From the Guidelines
In mononucleosis, liver enzymes typically rise to 2-5 times the normal range, though they can occasionally increase to 10-20 times normal levels in severe cases. The severity of abnormal aminotransferase can be classified as mild: <5 times the upper reference limit, moderate: 5 to 10 times the upper reference limit, or severe: >10 times the upper reference limit, as discussed in the study by 1. The most commonly elevated enzymes are alanine aminotransferase (ALT) and aspartate aminotransferase (AST), which usually peak during the second or third week of illness.
- Normal ALT levels are 29 to 33 IU/L (0.48-0.55 mkat/L) in men and 19 to 25 IU/L (0.32-0.42 mkat/L) in women, as stated in the study by 1.
- These elevations occur because the Epstein-Barr virus (EBV) that causes mononucleosis can directly infect liver cells and trigger inflammation.
- Additionally, the immune response to the infection can cause collateral damage to liver tissue.
- Despite these sometimes dramatic elevations, serious liver damage is rare in mononucleosis, and enzyme levels typically return to normal within 3-4 weeks without specific treatment.
- Patients should avoid alcohol and medications that can stress the liver (like acetaminophen) during recovery.
- If liver enzymes exceed 10 times normal or jaundice develops, medical evaluation is important as this may indicate a more severe hepatic involvement requiring closer monitoring, as suggested by the classification of severity in the study by 1.
From the Research
Liver Enzyme Levels in Mononucleosis
- The levels of liver enzymes, such as aspartate transaminase (AST) and alanine transaminase (ALT), can be elevated in patients with infectious mononucleosis (IM) 2.
- A study found that 57% of patients with IM had abnormal AST levels, while 62% had abnormal ALT levels 2.
- The median time to resolution of liver function tests (LFTs) was 8 weeks, with a range of 6-12 weeks 2.
- Another study found that 57.4% of IM patients had elevated levels of both atypical lymphocytes and transaminase (ALT > 40 IU/L, AST > 45 IU/L) 3.
- A retrospective study of 695 children with IM found that 61 cases had elevated liver enzymes after clinical recovery, with asynchronous changes in AST and ALT present in 18 children 4.
Risk Factors for Liver Damage
- Elevated AST, lymphocyte percentage, and white blood cell count (WBC) were identified as risk factors for the development of liver injury in children with IM 4.
- School-aged children, those without myocardial injury, and those with elevated WBC, lymphocyte percentage, and AST should be monitored for potential liver damage 4.
- Careful evaluation is necessary following clinical recovery to determine if vaccination is appropriate 4.
Clinical Characteristics
- The clinical features of IM can vary with sex and age 4.
- Fever onset was more common in infancy, with 75.2% of cases occurring in this age group 4.
- The study found that children with IM who are school-aged, without myocardial injury, and have elevated WBC, lymphocyte percentage, and AST should be monitored for potential liver damage 4.