Hepatitis C

1. Overview

• Robbins & Kumar Basic Pathology, p. 602
• Henry's Clinical Diagnosis and Management by Laboratory Methods

2. The Virus

Structure

• Highly conserved 5' and 3' untranslated regions (UTRs)
• A single large open reading frame (ORF) encoding a polyprotein of ~3000 amino acids

• Structural proteins: Core protein (nucleocapsid), E1 and E2 (envelope glycoproteins)
• Non-structural proteins: p7 (viroporin), NS2 (metalloproteinase), NS3 (serine protease + RNA helicase), NS4A (NS3 cofactor), NS4B (membranous web formation), NS5A (essential for virion assembly; also an interferon-resistance protein), NS5B (RNA-dependent RNA polymerase)

Genotypes

• Genotype 1a: Most common in North America
• Genotype 1b: Predominates in Europe; associated with fibrosing cholestatic hepatitis post-transplant
• Genotypes 4 and 5: Unique to Africa
• Genotypes 1 and 4: More resistant to interferon-based therapy (required 48 weeks vs. 24 weeks for genotypes 2/3)

• Yamada's Textbook of Gastroenterology, p. 1885-1886
• Henry's Clinical Diagnosis and Management by Laboratory Methods

3. Life Cycle

HCV lifecycle within a hepatocyte. Steps targeted by DAAs (protease inhibitors, NS5A inhibitors, RNA polymerase inhibitors) are marked. - Robbins & Kumar Basic Pathology, Fig. 14.11

1. Binding: HCV attaches to multiple hepatocyte surface receptors - CD81, claudin-1, scavenger receptor SR-B1, LDL receptor, and occludin
2. Endocytosis and fusion: Followed by uncoating and release of viral genome into the cytoplasm
3. Translation: The 5' internal ribosomal entry site (IRES) directs ribosomal translation of the polyprotein in the rough endoplasmic reticulum
4. Replication: NS5B RNA polymerase synthesizes a negative-strand RNA intermediate within ER-derived "membranous web" double-membrane vesicles, which then serves as template for new positive-strand genomes
5. Assembly: Core protein interacts with viral genomes at lipid droplets; E1/E2 envelope glycoproteins are incorporated with help of ApoE/B lipoprotein metabolism
6. Release: Mature virions are released from the hepatocyte

• Yamada's Textbook of Gastroenterology, p. 1886
• Robbins & Kumar Basic Pathology, p. 603

4. Epidemiology and Transmission

Global Burden

• ~170 million individuals affected worldwide
• ~2.7 million Americans with chronic HCV infection
• Annual new infections in the US dropped from >230,000 (mid-1980s peak) to ~17,000 - largely due to blood supply screening
• Recent resurgence linked to the opioid epidemic and injection drug use

Routes of Transmission

• Robbins & Kumar Basic Pathology, p. 601-602

5. Pathogenesis

• HCV-specific CD8+ cytotoxic T lymphocytes (CTLs) attack infected hepatocytes
• NS5A protein resists interferon signaling, aiding immune evasion
• The virus generates quasispecies variants that escape neutralizing antibodies, explaining why 90% of patients with chronic infection have detectable HCV RNA despite the presence of antibody
• Factors that accelerate fibrosis progression include: older age, male gender, alcohol use, immunosuppression, HBV/HIV coinfection, obesity, type 2 diabetes, metabolic syndrome, and insulin resistance
• Robbins & Kumar Basic Pathology, p. 602-603

6. Clinical Features

Incubation Period

Acute Hepatitis C

• ~85% of acute infections are asymptomatic and go unrecognized
• When symptomatic (20-30%): jaundice, anorexia, malaise, nausea, right upper quadrant pain, fatigue
• HCV RNA detectable in blood within 1-3 weeks of infection, coinciding with elevated serum transaminases (ALT/AST)
• Severe acute hepatitis is rare
• Spontaneous clearance occurs in only ~10-20% of cases

Chronic Hepatitis C

• Chronicity in 80-90% of infected individuals
• A characteristic feature is episodic elevations in serum aminotransferase separated by periods of normal enzyme levels
• Even patients with normal transaminases may sustain progressive liver damage and need treatment
• Cirrhosis develops in approximately 20% over 20-30 years
• Those with cirrhosis are at significant risk of hepatocellular carcinoma (HCC) - HCV accounts for ~1/3 of liver cancer cases in the US

