blood, only tissue (Orcein). Anti-HBc→IgM(4-6mo,RECENT) then IgG(REMOTE). HBV-DNA→most sensitive (Southern blot), earliest+persists.
Hepatitis D
HDV = DEFECTIVE virus, needs HBV helper. Nuclei of HBsAg+ patients. CO-INFECTION (simultaneous, healthy person) vs SUPERINFECTION (existing HBV carrier) — superinfection WORSE on every axis:
| Co-infection | Superinfection | |
|---|---|---|
| Fulminant risk | >HBV alone | >co-infection |
| Chronic risk | Rare | Much greater |
| Cirrhosis | Uncommon | More |
| Mortality | Rare | ~20% |
HCC LESS common in HBV+HDV vs HBV alone (paradox). HDV=36nm ssRNA double-shelled(outer=HBsAg,inner=delta Ag). DIRECTLY cytopathic (unlike HBV) — though not always. Endemic S.Europe/Middle East/S.India/Africa.
Hepatitis C
Was NANB (diagnosis of exclusion), now HCV. Blood/products/dialysis/IVDU/needle-pricks. 90% post-transfusion hepatitis = HCV. Incubation 20-90d(mean50). Acute MILDER than HBV but HIGHER chronicity progression — persistence = KEY feature. Cirrhosis 5-10yrs→HCC. NOW leading global chronic liver disease cause (surpassing HBV) — because milder acute+higher chronicity = the defining signature.
HCV=ssRNA enveloped, 30-60nm. Markers: anti-HCV IgG (3 generations, progressively earlier detection), HCV-RNA(PCR, confirms, earliest+persists).
Pathogenesis=cell-mediated: CD4+→cytokines→stimulate CD8+→antiviral cytokines. Stronger response=recovery, weaker=chronicity. HLA/innate immunity/NK cells modulate. Subset: anti-LKM crossreactivity → explains autoimmune hepatitis-HCV overlap.
Hepatitis E
Enteric, young/middle-age, India/Asia/Africa/C.America. Water contamination (post-monsoon). UNLIKE HAV: NO person-to-person spread. HIGH MORTALITY in PREGNANCY. Otherwise self-limited, NO chronic disease.
HEV=32-34nm ssRNA icosahedral non-enveloped. Markers: anti-HEV IgM/IgG (fall fast, no routine test), HEV-RNA.
Comparison table
| A | B | C | D | E | |
|---|---|---|---|---|---|
| Genome | RNA ss | DNA | RNA ss | RNA ss circular | RNA ss |
| Spread | Faeco-oral | Parenteral | Parenteral | Parenteral | Water |
| Incubation | 15-45d | 30-180d | 20-90d | 30-50d(super) | 15-60d |
| Chronicity | None | Occasional | COMMON | Common | None |
| Carrier | None | <1% | <1% | 1-10% | Unknown |
| HCC | No | + | + | ± | None |
Clinicopathologic spectrum
HAV/HEV: NO carrier, NO chronic hepatitis (both).
I. Carrier state: asymptomatic, transmits. 2 types: healthy carrier vs carrier-with-chronic-disease. HBV=most carriers worldwide (geographic: <0.5% US/W.Europe vs 5-20% Asia/tropics). HCV ~2-3% general population. Vulnerability: early age+impaired immunity — adults 10% become carriers vs NEONATES 90%. Dx: HBsAg >6mo. Morphology: healthy=none/ground-glass eosinophilic cytoplasm; chronic-disease carrier=chronic hepatitis/cirrhosis.
II. Asymptomatic infection: incidental ↑transaminases/antibody+.
III. Acute hepatitis — commonest outcome, A-E similar course. 4 phases:
- Incubation — asymptomatic but MOST infectious late incubation
- Pre-icteric — anorexia/nausea/vomiting/fatigue/malaise/arthralgia/headache, ±fever. Earliest lab=↑transaminases
- Icteric — jaundice, dark urine, clay stools, pruritus, tender hepatomegaly. Dx=LFTs+serology
- Post-icteric — recovery 2-12wk (longer for B/C). 1%→fulminant; 5-10%→chronic
Morphology: Gross=enlarged, soft, greenish. Micro:
- Hepatocellular injury (worst zone3/centrilobular): BALLOONING degeneration(mild)→ACIDOPHILIC degeneration/COUNCILMAN BODY(apoptosis)→dropout necrosis→BRIDGING necrosis(most severe, portal-central/central-central/portal-portal bands)
- Mononuclear infiltrate (portal→lobular)
- Kupffer cell hyperplasia
- Cholestasis (mild)
- Regeneration → fibrosis if reticulin collapses
Clues: HAV=panlobular heavy infiltrate. HCV=milder necrosis+fatty change+portal lymphoid aggregates+bile duct damage.
IV. Chronic hepatitis — >6mo continuing/relapsing. Mostly HBV/HCV/HBV+HDV; non-viral: Wilson’s, α1-AT deficiency, alcoholism, drugs, AUTOIMMUNE(lupoid — ANA/anti-smooth muscle/anti-mitochondrial+, LE cell+, viral markers NEGATIVE).
Old morphologic classification (persistent/active/lobular) SUPERSEDED — doesn’t predict prognosis. Real predictors: impaired immunity + extremes of age at infection. Now classified by ETIOLOGY + activity score.
Chronicity rates: HCV 40-60% adults (progressive→cirrhosis). HBV 90% infants, ~5% adults. HDV superinfection 10-40%. HAV/HEV none.
Morphology (HBV+HCV shared):
- PIECEMEAL necrosis — periportal at limiting plate, INTERFACE HEPATITIS (expanded portal tract lymphocyte/plasma/macrophage infiltrate) + ductule proliferation
- Portal tract lesions — “triaditis,” ductule proliferation; HCV: lymphoid follicles+germinal centres+bile duct damage
- Intralobular — usually architecture retained; focal necrosis, acidophilic bodies, Kupffer hyperplasia; severe=bridging necrosis; HCV=fatty change; HBV=GROUND-GLASS hepatocytes (HBsAg)
- BRIDGING FIBROSIS = irreversible damage marker — periportal→STELLATE portal tract→bridging (portal-portal/portal-central)→end-stage dense septa = POSTNECROTIC CIRRHOSIS
Grading (Knodell/Ishak HAI): necroinflammatory activity(0-4 periportal, 0-4/6 intralobular, 0-4 portal inflammation) + fibrosis stage(0-6, 6=cirrhosis).
