What is the difference between acute and chronic hepatitis?

Acute vs. Chronic Hepatitis: Key Distinctions

The fundamental difference between acute and chronic hepatitis is duration: acute hepatitis lasts up to 6 months from infection onset, while chronic hepatitis persists beyond 6 months with ongoing viral replication and liver inflammation. 1

Temporal Definition

Acute hepatitis is defined by:

• Duration of less than 6 months from initial infection 1
• Incubation period of 1-4 months between exposure and clinical presentation 1
• Potential for spontaneous viral clearance in 15-50% of cases within the first 6 months 1

Chronic hepatitis is characterized by:

• Persistence of infection beyond 6 months 1
• Ongoing viral replication with detectable HCV RNA or HBsAg for more than 6 months 1
• Less than 5% chance of spontaneous resolution once infection becomes chronic 1

Clinical Presentation Differences

Acute Hepatitis

• Frequently asymptomatic (60-80% of cases) 1
• When symptomatic: influenza-like syndrome, right upper quadrant pain, jaundice in approximately 30% of adults 1
• ALT levels typically exceed 7 times the upper limit of normal 1
• Age-dependent symptom expression: only 10% of children under 4 years develop symptoms versus 30% of adults over 30 years 1

Chronic Hepatitis

• Often clinically silent with minimal or no symptoms 1
• Diagnosed through persistent elevation of aminotransferases or histologic evidence of chronic inflammation 1
• Liver histology ranges from mild inflammation to active inflammation, fibrosis, cirrhosis, and hepatocellular carcinoma 1

Diagnostic Approach

For Acute Hepatitis

• Serologic confirmation required: IgM anti-HAV for hepatitis A, IgM anti-HBc plus HBsAg for hepatitis B 1
• Anti-HCV antibodies may be negative in early acute hepatitis C (only 50% positive at diagnosis) 1
• HCV RNA testing is essential when acute hepatitis C is suspected, as antibodies may not yet be detectable 1
• No role for molecular testing in diagnosing acute hepatitis B beyond pretransfusion screening 1

For Chronic Hepatitis

• Requires detection of both viral antibodies AND viral RNA/DNA (HCV RNA or HBsAg) 1
• Persistence of HCV RNA for more than 6 months confirms chronic infection 1
• Molecular assays play increasingly significant roles in chronic hepatitis B diagnosis and management 1
• Liver biopsy or non-invasive methods assess degree of inflammation and fibrosis 1

Progression Risk and Natural History

Hepatitis B

The probability of progression from acute to chronic infection is age-dependent 1:

• 90% chronicity rate with perinatal acquisition 1
• 25-30% chronicity rate in children under 5 years infected through household contacts 1
• Less than 10% chronicity rate after acute infection in adulthood 1

Chronic hepatitis B follows a paradigm of four phases: immune tolerance, immune clearance, inactive carrier state, and HBeAg-negative chronic hepatitis B, though not all patients progress through each phase 1

Hepatitis C

• 50-90% of acute hepatitis C cases progress to chronic infection 1
• Spontaneous clearance occurs in 15-50% within the first months, but rarely after several years 1
• Unlike hepatitis B, chronic hepatitis C does not present distinct immunological phases but represents a continuous process of persistent infection 2

Management Implications

Acute Hepatitis

• Hepatitis A and B: supportive care only, as no virus-specific treatments proven effective 3
• Acute hepatitis C: monitor HCV RNA for 12-16 weeks to detect spontaneous clearance before initiating treatment 1, 3
• If treatment indicated for acute hepatitis C, pegylated IFN-α monotherapy for 24 weeks achieves >90% viral eradication 1, 3

Chronic Hepatitis

• Chronic hepatitis B: antiviral therapy indicated for patients with elevated ALT, detectable HBV DNA, and significant liver inflammation/fibrosis 1
• Chronic hepatitis C: direct-acting antivirals (DAAs) with SVR rates exceeding 90% 1
• Requires regular monitoring: untreated patients assessed every 1-2 years with non-invasive methods 1, 3
• Patients with cirrhosis need HCC screening every 6 months indefinitely 1, 3

Critical Pitfall to Avoid

A common diagnostic challenge occurs in HBsAg-positive patients with jaundice: differentiating acute viral hepatitis B from acute exacerbation of chronic hepatitis B is difficult because both present similarly and IgM anti-HBc (traditionally a marker of acute infection) can appear during chronic hepatitis B exacerbations 4. This distinction is crucial because acute hepatitis B typically resolves spontaneously in 90-95% of adults, while acute exacerbation of chronic hepatitis B may lead to decompensation and warrants antiviral treatment 4.