Extrahepatic Manifestations

• Mixed cryoglobulinemia (vasculitis, purpura, arthralgia, glomerulonephritis)
• Membranoproliferative glomerulonephritis
• Porphyria cutanea tarda
• Lichen planus
• B-cell non-Hodgkin lymphoma
• Thyroid disease
• Robbins & Kumar Basic Pathology, p. 602-603
• Jawetz Melnick & Adelberg's Medical Microbiology 28E, p. 524-525

7. Diagnosis

Serological Testing

• Anti-HCV antibodies (3rd-generation ELISA): Detectable in 50-70% at symptom onset; in others, antibody appearance delayed 3-6 weeks. Antibodies target core, envelope, and NS3/NS4 proteins. Does not distinguish acute from chronic or resolved infection.
• In high-risk populations: positive predictive value >99%
• In low-risk populations (e.g., blood donors): positive predictive value only ~25%

Nucleic Acid Testing (NAT)

• Qualitative HCV RNA PCR: Confirms active viremia; positive within 1-2 weeks of infection (earlier than antibodies). Used to confirm active infection.
• Quantitative HCV RNA: Measures viral load (IU/mL by WHO standard); used to monitor treatment response. Real-time PCR has a detection range of 5 to 200 million IU/mL.
• HCV RNA is the primary test for confirming persistent infection in chronic hepatitis C
• As many as 15% of those with acute HCV infection can have transiently negative HCV RNA

Genotyping

• Nucleic acid-based assays used to genotype HCV
• Genotyping guides treatment regimen selection and duration

Liver Assessment

• Liver biopsy or non-invasive fibrosis scores (FIB-4, APRI) to stage fibrosis
• Elevated ALT/AST, with fluctuating pattern in chronic disease
• Henry's Clinical Diagnosis and Management by Laboratory Methods, p. 1545-1589
• Jawetz Melnick & Adelberg's Medical Microbiology 28E, p. 524

8. Treatment

Direct-Acting Antivirals (DAAs)

• Sofosbuvir/Velpatasvir (Epclusa) - pan-genotypic, once daily
• Glecaprevir/Pibrentasvir (Mavyret) - pan-genotypic, 8 weeks for treatment-naive non-cirrhotic
• Ledipasvir/Sofosbuvir (Harvoni) - genotypes 1, 4, 5, 6

Treatment Goal

Older Therapies (Largely Obsolete)

• Pegylated Interferon (PEG-IFN) + Ribavirin: The former standard of care. Major side effects included flu-like symptoms, depression, hemolytic anemia, neutropenia, thrombocytopenia, and significant teratogenicity. Ribavirin carries a black box warning for hemolytic anemia. These are no longer first-line.

Post-Liver Transplant Treatment

• Recurrent HCV post-transplant was a major concern leading to accelerated graft fibrosis
• DAA-based, interferon-free regimens have transformed outcomes in this population
• SVR after transplant prevents graft cirrhosis and markedly improves outcomes
• Fibrosing cholestatic hepatitis (FCH), a rare but severe form of recurrence (5-10% in some series), requires prompt reduction of immunosuppression plus antiviral therapy
• Henry's Clinical Diagnosis and Management by Laboratory Methods, p. 1548-1552
• Robbins & Kumar Basic Pathology, p. 603
• Sleisenger and Fordtran's Gastrointestinal and Liver Disease, p. 1886

9. Prevention

No Vaccine Available

• High mutation rate and quasispecies diversity
• Limited understanding of protective immunity
• Failure of neutralizing antibodies to prevent re-infection

Post-Exposure Prophylaxis

• Immunoglobulin is NOT recommended for HCV post-exposure prophylaxis - evidence is insufficient
• No antiviral post-exposure regimen is currently approved

Preventive Measures

• Screening of blood supply (has nearly eliminated transfusion-related HCV)
• Universal precautions for healthcare workers
• Harm reduction programs for injection drug users (needle exchange, opioid substitution therapy)
• Testing and treatment of infected individuals ("treatment as prevention")
• Yamada's Textbook of Gastroenterology, p. 1415-1422