Clinical: mild=transaminitis+fatigue; more=hepatomegaly/tenderness/splenomegaly; labs=↑PT/bilirubin/globulin/ALP. Immune complexes(HBV/HCV)→vasculitis/GN/cryoglobulinaemia. NO clinical-morphology correlation — course unpredictable. Long-standing HBV/HCV→HCC.
V. Fulminant hepatitis (submassive-massive necrosis) — MOST SEVERE acute form, rapid hepatocellular failure. SUBMASSIVE(<3mo, less rapid) vs MASSIVE(2-3wk, rapid).
Viral: ~half cases, mostly HBV/HCV, rare HAV; HEV serious in PREGNANCY; herpesvirus too. Non-viral: drugs(acetaminophen/NSAIDs/isoniazid/halothane/antidepressants), poisoning, hypoxic injury, malignant infiltration.
Presents: hepatic failure + encephalopathy. High mortality without transplant.
Morphology: Gross=SMALL SHRUNKEN (500-700g), loose wrinkled capsule, muddy-red/yellow necrosis (“acute yellow atrophy”), green bile staining. Micro: SUBMASSIVE=zones 3+2 wiped, collapsed reticulin, ORDERLY regeneration (may restore architecture). MASSIVE=entire lobules necrotic, only reticulin+portal tracts+bile-plugged ductules left, scanty inflammation, DISORDERLY regeneration, fibrosis usually ABSENT.
Vaccines
HAV: passive(Ig)+active(killed vaccine). HBV: active recombinant vaccine — pre-exposure(high-risk groups, 3 doses 0/1/6mo) + post-exposure(Ig+vaccine combo). HDV: prevented BY HBV vaccine. HCV: NO vaccine yet. HEV: uncertain Ig protection, no vaccine yet.
Clinical relevance
IgM/IgG anti-HBc split (recent vs remote) + HBeAg→anti-HBe seroconversion (resolution prognostic) = highest-yield serology facts. HBV/HDV pathogenesis being IMMUNE-mediated (not direct cytopathic) = explains carrier state existing at all — same fact explains immunosuppressed patients tolerating chronic HBV “quietly” but clearing it poorly. HDV co-vs-superinfection = remember as “superinfection worse on EVERY axis,” not 5 separate facts. HCV’s mild-acute+high-chronicity signature = explains why it surpassed HBV as leading chronic liver disease cause globally. Fulminant hepatitis submassive-vs-massive maps directly to regeneration quality (orderly/architecture-preserving vs disorderly) = the reasoning behind differing prognosis.
Viral Hepatitis
Overview
Viral hepatitis is liver infection by hepatotropic viruses. Five main varieties, each producing a distinct type: HAV (faeco-oral, self-limiting), HBV (parenteral, may become chronic), HCV (previously “non-A, non-B”; chiefly transfusion-related), HDV (delta virus, superinfects HBV), HEV (water-borne). HBV is the only DNA virus among them; the rest are RNA viruses. A sixth type, hepatitis G, is also recognised etiologically. Other viruses (EBV, arboviruses causing yellow fever, CMV, herpes simplex) can affect the liver but produce nonspecific changes — the term “viral hepatitis” is reserved for the dedicated hepatitis viruses.
Hepatitis A
Caused by HAV — small (27 nm), icosahedral, non-enveloped, single-stranded RNA virus with a single serotype; can be cultivated in vitro and transmitted to primates; inactivated by boiling 1 min, UV, formaldehyde, or chlorine. Responsible for 20–25% of clinical hepatitis in developing countries, much lower in developed ones. Usually benign, self-limiting; incubation 15–45 days. Spreads almost exclusively faeco-orally, favoured by overcrowding/poor sanitation; contaminated frozen/stored food and water implicated in epidemics. Commonest age group 5–14 years; adults often infected from children. No chronic carrier state exists.
Pathogenesis: virus present in liver, bile, blood, stool during incubation and pre-icteric phase; viraemia/shedding diminish after jaundice onset. Immunologic basis evidenced by antibody markers: IgM anti-HAV appears at symptom onset; IgG anti-HAV appears after acute illness and persists indefinitely, giving lifelong protective immunity.
Hepatitis B
Caused by HBV (serum hepatitis) — DNA virus with longer incubation (30–180 days), transmitted parenterally (blood/blood products, IV drug use, dialysis, healthcare exposure) and by intimate contact (mother-to-child, sexual). Can occur at any age. Causes a broader spectrum of severe disease: acute hepatitis B, chronic hepatitis, progression to cirrhosis, fulminant hepatitis, and an asymptomatic carrier state; also has a role in hepatocellular carcinoma development.
Viral particles (electron microscopy of infected serum) — three forms, two sizes:
- Small particles (most numerous): 22 nm spheres and 22×100 nm tubules — excess viral envelope protein, i.e. HBsAg.
- Large particles (42 nm, Dane particles): double-shelled spheres, 100–1000× fewer than small particles — the intact virion.
Genome — 4 overlapping genes:
- S gene — surface envelope protein (HBsAg), the major protein. Pre-S1/pre-S2 regions upstream code for receptor and hepatocyte-membrane-binding proteins; S+pre-S2 = middle protein; pre-S1+pre-S2 = large protein (rich in complete virions).
- P gene — largest gene; codes DNA polymerase.
- C gene — codes two nucleocapsid proteins: HBeAg and core protein HBcAg.
- X gene — codes HBxAg, a small non-particulate protein with transactivation roles: signal transduction, increased HBV DNA replication, replication of other viruses (including HIV), enhanced cytolytic-T-cell susceptibility of infected hepatocytes, pro-apoptotic pathway. HBxAg/anti-HBx expression, via enhanced HBV DNA replication, is implicated in hepatocellular carcinoma in chronic hepatitis.
Pathogenesis — strong immune (not direct cytopathic) basis:
- A carrier state without hepatocellular damage exists → HBV itself is not directly cytopathic.
- Impaired cellular immunity → more persistent HBV disease instead of clearance.
- Cytotoxic CD8+ T lymphocytes attack viral nucleocapsid antigens (especially HBcAg, HBeAg) — supports cell-mediated damage.
- Variable CD8+ antiviral cytokine response across individuals determines recovery vs mild/severe/chronic disease.
