Causes of Transaminitis
Transaminitis (elevated ALT and AST) results from hepatocellular injury with distinct etiologies depending on severity: for mild elevations (<5x upper limit), nonalcoholic fatty liver disease (NAFLD) is the predominant cause, while marked elevations (>1000 IU/L) are most commonly due to ischemic hepatitis (51% of cases).
Classification by Severity
The approach to transaminitis differs fundamentally based on the degree of elevation 1:
- Mild: <5 times upper reference limit
- Moderate: 5-10 times upper reference limit
- Severe: >10 times upper reference limit
Common Causes by Prevalence
For Mild Elevations (<5x Upper Limit)
The most frequent etiologies in primary care settings include 2:
- Nonalcoholic fatty liver disease (NAFLD) - affects up to 30% of the population and is the single most common cause
- Alcoholic liver disease - second most common
- Medication-induced liver injury (DILI) - including prescription drugs, over-the-counter medications, herbs, and supplements
- Viral hepatitis - hepatitis B and C
- Hereditary hemochromatosis
For Marked Elevations (>1000 IU/L)
The etiology distribution shifts dramatically with severe elevations 3:
- Ischemic hepatitis: 51% - by far the most common cause, associated with significantly higher mortality (odds ratio 21 compared to other causes)
- Drug-induced liver injury or toxins: 13%
- Viral hepatitis: 13.1%
- Pancreaticobiliary-related injury: 7.8% - notably, biliary pathologies can present with marked transaminase elevation despite traditionally being associated with cholestatic patterns
Uncommon and Rare Causes
Beyond the common etiologies, consider 2, 4:
Uncommon causes:
- Alpha-1 antitrypsin deficiency
- Autoimmune hepatitis
- Wilson disease
Extrahepatic sources:
- Thyroid disorders (hypothyroidism or hyperthyroidism)
- Celiac disease
- Hemolysis
- Muscle disorders (rhabdomyolysis)
Key Diagnostic Distinctions
ALT vs AST Specificity
ALT elevations are more specific for liver injury because ALT is concentrated primarily in hepatocytes, while AST can originate from heart, skeletal muscle, kidneys, brain, and red blood cells 1. Normal ALT levels are 29-33 IU/L in men and 19-25 IU/L in women.
Hepatocellular vs Cholestatic Pattern
Transaminitis specifically refers to hepatocellular injury with elevated aminotransferases. This differs from cholestatic patterns where alkaline phosphatase (ALP) predominates, though the 7.8% frequency of biliary causes in marked transaminitis demonstrates overlap 1, 3.
Critical Clinical Pitfall
The most important pitfall is missing ischemic hepatitis in patients with marked transaminase elevation. This carries a 21-fold higher mortality compared to other causes 3. Look for:
- Recent hypotensive episodes
- Cardiac failure or shock
- Respiratory failure
- Any condition causing hepatic hypoperfusion
The high mortality associated with ischemic hepatitis demands immediate recognition and treatment of the underlying circulatory compromise rather than focusing solely on the liver enzyme elevation itself.