10. Complications and Prognosis

• Robbins & Kumar Basic Pathology, p. 602-603
• Sleisenger and Fordtran's Gastrointestinal and Liver Disease, p. 1885-1886

Hepatitis C

Sources: Harrison's Principles of Internal Medicine 22E (2025) | Goldman-Cecil Medicine, International Edition

1. Definition and the Pathogen

• A 5' internal ribosome entry site (IRES) that mediates polyprotein translation
• A single open reading frame encoding a polyprotein of ~3000 amino acids
• A short 3' noncoding region involved in replication
• The RNA genome is encased in a protein core (nucleocapsid), surrounded by a lipid bilayer envelope containing two inserted viral glycoproteins (E1, E2) that mediate hepatocyte entry

• Structural: Core, E1, E2 (envelope glycoproteins), p7 (viroporin)
• Non-structural: NS2 (metalloproteinase), NS3 (serine protease + RNA helicase), NS4A (NS3 cofactor), NS4B (membranous web formation), NS5A (virion assembly; IFN-resistance), NS5B (RNA-dependent RNA polymerase - the replication engine)

Goldman-Cecil Medicine, Ch. 134

2. Epidemiology

Global Burden

• An estimated 8 million individuals are chronically infected worldwide (Goldman-Cecil)
• HCV causes approximately 290,000 deaths per year globally
• In the United States, ~2.4 million individuals are chronically infected (prevalence ~0.7%)
• HCV still causes more deaths in the US than HIV, largely because most cases remain undiagnosed

Geographic Prevalence

Routes of Transmission

Goldman-Cecil Medicine, Ch. 134

3. Pathobiology

Viral Entry

Replication

Immune Evasion and Chronicity

• A qualitatively and quantitatively deficient CD4+ T-helper and CD8+ CTL response that fails to clear infection
• NS5A protein inhibits multiple steps of the JAK-STAT interferon signaling pathway
• Continuous generation of quasispecies variants that escape neutralizing antibodies
• Patients who spontaneously recover and maintain anti-HCV antibodies are not protected against re-infection

Fibrogenesis

Goldman-Cecil Medicine, Ch. 135

4. Clinical Features

Acute Hepatitis C

• Acute HCV is most often asymptomatic and undiagnosed
• When symptomatic (minority): fatigue, anorexia, nausea, right upper quadrant discomfort, jaundice
• HCV RNA appears in serum within 1-2 weeks of infection
• ALT rises coinciding with peak viremia, then may fall
• Spontaneous clearance occurs in 20-50% of patients

Fig: Kinetics of HCV markers during acute, self-resolving hepatitis C. ALT = alanine aminotransferase; ULN = upper limit of normal. - Goldman-Cecil Medicine, Fig. 134-4

Chronic Hepatitis C

• Most cases are identified in asymptomatic patients (found incidentally on blood donation screening, insurance testing, or routine labs)
• The most common symptom is fatigue, which may persist for years
• ALT levels are characteristically episodic - fluctuating, with periods of near-normal values even during active hepatitis. Approximately one-third of patients have persistently normal aminotransferase activity
• Even patients with normal ALT may have hepatitis and fibrosis on biopsy and remain at risk for progression

Fig: Kinetics of HCV markers during acute hepatitis C that evolves toward chronic infection. Note the characteristic fluctuating ALT pattern. - Goldman-Cecil Medicine, Fig. 134-5

Extrahepatic Manifestations

• Low levels of circulating cryoglobulins (containing HCV RNA, anti-HCV, rheumatoid factor, low complement) found in 50-70% of chronic HCV patients
• Elevated rheumatoid factor in ~70%
• Fewer than 1% develop symptomatic cryoglobulinemic vasculitis: fatigue, myalgias, arthralgias, purpura, leukocytoclastic vasculitis, peripheral neuropathy, membranoproliferative glomerulonephritis

• Porphyria cutanea tarda
• Lichen planus
• Thyroid disorders
• B-cell non-Hodgkin lymphoma
• Diabetes mellitus (type 2)

Harrison's Principles of Internal Medicine 22E, Ch. 338; Goldman-Cecil Medicine, Ch. 135

5. Natural History and Complications

Harrison's Principles of Internal Medicine 22E, Ch. 338

6. Diagnosis

Screening Recommendations

Diagnostic Algorithm

• Detects exposure (past or present); does not distinguish acute, chronic, or resolved infection
• Positive result must be confirmed with HCV RNA