Serologic/viral markers (sequential):
- HBsAg (originally “Australia antigen,” Blumberg 1965, Nobel Prize 1977) — appears ~6 weeks post-infection; marks active infection; usually disappears in 3–6 months; persistence >6 months = carrier state. Demonstrable in hepatocyte cell membranes of carriers/chronic hepatitis (Orcein stain, orange) but not during acute illness.
- Anti-HBs — appears late (~3 months post-onset), IgM and IgG; prevalence 10–15%; persists for life, confers protective immunity.
- HBeAg — transient (3–6 weeks) during acute attack; persistence beyond 10 weeks indicates chronic disease/carrier state development.
- Anti-HBe — appears after HBeAg disappears; seroconversion during acute illness is a good prognostic sign for resolution.
- HBcAg — not detectable in blood, but demonstrable in hepatocyte nuclei (Orcein) in carriers/chronic hepatitis, not during acute illness.
- Anti-HBc — detectable in serum during pre-icteric acute stage; IgM initially (persists 4–6 months, indicates recent infection), later IgG (indicates remote past infection).
- HBV-DNA — most sensitive index (Southern blot); present pre-symptomatically and transiently in early acute stage.
Hepatitis D
Infection with HDV in hepatocyte nuclei of HBsAg-positive patients. HDV is a defective virus requiring HBV as helper — hepatitis D only develops with concomitant HBV infection, either as co-infection (simultaneous) or superinfection (HDV infecting an existing chronic HBsAg carrier).
| Feature | Co-infection | Superinfection |
|---|---|---|
| Patient status | Healthy person | HBV carrier |
| Fulminant hepatitis risk | >HBV alone | >Co-infection |
| Chronic hepatitis risk | Rare | Much greater |
| Cirrhosis risk | Uncommon | More |
| Mortality | Rare | ~20% |
Superinfection (incubation 30–35 days) worsens chronic HBV infection — severe/fulminant acute attacks, progression of carrier state to chronic delta hepatitis, or accelerated cirrhosis; hepatocellular carcinoma is, however, less common in HBsAg carriers with HDV.
HDV is a small (36 nm), single-stranded RNA, double-shelled particle — outer shell HBsAg, inner shell delta antigen (circular RNA). Highly infectious in any HBsAg-positive host; replicates in hepatocyte nuclei. Markers: HDV in blood/liver nuclei, HDAg in blood/fixed tissue, anti-HD (IgM then lifelong IgG). Endemic in Southern Europe, Middle East, South India, parts of Africa; same high-risk groups as HBV.
Pathogenesis: unlike HBV, HDV is thought to be directly cytopathic — though some transmission cases from asymptomatic carriers suggest it is not always so.
Hepatitis C
Formerly “non-A, non-B” hepatitis, diagnosed by exclusion; now characterised as HCV. Acquired via blood transfusion/products, haemodialysis, parenteral drug abuse, accidental needle-pricks. ~90% of post-transfusion hepatitis is HCV. 1–2% of volunteer and up to 5% of professional blood donors carry HCV. Incubation 20–90 days (mean 50). Acute illness is milder than HBV, but HCV has a higher rate of progression to chronic hepatitis — persistence is the key feature. Cirrhosis after 5–10 years and progression to hepatocellular carcinoma are late consequences. HCV is now considered the more important cause of chronic liver disease worldwide.
HCV is a single-stranded, enveloped RNA virus, 30–60 nm, ~3000 amino acid genome (5’ end, capsid region C, envelope regions E1/E2).
Markers:
- Anti-HCV IgG — three generations, each detecting progressively earlier (1st gen against C100-3, ~1-3 months; 2nd gen against C200/C33c, ~1 month earlier; 3rd gen against C22-3/NS-5, earliest).
- HCV-RNA (PCR) — confirms infection; detectable within days of exposure, well before anti-HCV, persists for infection duration.
Pathogenesis — cell-mediated immune mechanism: host lymphoid cells may be infected; HCV-activated CD4+ helper cells stimulate CD8+ T cells via cytokines; stimulated CD8+ cells elaborate antiviral cytokines against HCV antigens; stronger immune response correlates with recovery rather than chronicity; certain HLA alleles/innate immunity/NK cells modulate host response; a subset shows crossreactivity between HCV antigens and host anti-liver-kidney-microsomal (anti-LKM) autoantibodies, explaining autoimmune hepatitis–HCV overlap.
Hepatitis E
Enterically transmitted (previously “epidemic/enteric non-A non-B” hepatitis). Affects young/middle-aged individuals, primarily India, other Asian countries, Africa, Central America. Acquired via water-supply contamination (e.g. post-monsoon flooding); unlike HAV, no secondary person-to-person spread. High mortality in pregnant women, but otherwise self-limited with no chronic liver disease association.
HEV: single-stranded, 32–34 nm, icosahedral, non-enveloped; isolated from stool, bile, liver. Markers: anti-HEV IgM/IgG (both fall rapidly, no routine test available), HEV-RNA.
Contrasting Features of the Five Hepatitis Viruses
| Feature | Hepatitis A | Hepatitis B | Hepatitis C | Hepatitis D | Hepatitis E |
|---|---|---|---|---|---|
| Year identified | 1973 | 1965 | 1989 | 1977 | 1980 |
| Particle size | 27 nm | 42 nm | 30–60 nm | 35–37 nm | 32–34 nm |
| Genome | RNA, ss, linear | DNA, ss/ds | RNA, ss, linear | RNA, ss, circular | RNA, ss, linear |
| Morphology | Icosahedral, non-enveloped | Double-shelled, enveloped | Enveloped | Enveloped, replication-defective | Icosahedral, non-enveloped |
| Spread | Faeco-oral | Parenteral, close contact | Parenteral, close contact | Parenteral, close contact | Water-borne |
| Incubation | 15–45 d | 30–180 d | 20–90 d | 30–50 d (superinfection) | 15–60 d |
| Severity | Mild | Occasionally severe | Moderate | Occasionally severe | Mild |
| Chronic hepatitis | None | Occasional | Common | Common | None |
| Carrier state | None | <1% | <1% | 1–10% | Unknown |
| Hepatocellular carcinoma | No | + | + | ± | None |
| Prognosis | Excellent | Worse with age | Moderate | Acute good, chronic poor | Good |
Clinicopathologic Spectrum
Evidence linking HBV/HCV to the full clinicopathologic spectrum is stronger than for other hepatotropic viruses; typical pathologic changes across major viruses are largely similar. HAV/HEV cause no carrier state and no chronic hepatitis. Spectrum categories: carrier state, asymptomatic infection, acute hepatitis, chronic hepatitis, fulminant hepatitis — plus (separately) progression to cirrhosis and hepatocellular carcinoma association.
