Diagnosis and Management of Infectious Mononucleosis
Diagnosis
This patient has infectious mononucleosis (IM) caused by Epstein-Barr virus (EBV), confirmed by the positive heterophile antibody test, and requires supportive care only—no antibiotics or antivirals are indicated. 1
The clinical presentation is classic for IM with:
- Sore throat and tonsillar erythema (pharyngitis) 2, 3
- Lymphadenopathy (axillary in this case, though cervical is more typical) 3, 4
- 14-day duration of symptoms 3
- Nausea (common systemic symptom) 2
- Positive heterophile antibody test (the "monospot" test) 1
Diagnostic Confirmation
A positive heterophile antibody test is diagnostic for EBV infection and no further EBV-specific testing is required. 1 The monospot test has 71-90% accuracy for diagnosing IM, though it can be falsely negative in up to 25% of cases during the first week of illness. 5 Since this patient has had symptoms for 14 days, the positive result is reliable. 1
If the heterophile test had been negative despite high clinical suspicion, you would need to perform EBV-specific serologic testing for IgG and IgM antibodies to viral capsid antigen (VCA) and antibodies to Epstein-Barr nuclear antigen (EBNA). 1, 6 Recent primary EBV infection shows VCA IgM positive with EBNA antibodies negative. 1
Why Not Streptococcal Pharyngitis?
While this patient has pharyngitis, antimicrobial therapy is of no proven benefit for acute pharyngitis except when caused by Group A streptococci. 2 The Infectious Diseases Society of America guidelines emphasize that EBV is a frequent cause of acute pharyngitis accompanied by generalized lymphadenopathy, which distinguishes it from typical streptococcal pharyngitis. 2 The 14-day duration and positive heterophile test confirm viral etiology, making bacterial testing unnecessary. 2, 7
Treatment Approach
Supportive Care (Mainstay of Treatment)
Treatment consists exclusively of symptomatic management with adequate hydration, analgesics, antipyretics, and rest guided by the patient's energy level. 3, 5
- Provide adequate hydration 3
- Use analgesics and antipyretics for symptom relief 3
- Allow activity level to be guided by patient's energy—do not enforce strict bed rest 3
- Advise that fatigue may persist for several months after acute infection resolves 3
What NOT to Use
Corticosteroids, acyclovir, and antihistamines are not recommended for routine treatment of infectious mononucleosis. 3 Corticosteroids should only be considered for respiratory compromise or severe pharyngeal edema. 3 Antivirals do not reduce the length or severity of illness. 5
Do not prescribe antibiotics—this is a viral infection and antibiotics provide no benefit while contributing to antimicrobial resistance. 2
Activity Restrictions
The patient must avoid contact sports and strenuous exercise for at least 4 weeks (some sources recommend 8 weeks) after symptom onset due to risk of splenic rupture. 3, 4 Splenic rupture occurs in 0.1-0.5% of patients and is potentially life-threatening. 4 Splenomegaly occurs in approximately 50% of IM cases. 4
Common Pitfalls to Avoid
- Do not prescribe amoxicillin or ampicillin—these antibiotics cause a characteristic maculopapular rash in 90% of IM patients and may lead to misdiagnosis of drug allergy. 3
- Do not rely solely on a negative heterophile test to rule out IM, especially early in illness (first week), as false-negative rates are high. 1, 5
- Do not allow return to sports before 4 weeks minimum, even if the patient feels better, due to splenic rupture risk. 3, 4
- Do not perform unnecessary EBV-specific antibody testing when the heterophile test is already positive. 1
Expected Clinical Course
Most patients have an uneventful recovery with spontaneous resolution. 4 Fatigue, myalgias, and need for sleep may persist for several months after the acute infection resolves. 3 The illness is generally benign and self-limited. 4