• Reflex testing on the same sample is recommended to improve linkage to care
• Confirms active viremia; detectable 1-2 weeks after infection (before antibodies appear)

Goldman-Cecil Medicine, Ch. 135; Harrison's Principles of Internal Medicine 22E, Ch. 338

7. Treatment

Goals of Therapy

• Durable suppression of HCV replication
• Reduced all-cause and liver-related mortality
• Regression of liver fibrosis
• Significantly reduced risk of hepatocellular carcinoma (though HCC surveillance must continue in those with established cirrhosis)

Who Should Be Treated?

The Interferon Era (1991-2013) - Historical Context

• IFN-α monotherapy (1991): SVR <10%
• IFN-α + ribavirin: SVR ~40%
• Pegylated IFN + ribavirin: SVR 55% overall; ~40% in genotypes 1/4 (48 weeks); >80% in genotypes 2/3 (24 weeks)
• First-generation protease inhibitors (telaprevir, boceprevir, 2011) + PEG-IFN/ribavirin: SVR ~65-75% in genotype 1

The DAA Era (2013-Present)

Current Recommended Pan-Genotypic Regimens (Harrison's 22E; Goldman-Cecil)

Acute Hepatitis C Treatment

• Treat all patients with 8 weeks of pan-genotypic oral DAA combination (sofosbuvir/velpatasvir OR glecaprevir/pibrentasvir)
• Although 20-50% spontaneously clear, immediate treatment is cost-effective and provides higher clearance rates

Re-treatment After Failure

• Glecaprevir/pibrentasvir or sofosbuvir/velpatasvir/voxilaprevir are approved for re-treatment
• Extension of treatment course or addition of ribavirin may be needed in cases with resistance-associated variants (RAVs) or cirrhosis
• Expert consultation is recommended after second treatment failure

Important Safety Considerations (Harrison's 22E)

• HBV reactivation warning: All DAAs carry a black-box warning - HBV reactivation can occur in HBsAg-positive patients (and, to a lesser extent, in isolated anti-HBc patients) when HCV is suppressed. Fatal fulminant hepatitis has been reported. HCV treatment should NOT be deferred because of HBV co-infection, but co-infection must be actively managed.
• Drug-drug interactions: Must be checked before initiating any DAA regimen (www.hep-druginteractions.org)
• General tolerability is excellent: headache and fatigue are the most frequently reported side effects

Harrison's Principles of Internal Medicine 22E, Ch. 196 and Ch. 338; Goldman-Cecil Medicine, Ch. 135 and Ch. 328

8. Prevention

No Vaccine Available

Post-Exposure Prophylaxis

• Neither immunoglobulin nor antiviral post-exposure prophylaxis is recommended
• Patients should be monitored with HCV RNA and ALT at baseline, week 2, and at 4 and 6 months after exposure
• Documented infection should be treated promptly with 8-week DAA therapy

Public Health Measures

• Universal screening of blood supply (risk now <1 in 2 million donations in the US)
• Harm reduction programs for injection drug use: needle and syringe exchange programs, opioid substitution therapy
• Universal precautions for healthcare workers
• Standard precautions for tattooing, piercing, acupuncture
• Breast-feeding is not contraindicated (unless cutaneous nipple lesions)
• Caesarean section is NOT recommended solely to prevent mother-to-infant transmission

Goldman-Cecil Medicine, Ch. 134

9. Prognosis

• Disease progression halts
• Fibrosis can partially reverse (even in advanced cases)
• Risk of HCC is markedly reduced (though not eliminated in established cirrhotics)
• Patients with compensated cirrhosis who achieve SVR still require lifelong HCC surveillance (ultrasound ± AFP every 6 months)
• Patients with decompensated cirrhosis may need liver transplantation even after SVR; however, DAA-based treatment post-transplant is highly effective and prevents graft cirrhosis from recurrent HCV

Harrison's Principles of Internal Medicine 22E, Ch. 338; Goldman-Cecil Medicine, Ch. 135

• Harrison's Principles of Internal Medicine, 22nd Edition (2025), McGraw Hill - Chapters 196, 338
• Goldman-Cecil Medicine, International Edition - Chapters 134, 135, 328