I. Carrier State
An asymptomatic individual harbouring and capable of transmitting infection, without manifest disease — two types: asymptomatic healthy carrier, and asymptomatic carrier with chronic disease. HAV/HEV never produce a carrier state. HBV causes the largest number of carriers worldwide; HDV superinfection more often causes progressive disease than an asymptomatic carrier state. Geographic variation in HBV carrier prevalence: <0.5% in US/Western Europe, 5–20% in Asian/tropical countries. ~2–3% of the general population carry HCV asymptomatically. Two vulnerability factors for HBV carrier state: early age at infection, impaired immunity — ~10% of infected adults become carriers vs 90% of infected neonates. Clinical recognition: HBsAg persisting >6 months.
Morphology: healthy HBV carriers may show no change, or finely granular ground-glass eosinophilic cytoplasm (HBsAg evidence); carriers with chronic disease may show chronic hepatitis or even cirrhosis.
II. Asymptomatic Infection
Incidentally detected (raised transaminases or antibody positivity) without symptoms.
III. Acute Hepatitis
The commonest consequence of all hepatotropic viruses — acute inflammatory involvement of the entire liver. Types A–E run a broadly similar clinical course with similar pathology. Four clinical phases:
- Incubation period — varies by virus (see table above); asymptomatic, but infectivity is highest in the last days.
- Pre-icteric phase — prodromal constitutional symptoms: anorexia, nausea, vomiting, fatigue, malaise, distaste for smoking, arthralgia, headache; low-grade fever may precede jaundice (especially HAV). Earliest lab evidence: elevated transaminases.
- Icteric phase — jaundice onset, constitutional symptoms diminish; dark urine (bilirubinuria), clay-coloured stools (cholestasis), pruritus (raised bile acids), weight loss, tender hepatomegaly discomfort. Diagnosis: deranged LFTs (bilirubin, transaminases, alkaline phosphatase, prolonged PT, hyperglobulinaemia) plus serology.
- Post-icteric phase — icteric phase lasts 1–4 weeks, followed by recovery in 2–12 weeks (more prolonged in HBV/HCV). Up to 1% develop fulminant hepatitis; 5–10% progress to chronic hepatitis. Carrier-state evolution as described (not in HAV/HEV).
Morphology: Gross — liver slightly enlarged, soft, greenish.
- Hepatocellular injury — most marked in zone 3 (centrilobular): mild injury shows ballooning degeneration (swollen, granular cytoplasm condensing around nucleus); more severe injury shows acidophilic degeneration — intensely eosinophilic cytoplasm, pyknotic nucleus extruded, leaving a necrotic acidophilic mass (Councilman/acidophil body, by apoptosis); dropout necrosis (isolated/small hepatocyte clusters lysing); bridging necrosis (most severe — bands of necrosis linking portal tract-to-central vein, central vein-to-central vein, or portal tract-to-portal tract; may progress to fulminant or chronic hepatitis).
- Inflammatory infiltrate — mononuclear cells, mainly portal tracts, may permeate lobules.
- Kupffer cell hyperplasia — reactive, phagocytosing cellular debris/bile pigment/lipofuscin.
- Cholestasis — usually not severe; intracytoplasmic bile pigment granules.
- Regeneration — lobular disarray from necrosis; surviving hepatocytes regenerate/hyperplasia; reticulin collapse leads to healing by fibrosis, distorting architecture.
Etiologic clues: HAV shows panlobular involvement with heavy inflammatory infiltrate compared to others; HCV causes milder necrosis with fatty change, portal lymphoid aggregates, and bile duct epithelial degeneration.
IV. Chronic Hepatitis
Defined as continuing/relapsing hepatic disease >6 months with symptomatic, biochemical, serologic, and histopathologic evidence of inflammation/necrosis. Mostly from HBV, HCV, and combined HBV-HDV; non-viral causes include Wilson’s disease, α1-antitrypsin deficiency, chronic alcoholism, drug injury, and autoimmune disease (autoimmune/lupoid hepatitis — positive antinuclear/anti-smooth-muscle/anti-mitochondrial autoantibodies and LE cell test, negative viral markers).
Older morphologic classification (chronic persistent vs chronic active/aggressive, ± chronic lobular) has been superseded, since morphologic subtype doesn’t reliably predict prognosis (disease severity fluctuates); impaired immunity and extremes of age at infection are the real vulnerability factors. Current classification uses etiology + hepatitis activity score.
Chronicity rates: HCV — 40–60% of adults, particularly progressive, may evolve to cirrhosis. HBV — 90% of infected infants, ~5% of adult cases. HDV superinfection — 10–40%. HAV/HEV — none.
Morphology (common to HBV/HCV):
- Piecemeal necrosis — periportal hepatocyte destruction at the limiting plate: necrosed periportal hepatocytes, interface hepatitis (expanded portal tract infiltrated by lymphocytes/plasma cells/macrophages), often with proliferating bile ductules.
- Portal tract lesions — inflammatory infiltrate (“triaditis”), proliferated bile ductules; chronic hepatitis C may additionally show lymphoid aggregates/follicles with reactive germinal centres and bile duct epithelial damage.
- Intralobular lesions — architecture generally retained in mild-moderate disease: focal necrosis/inflammation, scattered acidophilic bodies, Kupffer cell hyperplasia; more severe disease shows bridging necrosis; regenerative changes; chronic HCV shows moderate fatty change; chronic HBV shows scattered ground-glass hepatocytes (abundant cytoplasmic HBsAg).
- Bridging fibrosis — irreversible-damage marker: initial periportal fibrosis at interface-hepatitis sites gives the portal tract a stellate shape; progressive cases show bridging fibrosis (portal-to-portal or portal-to-central); end-stage shows dense collagenous septa destroying architecture, forming nodules — postnecrotic cirrhosis.
Grading (hepatitis activity index, Knodell/Ishak): combines necroinflammatory activity (periportal/piecemeal or bridging necrosis 0–4; intralobular necrosis 0–4/0–6; portal inflammation 0–4) and stage of fibrosis (0–6, with 6 = cirrhosis).
