Potential Complications of Mononucleosis
The most critical complication of infectious mononucleosis is spontaneous splenic rupture, occurring in 0.1-0.5% of cases and representing a potentially life-threatening emergency, while other significant complications include airway obstruction from tonsillar enlargement, hepatitis, neurologic manifestations, and hematologic abnormalities. 1, 2
Life-Threatening Complications
Splenic Rupture
- Splenic rupture is the most feared complication, with a mortality rate of 9% when it occurs 2
- The average time from symptom onset to splenic rupture is 14 days, but cases have been reported up to 8 weeks after illness onset 2
- Men under 30 years of age within the first 4 weeks of symptom onset are at highest risk 2
- Abdominal pain is the presenting complaint in 88% of splenic rupture cases 2
- Importantly, 86% of splenic ruptures occur without any preceding trauma history, making this a truly spontaneous complication 2
- Only 73.8% of splenic injuries occur within the traditional 21-day activity restriction period, with 90.5% occurring within 31 days 3
Airway Obstruction
- Severe tonsillar enlargement can lead to upper airway obstruction requiring urgent intervention 1
- This represents an acute emergency requiring immediate recognition and management 1
Hematologic Complications
Blood Cell Abnormalities
- Hemolytic anemia can develop, though typically mild and self-limited 1
- Thrombocytopenia occurs in some patients and may contribute to bleeding risk 1
- Granulocytopenia can develop, potentially increasing infection susceptibility 1
Hepatic Complications
- Hepatomegaly occurs in approximately 10% of cases 1
- Mild hepatitis with elevated transaminases is common, though typically asymptomatic 1
- Severe hepatic dysfunction is rare but can occur 1
Neurologic Complications
Central Nervous System Involvement
- Encephalitis or meningoencephalitis can develop, though uncommon 1
- Guillain-Barré syndrome has been reported as a rare complication 4
- Seizures may occur in severe cases with CNS involvement 1
- Bell's palsy and other cranial nerve palsies can develop 1
Peripheral Nervous System
- Peripheral neuropathies may occur rarely 1
- Transverse myelitis has been documented as a rare complication 4
Cardiac Complications
- Myocarditis and pericarditis are occasionally encountered, though typically mild 4
- ECG abnormalities including ST segment changes and T wave abnormalities can occur even without clinical cardiac symptoms 4
Chronic Sequelae
Post-Infectious Fatigue
- Infectious mononucleosis is a recognized risk factor for chronic fatigue syndrome 1
- Fatigue may be profound initially but typically resolves within 3 months in uncomplicated cases 1
- A subset of patients develops persistent fatigue lasting beyond the acute illness 1
Immunologic Complications
Lymphoproliferative Disorders
- In immunocompromised patients, EBV infection carries increased risk of severe disease and lymphoproliferative disorders 5
- Hemophagocytic lymphohistiocytosis (hemophagocytic syndrome) can develop, particularly in patients on immunosuppressive therapy 4
- Post-transplant lymphoproliferative disorder is a concern in transplant recipients 4
Important Clinical Caveats
Risk Stratification
- Young males (particularly under age 30) require heightened vigilance during the first month of illness due to elevated splenic rupture risk 2
- Patients should be counseled that splenic rupture can occur without trauma and to seek immediate care for abdominal pain 2, 3
Activity Restrictions
- Given that substantial splenic injuries occur between 21-31 days after symptom onset, activity restriction should extend to at least 8 weeks rather than the traditional 3-4 weeks 2, 3
- Contact sports, heavy lifting, and vigorous activity should be avoided during this period 1, 2
- If return to high-risk activities is desired before 8 weeks, ultrasound should confirm resolution of splenomegaly 2