What are the differential diagnoses for acute fulminant hepatitis?

Differential Diagnoses for Acute Fulminant Hepatitis

The differential diagnosis of acute fulminant hepatitis must systematically exclude drug-induced liver injury (particularly acetaminophen), viral hepatitis (HAV, HBV, HCV, HEV, EBV, CMV), autoimmune hepatitis, Wilson's disease, and ischemic hepatitis, with hepatitis E and drug-induced injury being the most commonly missed diagnoses in clinical practice. 1, 2

Primary Differential Diagnoses (In Order of Clinical Frequency)

1. Drug-Induced Liver Injury (DILI)

• Most common cause in Western countries, particularly acetaminophen overdose 3
• Includes idiosyncratic drug reactions (minocycline, nitrofurantoin, infliximab) 4
• Critical pitfall: HEV infection misdiagnosed as DILI in 13% of cases 1
• Look for: medication history (including herbals), temporal relationship to drug exposure
• Serum acetaminophen levels are mandatory in all cases 5, 3

2. Viral Hepatitis

The most recent EASL guidelines 1 emphasize that all patients should be tested for HEV at presentation as first-line testing, not after other viruses are excluded:

• Hepatitis E (HEV): Now recognized as the commonest cause of acute viral hepatitis in many countries 1

  • Particularly severe in pregnant women (16% mortality vs 68% for other causes) 6
  • Often overlooked; test via serology AND PCR

• Hepatitis A (HAV): IgM anti-HAV 2, 3

• Hepatitis B (HBV): HBsAg and anti-HBc IgM 2, 3

  • Consider acute exacerbation of chronic HBV

• Hepatitis C (HCV): Anti-HCV may be initially absent; requires HCV RNA by PCR 2

• Non-hepatotropic viruses: EBV, CMV, HSV, VZV (especially in immunocompromised) 2, 7

  • Look for: extrahepatic symptoms (respiratory symptoms, lymphadenopathy)
  • Caution: Spurious low-level IgM reactivity for EBV/CMV can occur in AIH; confirm with PCR 2

3. Autoimmune Hepatitis (AIH)

• Presents as fulminant hepatitis in 6% of AIH cases 8
• Diagnostic challenge: 25-39% have normal IgG, 29-39% lack autoantibodies at presentation 8
• Histology shows: centrilobular hemorrhagic necrosis with lymphoplasmacytic infiltration, plasma cell clusters 8, 9
• CT finding: Heterogeneous hypoattenuated areas in 65% of fulminant AIH cases 8
• Management decision: If diagnosis uncertain after initial workup, institute short trial (≤2 weeks) of prednisolone 8

4. Wilson's Disease

• Must exclude in all patients <40 years with acute hepatitis 10
• Especially when acute hepatitis accompanied by rapid-onset jaundice + hemolytic anemia 10
• Tests required 10:
  • Serum ceruloplasmin (<0.1 g/L suggestive, but can be normal with inflammation)
  • 24-hour urinary copper (>1.6 μmol/24h)
  • Slit lamp exam for Kayser-Fleischer rings (absent in 50% with hepatic presentation)
  • Hepatic copper content (>4 μmol/g dry weight)
• Caution: Ceruloplasmin is an acute phase reactant and may be falsely normal with inflammation 10

5. Ischemic/Hypoxic Hepatitis

• Look for: hypotension, cardiac failure, shock 5, 2
• Characteristic pattern: massive AST/ALT elevation (often >1000s) with rapid decline
• Echocardiography and hepatic Doppler ultrasound are mandatory 5

6. Other Important Differentials

Acute presentations 1, 2:

• Acute fatty liver of pregnancy (can mimic HEV in pregnant women) 6
• Budd-Chiari syndrome (hepatic vein thrombosis)
• Acute alcohol-associated hepatitis
• Bile duct stones with acute cholangitis 2
• SARS-CoV-2 (added since 2019) 7

Metabolic/Infiltrative 2, 7:

• MASLD/MASH (usually lower transaminases, but can coexist with AIH)
• Malignant infiltration

Essential Diagnostic Workup Algorithm

Immediate Laboratory Testing 5, 2, 3:

1. Coagulation: PT/INR (defines ALF if ≥1.5)
2. Hepatic function: AST, ALT, alkaline phosphatase, bilirubin, albumin
3. Metabolic: Glucose (q2h monitoring), lactate, arterial blood gas, ammonia
4. Renal: Creatinine, electrolytes (maintain sodium 140-145 mmol/L)

First-Line Serological Testing 1, 2:

• Viral: HAV IgM, HBsAg, anti-HBc IgM, anti-HCV, HEV serology + PCR, HIV, EBV, CMV
• Autoimmune: ANA, ASMA, anti-LKM-1, IgG levels
• Toxicology: Serum acetaminophen, urine drug screen (amphetamine, cocaine)

Specialized Testing 2, 10:

• Wilson's disease workup (if age <40): ceruloplasmin, 24h urinary copper, slit lamp exam
• Coeliac disease: tissue transglutaminase antibodies (5-fold increased risk of acute hepatitis) 7

Imaging 5, 2:

• Hepatic Doppler ultrasound: mandatory to exclude vascular causes
• Echocardiography: assess cardiac function and volume status
• Unenhanced CT liver: if AIH suspected (heterogeneous hypoattenuated areas) 8
• MRCP: if jaundice, rigors, or very high alkaline phosphatase 2

Liver Biopsy 8, 2, 9:

• Mandatory for AIH diagnosis (unless contraindicated by coagulopathy/clinical instability)
• Minimum requirements: ≥1.5 cm length, ≥18G needle (preferably 16G), ≥6-8 portal tracts
• Transjugular approach if coagulopathy present
• Cannot reliably distinguish viral from autoimmune hepatitis histologically 9

Critical Clinical Pitfalls

1. Testing HEV only after other viruses are negative is outdated practice - test at presentation 1

2. Autoantibodies and hypergammaglobulinemia may be absent in 15-39% of fulminant AIH 8, 7

3. False-positive autoantibodies occur in 20% of viral hepatitis and other causes of massive necrosis 7, 9

4. Ceruloplasmin can be falsely normal in Wilson's disease with acute inflammation 10

5. Drug history must include herbals and over-the-counter medications 4

6. Polypharmacy in elderly increases risk of both DILI and HEV - test for both 1

7. Coeliac disease screening often forgotten but increases hepatitis risk 5-fold 7

Prognostic Assessment

Once diagnosis established, use King's College Criteria or MELD score for risk stratification and transplant evaluation 5, 3. Early contact with transplant center is mandatory for all cases with PT ratio <50% 5.