Clinical features: range from mild (persistent transaminitis, fatigue, malaise, anorexia) to hepatomegaly/tenderness/mild splenomegaly, to deranged coagulation/bilirubin/globulin/alkaline phosphatase. Circulating immune complexes (HBV/HCV) may cause immune complex vasculitis, glomerulonephritis, cryoglobulinaemia in a subset. Clinical features do not reliably correlate with biopsy morphology — course is unpredictable, from stable-for-years to rapid cirrhotic evolution. Long-standing HBV/HCV chronic infection can evolve to hepatocellular carcinoma.
V. Fulminant Hepatitis (Submassive to Massive Necrosis)
The most severe form of acute hepatitis — rapidly progressive hepatocellular failure. Two patterns: submassive necrosis (less rapid, up to 3 months) and massive necrosis (rapid, fulminant, 2–3 weeks).
Viral causes: acute viral hepatitis accounts for ~half of cases, mostly HBV and HCV, less often combined HBV-HDV, rarely HAV; HEV is a serious complication specifically in pregnancy; herpesvirus can also cause serious hepatitis. Non-viral causes: drug toxicity (acetaminophen, NSAIDs, isoniazid, halothane, antidepressants), poisonings, hypoxic injury, massive malignant hepatic infiltration.
Patients present with hepatic failure and hepatic encephalopathy; mortality is high without transplantation.
Morphology: Gross — small, shrunken liver (500–700 g), loose wrinkled capsule; diffuse/random lobar involvement, muddy-red/yellow necrosis (formerly “acute yellow atrophy”), green bile-staining patches. Micro:
- Submassive necrosis — large hepatocyte groups in zones 3 and 2 wiped out, collapsed reticulin framework; regeneration is more orderly, may restore normal architecture.
- Massive necrosis — entire lobules necrotic; only collapsed reticulin framework and portal tracts with bile-plugged proliferated ductules remain; scanty inflammation; regeneration (if any) is disorderly, forming irregular hepatocyte masses; fibrosis is generally not a feature.
Immunoprophylaxis and Vaccines
Best prophylaxis is preventing spread once the transmission route is identified (food/water, sexual, parenteral). Pre-testing for antibodies determines whether prophylaxis/vaccination is needed.
- Hepatitis A — passive immunisation (immune globulin) and active immunisation (killed vaccine) both available.
- Hepatitis B — earlier passive-only, now active recombinant HBsAg vaccine available. Pre-exposure prophylaxis for high-risk groups (healthcare workers, dialysis patients/staff, haemophiliacs, IV drug users): 3 IM doses at 0, 1, 6 months. Post-exposure prophylaxis for unvaccinated exposed persons: combined hepatitis B immune globulin + vaccine.
- Hepatitis D — prevented by the hepatitis B vaccine (since HDV needs HBV).
- Hepatitis C — no vaccine yet feasible, though anti-envelope antibodies have been developed.
- Hepatitis E — uncertain whether immune globulin protects; vaccine not yet developed.
Clinical Relevance
- The IgM-vs-IgG anti-HBc distinction (recent vs remote infection) and the HBeAg-to-anti-HBe seroconversion (prognostic marker for resolution) are the two serologic facts most directly tied to clinical decision-making and staging of infection — worth prioritising over memorising every marker in isolation.
- HBV/HDV pathogenesis being predominantly immune-mediated rather than directly cytopathic (evidenced by the carrier state itself) is the conceptual anchor for why immunosuppressed patients tolerate chronic HBV more “quietly” but clear it less effectively — the same fact explains both observations.
- The co-infection-vs-superinfection distinction for HDV is a compact, frequently tested comparison — remember it as “superinfection is worse across every axis” (fulminant risk, chronicity, cirrhosis, mortality) rather than five separate facts.
- HCV’s defining clinical signature — milder acute illness but much higher chronicity — is the single fact that explains why it, not HBV, is now the leading global cause of chronic liver disease despite HBV having historically higher case numbers.
- Fulminant hepatitis’s submassive-vs-massive distinction maps directly onto regeneration quality (orderly/architecture-preserving vs disorderly), which is itself the reasoning basis for differing prognosis between the two patterns.
Viral Hepatitis
Overview
Viral hepatitis is liver infection by hepatotropic viruses. Five main varieties, each producing a distinct type: HAV (faeco-oral, self-limiting), HBV (parenteral, may become chronic), HCV (previously “non-A, non-B”; chiefly transfusion-related), HDV (delta virus, superinfects HBV), HEV (water-borne). HBV is the only DNA virus among them; the rest are RNA viruses. A sixth type, hepatitis G, is also recognised etiologically. Other viruses (EBV, arboviruses causing yellow fever, CMV, herpes simplex) can affect the liver but produce nonspecific changes — the term “viral hepatitis” is reserved for the dedicated hepatitis viruses.
Hepatitis A
Caused by HAV — small (27 nm), icosahedral, non-enveloped, single-stranded RNA virus with a single serotype; can be cultivated in vitro and transmitted to primates; inactivated by boiling 1 min, UV, formaldehyde, or chlorine. Responsible for 20–25% of clinical hepatitis in developing countries, much lower in developed ones. Usually benign, self-limiting; incubation 15–45 days. Spreads almost exclusively faeco-orally, favoured by overcrowding/poor sanitation; contaminated frozen/stored food and water implicated in epidemics. Commonest age group 5–14 years; adults often infected from children. No chronic carrier state exists.
Pathogenesis: virus present in liver, bile, blood, stool during incubation and pre-icteric phase; viraemia/shedding diminish after jaundice onset. Immunologic basis evidenced by antibody markers: IgM anti-HAV appears at symptom onset; IgG anti-HAV appears after acute illness and persists indefinitely, giving lifelong protective immunity.
Hepatitis B
Caused by HBV (serum hepatitis) — DNA virus with longer incubation (30–180 days), transmitted parenterally (blood/blood products, IV drug use, dialysis, healthcare exposure) and by intimate contact (mother-to-child, sexual). Can occur at any age. Causes a broader spectrum of severe disease: acute hepatitis B, chronic hepatitis, progression to cirrhosis, fulminant hepatitis, and an asymptomatic carrier state; also has a role in hepatocellular carcinoma development.
Viral particles (electron microscopy of infected serum) — three forms, two sizes:
- Small particles (most numerous): 22 nm spheres and 22×100 nm tubules — excess viral envelope protein, i.e. HBsAg.
- Large particles (42 nm, Dane particles): double-shelled spheres, 100–1000× fewer than small particles — the intact virion.
