Virus (EBV)/Infectious Mononucleosis (IM)


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Infectious Mononucleosis (IM)


Brief facts

Anti EBV antibodies' titers

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Prevalence of symptoms and laboratory abnormalities

Based on Odumade OA, Hogquist KA, Balfour HH Jr. Progress and problems in understanding and managing primary Epstein-Barr virus infections. Clin Microbiol Rev. 2011 Jan;24(1):193-209.

Finding Prevalence (%) Comment
Pharyngitis 100 Occasionally seen without sore throat
Cervical (neck) lymphoadenopathy 95 Especially posterior and postauricular (behind the ear)
Fever 50 Flu-like, can be masked by antipyretic medications (for example, acetamenophen)
Hepatomegaly (enlarged liver) 25  
Splenomegaly (enlarged spleen) 33 Can result in splenic rupture during vigorous physical activity within 3 weeks of onset
Eyelid edema (puffiness of eyelids) 10 Unusual in other acute illnesses and highly specific to IM
Rash 5 Almost all patients given penicillin derivatives develop a rash
Transient palatal petechiae (small minor hemorrhages in mouth) 50  
Sore throat 95 Many patients describe this as the worst they ever had
Fatigue 90 Usually last symptom to resolve, can develop into Chronic Fatigue syndrome
Headache 75 Common but underappreciated
Body aches (myalgia) 50 Flu-like
Decreased appetite 50  
Abdominal discomfort 40 Due to mesenteric adenitis or hepatosplenomegaly
Alanine aminotransferase elevation (liver enzyme, reflects liver function) 80 5-10% of patients are jaundiced
Atypical lymphocytosis >10% 100 When a higher cut-off point is used to define abnormal number of atypical lymphocytes, the sensitivity decreases (i.e., more false-negative diagnoses) and the specificity increases (i.e., fewer false-positive diagnoses
Leukocytosis 40 Usually to increase in cytotoxic lymphocytes
Thrombocytopenia (decrease of platelets in blood) 25 Thought to be autoimmune
Anemia 10 Thought to be autoimmune
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Differential diagnosis

Based on Ebell MH. Epstein-Barr virus infectious mononucleosis. Am Fam Physician. 2004 Oct 1;70(7):1279-87.

Diagnosis Key distinguishing features
Acute human immunodeficiency virus (HIV) infection Mucocutaneous lesions, rash, diarrhea, weight loss, nausea, vomiting
Cytomegalovirus infection Paired IgG serology shows a 4-fold increase in antibody titers and a significant elevation in IgM (at least 30% of IgG value)
Streptococcal pharyngitis Absence of splenomegaly or hepatomegaly; fatigue is less prominent
Toxoplasmosis Paired IgG serology shows a 4-fold increase in antibody titers and a significant elevation in IgM (at least 30% of IgG value)
Other viral pharyngitis Adenopathy is less likely
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Potential complications

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