Genome — 4 overlapping genes:
- S gene — surface envelope protein (HBsAg), the major protein. Pre-S1/pre-S2 regions upstream code for receptor and hepatocyte-membrane-binding proteins; S+pre-S2 = middle protein; pre-S1+pre-S2 = large protein (rich in complete virions).
- P gene — largest gene; codes DNA polymerase.
- C gene — codes two nucleocapsid proteins: HBeAg and core protein HBcAg.
- X gene — codes HBxAg, a small non-particulate protein with transactivation roles: signal transduction, increased HBV DNA replication, replication of other viruses (including HIV), enhanced cytolytic-T-cell susceptibility of infected hepatocytes, pro-apoptotic pathway. HBxAg/anti-HBx expression, via enhanced HBV DNA replication, is implicated in hepatocellular carcinoma in chronic hepatitis.
Pathogenesis — strong immune (not direct cytopathic) basis:
- A carrier state without hepatocellular damage exists → HBV itself is not directly cytopathic.
- Impaired cellular immunity → more persistent HBV disease instead of clearance.
- Cytotoxic CD8+ T lymphocytes attack viral nucleocapsid antigens (especially HBcAg, HBeAg) — supports cell-mediated damage.
- Variable CD8+ antiviral cytokine response across individuals determines recovery vs mild/severe/chronic disease.
Serologic/viral markers (sequential):
- HBsAg (originally “Australia antigen,” Blumberg 1965, Nobel Prize 1977) — appears ~6 weeks post-infection; marks active infection; usually disappears in 3–6 months; persistence >6 months = carrier state. Demonstrable in hepatocyte cell membranes of carriers/chronic hepatitis (Orcein stain, orange) but not during acute illness.
- Anti-HBs — appears late (~3 months post-onset), IgM and IgG; prevalence 10–15%; persists for life, confers protective immunity.
- HBeAg — transient (3–6 weeks) during acute attack; persistence beyond 10 weeks indicates chronic disease/carrier state development.
- Anti-HBe — appears after HBeAg disappears; seroconversion during acute illness is a good prognostic sign for resolution.
- HBcAg — not detectable in blood, but demonstrable in hepatocyte nuclei (Orcein) in carriers/chronic hepatitis, not during acute illness.
- Anti-HBc — detectable in serum during pre-icteric acute stage; IgM initially (persists 4–6 months, indicates recent infection), later IgG (indicates remote past infection).
- HBV-DNA — most sensitive index (Southern blot); present pre-symptomatically and transiently in early acute stage.
Hepatitis D
Infection with HDV in hepatocyte nuclei of HBsAg-positive patients. HDV is a defective virus requiring HBV as helper — hepatitis D only develops with concomitant HBV infection, either as co-infection (simultaneous) or superinfection (HDV infecting an existing chronic HBsAg carrier).
| Feature | Co-infection | Superinfection |
|---|---|---|
| Patient status | Healthy person | HBV carrier |
| Fulminant hepatitis risk | >HBV alone | >Co-infection |
| Chronic hepatitis risk | Rare | Much greater |
| Cirrhosis risk | Uncommon | More |
| Mortality | Rare | ~20% |
Superinfection (incubation 30–35 days) worsens chronic HBV infection — severe/fulminant acute attacks, progression of carrier state to chronic delta hepatitis, or accelerated cirrhosis; hepatocellular carcinoma is, however, less common in HBsAg carriers with HDV.
HDV is a small (36 nm), single-stranded RNA, double-shelled particle — outer shell HBsAg, inner shell delta antigen (circular RNA). Highly infectious in any HBsAg-positive host; replicates in hepatocyte nuclei. Markers: HDV in blood/liver nuclei, HDAg in blood/fixed tissue, anti-HD (IgM then lifelong IgG). Endemic in Southern Europe, Middle East, South India, parts of Africa; same high-risk groups as HBV.
Pathogenesis: unlike HBV, HDV is thought to be directly cytopathic — though some transmission cases from asymptomatic carriers suggest it is not always so.
Hepatitis C
Formerly “non-A, non-B” hepatitis, diagnosed by exclusion; now characterised as HCV. Acquired via blood transfusion/products, haemodialysis, parenteral drug abuse, accidental needle-pricks. ~90% of post-transfusion hepatitis is HCV. 1–2% of volunteer and up to 5% of professional blood donors carry HCV. Incubation 20–90 days (mean 50). Acute illness is milder than HBV, but HCV has a higher rate of progression to chronic hepatitis — persistence is the key feature. Cirrhosis after 5–10 years and progression to hepatocellular carcinoma are late consequences. HCV is now considered the more important cause of chronic liver disease worldwide.
HCV is a single-stranded, enveloped RNA virus, 30–60 nm, ~3000 amino acid genome (5’ end, capsid region C, envelope regions E1/E2).
Markers:
- Anti-HCV IgG — three generations, each detecting progressively earlier (1st gen against C100-3, ~1-3 months; 2nd gen against C200/C33c, ~1 month earlier; 3rd gen against C22-3/NS-5, earliest).
- HCV-RNA (PCR) — confirms infection; detectable within days of exposure, well before anti-HCV, persists for infection duration.
Pathogenesis — cell-mediated immune mechanism: host lymphoid cells may be infected; HCV-activated CD4+ helper cells stimulate CD8+ T cells via cytokines; stimulated CD8+ cells elaborate antiviral cytokines against HCV antigens; stronger immune response correlates with recovery rather than chronicity; certain HLA alleles/innate immunity/NK cells modulate host response; a subset shows crossreactivity between HCV antigens and host anti-liver-kidney-microsomal (anti-LKM) autoantibodies, explaining autoimmune hepatitis–HCV overlap.
Hepatitis E
Enterically transmitted (previously “epidemic/enteric non-A non-B” hepatitis). Affects young/middle-aged individuals, primarily India, other Asian countries, Africa, Central America. Acquired via water-supply contamination (e.g. post-monsoon flooding); unlike HAV, no secondary person-to-person spread. High mortality in pregnant women, but otherwise self-limited with no chronic liver disease association.
HEV: single-stranded, 32–34 nm, icosahedral, non-enveloped; isolated from stool, bile, liver. Markers: anti-HEV IgM/IgG (both fall rapidly, no routine test available), HEV-RNA.
Contrasting Features of the Five Hepatitis Viruses
| Feature | Hepatitis A | Hepatitis B | Hepatitis C | Hepatitis D | Hepatitis E |
|---|---|---|---|---|---|
| Year identified | 1973 | 1965 | 1989 | 1977 | 1980 |
| Particle size | 27 nm | 42 nm | 30–60 nm | 35–37 nm | 32–34 nm |
| Genome | RNA, ss, linear | DNA, ss/ds | RNA, ss, linear | RNA, ss, circular | RNA, ss, linear |
| Morphology | Icosahedral, non-enveloped | Double-shelled, enveloped | Enveloped | Enveloped, replication-defective | Icosahedral, non-enveloped |
| Spread | Faeco-oral | Parenteral, close contact | Parenteral, close contact | Parenteral, close contact | Water-borne |
| Incubation | 15–45 d | 30–180 d | 20–90 d | 30–50 d (superinfection) | 15–60 d |
| Severity | Mild | Occasionally severe | Moderate | Occasionally severe | Mild |
| Chronic hepatitis | None | Occasional | Common | Common | None |
| Carrier state | None | <1% | <1% | 1–10% | Unknown |
| Hepatocellular carcinoma | No | + | + | ± | None |
| Prognosis | Excellent | Worse with age | Moderate | Acute good, chronic poor | Good |
Clinicopathologic Spectrum
Evidence linking HBV/HCV to the full clinicopathologic spectrum is stronger than for other hepatotropic viruses; typical pathologic changes across major viruses are largely similar. HAV/HEV cause no carrier state and no chronic hepatitis. Spectrum categories: carrier state, asymptomatic infection, acute hepatitis, chronic hepatitis, fulminant hepatitis — plus (separately) progression to cirrhosis and hepatocellular carcinoma association.
I. Carrier State
An asymptomatic individual harbouring and capable of transmitting infection, without manifest disease — two types: asymptomatic healthy carrier, and asymptomatic carrier with chronic disease. HAV/HEV never produce a carrier state. HBV causes the largest number of carriers worldwide; HDV superinfection more often causes progressive disease than an asymptomatic carrier state. Geographic variation in HBV carrier prevalence: <0.5% in US/Western Europe, 5–20% in Asian/tropical countries. ~2–3% of the general population carry HCV asymptomatically. Two vulnerability factors for HBV carrier state: early age at infection, impaired immunity — ~10% of infected adults become carriers vs 90% of infected neonates. Clinical recognition: HBsAg persisting >6 months.
Morphology: healthy HBV carriers may show no change, or finely granular ground-glass eosinophilic cytoplasm (HBsAg evidence); carriers with chronic disease may show chronic hepatitis or even cirrhosis.
II. Asymptomatic Infection
Incidentally detected (raised transaminases or antibody positivity) without symptoms.
III. Acute Hepatitis
The commonest consequence of all hepatotropic viruses — acute inflammatory involvement of the entire liver. Types A–E run a broadly similar clinical course with similar pathology. Four clinical phases:
- Incubation period — varies by virus (see table above); asymptomatic, but infectivity is highest in the last days.
- Pre-icteric phase — prodromal constitutional symptoms: anorexia, nausea, vomiting, fatigue, malaise, distaste for smoking, arthralgia, headache; low-grade fever may precede jaundice (especially HAV). Earliest lab evidence: elevated transaminases.
- Icteric phase — jaundice onset, constitutional symptoms diminish; dark urine (bilirubinuria), clay-coloured stools (cholestasis), pruritus (raised bile acids), weight loss, tender hepatomegaly discomfort. Diagnosis: deranged LFTs (bilirubin, transaminases, alkaline phosphatase, prolonged PT, hyperglobulinaemia) plus serology.
- Post-icteric phase — icteric phase lasts 1–4 weeks, followed by recovery in 2–12 weeks (more prolonged in HBV/HCV). Up to 1% develop fulminant hepatitis; 5–10% progress to chronic hepatitis. Carrier-state evolution as described (not in HAV/HEV).
Morphology: Gross — liver slightly enlarged, soft, greenish.
- Hepatocellular injury — most marked in zone 3 (centrilobular): mild injury shows ballooning degeneration (swollen, granular cytoplasm condensing around nucleus); more severe injury shows acidophilic degeneration — intensely eosinophilic cytoplasm, pyknotic nucleus extruded, leaving a necrotic acidophilic mass (Councilman/acidophil body, by apoptosis); dropout necrosis (isolated/small hepatocyte clusters lysing); bridging necrosis (most severe — bands of necrosis linking portal tract-to-central vein, central vein-to-central vein, or portal tract-to-portal tract; may progress to fulminant or chronic hepatitis).
- Inflammatory infiltrate — mononuclear cells, mainly portal tracts, may permeate lobules.
- Kupffer cell hyperplasia — reactive, phagocytosing cellular debris/bile pigment/lipofuscin.
- Cholestasis — usually not severe; intracytoplasmic bile pigment granules.
- Regeneration — lobular disarray from necrosis; surviving hepatocytes regenerate/hyperplasia; reticulin collapse leads to healing by fibrosis, distorting architecture.
Etiologic clues: HAV shows panlobular involvement with heavy inflammatory infiltrate compared to others; HCV causes milder necrosis with fatty change, portal lymphoid aggregates, and bile duct epithelial degeneration.
IV. Chronic Hepatitis
Defined as continuing/relapsing hepatic disease >6 months with symptomatic, biochemical, serologic, and histopathologic evidence of inflammation/necrosis. Mostly from HBV, HCV, and combined HBV-HDV; non-viral causes include Wilson’s disease, α1-antitrypsin deficiency, chronic alcoholism, drug injury, and autoimmune disease (autoimmune/lupoid hepatitis — positive antinuclear/anti-smooth-muscle/anti-mitochondrial autoantibodies and LE cell test, negative viral markers).
Older morphologic classification (chronic persistent vs chronic active/aggressive, ± chronic lobular) has been superseded, since morphologic subtype doesn’t reliably predict prognosis (disease severity fluctuates); impaired immunity and extremes of age at infection are the real vulnerability factors. Current classification uses etiology + hepatitis activity score.
Chronicity rates: HCV — 40–60% of adults, particularly progressive, may evolve to cirrhosis. HBV — 90% of infected infants, ~5% of adult cases. HDV superinfection — 10–40%. HAV/HEV — none.
Morphology (common to HBV/HCV):
- Piecemeal necrosis — periportal hepatocyte destruction at the limiting plate: necrosed periportal hepatocytes, interface hepatitis (expanded portal tract infiltrated by lymphocytes/plasma cells/macrophages), often with proliferating bile ductules.
- Portal tract lesions — inflammatory infiltrate (“triaditis”), proliferated bile ductules; chronic hepatitis C may additionally show lymphoid aggregates/follicles with reactive germinal centres and bile duct epithelial damage.
- Intralobular lesions — architecture generally retained in mild-moderate disease: focal necrosis/inflammation, scattered acidophilic bodies, Kupffer cell hyperplasia; more severe disease shows bridging necrosis; regenerative changes; chronic HCV shows moderate fatty change; chronic HBV shows scattered ground-glass hepatocytes (abundant cytoplasmic HBsAg).
- Bridging fibrosis — irreversible-damage marker: initial periportal fibrosis at interface-hepatitis sites gives the portal tract a stellate shape; progressive cases show bridging fibrosis (portal-to-portal or portal-to-central); end-stage shows dense collagenous septa destroying architecture, forming nodules — postnecrotic cirrhosis.
Grading (hepatitis activity index, Knodell/Ishak): combines necroinflammatory activity (periportal/piecemeal or bridging necrosis 0–4; intralobular necrosis 0–4/0–6; portal inflammation 0–4) and stage of fibrosis (0–6, with 6 = cirrhosis).
Clinical features: range from mild (persistent transaminitis, fatigue, malaise, anorexia) to hepatomegaly/tenderness/mild splenomegaly, to deranged coagulation/bilirubin/globulin/alkaline phosphatase. Circulating immune complexes (HBV/HCV) may cause immune complex vasculitis, glomerulonephritis, cryoglobulinaemia in a subset. Clinical features do not reliably correlate with biopsy morphology — course is unpredictable, from stable-for-years to rapid cirrhotic evolution. Long-standing HBV/HCV chronic infection can evolve to hepatocellular carcinoma.
V. Fulminant Hepatitis (Submassive to Massive Necrosis)
The most severe form of acute hepatitis — rapidly progressive hepatocellular failure. Two patterns: submassive necrosis (less rapid, up to 3 months) and massive necrosis (rapid, fulminant, 2–3 weeks).
Viral causes: acute viral hepatitis accounts for ~half of cases, mostly HBV and HCV, less often combined HBV-HDV, rarely HAV; HEV is a serious complication specifically in pregnancy; herpesvirus can also cause serious hepatitis. Non-viral causes: drug toxicity (acetaminophen, NSAIDs, isoniazid, halothane, antidepressants), poisonings, hypoxic injury, massive malignant hepatic infiltration.
Patients present with hepatic failure and hepatic encephalopathy; mortality is high without transplantation.
Morphology: Gross — small, shrunken liver (500–700 g), loose wrinkled capsule; diffuse/random lobar involvement, muddy-red/yellow necrosis (formerly “acute yellow atrophy”), green bile-staining patches. Micro:
- Submassive necrosis — large hepatocyte groups in zones 3 and 2 wiped out, collapsed reticulin framework; regeneration is more orderly, may restore normal architecture.
- Massive necrosis — entire lobules necrotic; only collapsed reticulin framework and portal tracts with bile-plugged proliferated ductules remain; scanty inflammation; regeneration (if any) is disorderly, forming irregular hepatocyte masses; fibrosis is generally not a feature.
Immunoprophylaxis and Vaccines
Best prophylaxis is preventing spread once the transmission route is identified (food/water, sexual, parenteral). Pre-testing for antibodies determines whether prophylaxis/vaccination is needed.
- Hepatitis A — passive immunisation (immune globulin) and active immunisation (killed vaccine) both available.
- Hepatitis B — earlier passive-only, now active recombinant HBsAg vaccine available. Pre-exposure prophylaxis for high-risk groups (healthcare workers, dialysis patients/staff, haemophiliacs, IV drug users): 3 IM doses at 0, 1, 6 months. Post-exposure prophylaxis for unvaccinated exposed persons: combined hepatitis B immune globulin + vaccine.
- Hepatitis D — prevented by the hepatitis B vaccine (since HDV needs HBV).
- Hepatitis C — no vaccine yet feasible, though anti-envelope antibodies have been developed.
- Hepatitis E — uncertain whether immune globulin protects; vaccine not yet developed.
Clinical Relevance
- The IgM-vs-IgG anti-HBc distinction (recent vs remote infection) and the HBeAg-to-anti-HBe seroconversion (prognostic marker for resolution) are the two serologic facts most directly tied to clinical decision-making and staging of infection — worth prioritising over memorising every marker in isolation.
- HBV/HDV pathogenesis being predominantly immune-mediated rather than directly cytopathic (evidenced by the carrier state itself) is the conceptual anchor for why immunosuppressed patients tolerate chronic HBV more “quietly” but clear it less effectively — the same fact explains both observations.
- The co-infection-vs-superinfection distinction for HDV is a compact, frequently tested comparison — remember it as “superinfection is worse across every axis” (fulminant risk, chronicity, cirrhosis, mortality) rather than five separate facts.
- HCV’s defining clinical signature — milder acute illness but much higher chronicity — is the single fact that explains why it, not HBV, is now the leading global cause of chronic liver disease despite HBV having historically higher case numbers.
- Fulminant hepatitis’s submassive-vs-massive distinction maps directly onto regeneration quality (orderly/architecture-preserving vs disorderly), which is itself the reasoning basis for differing prognosis between the two patterns.
Viral Hepatitis
- Sequential serologic marker timeline for acute hepatitis B (HBsAg → anti-HBs, HBeAg → anti-HBe, IgM anti-HBc → IgG anti-HBc)
- HDV co-infection vs superinfection outcome comparison, side by side
- Acute hepatitis’s four clinical phases (incubation/pre-icteric/icteric/post-icteric) as a timeline with key lab/symptom markers at each stage
- Chronic hepatitis progression ladder: piecemeal necrosis → interface hepatitis → bridging fibrosis → postnecrotic cirrhosis
Viral Hepatitis
- Sequential serologic marker timeline for acute hepatitis B (HBsAg → anti-HBs, HBeAg → anti-HBe, IgM anti-HBc → IgG anti-HBc)
- HDV co-infection vs superinfection outcome comparison, side by side
- Acute hepatitis’s four clinical phases (incubation/pre-icteric/icteric/post-icteric) as a timeline with key lab/symptom markers at each stage
- Chronic hepatitis progression ladder: piecemeal necrosis → interface hepatitis → bridging fibrosis → postnecrotic cirrhosis
My Sticky Notes
Personal revision notes, mnemonics and reminders.
