Infectious Mononucleosis

Pei Lin, MD

Key Facts

Etiology/Pathogenesis

Epstein-Barr virus infection

Clinical Issues

Fever
Pharyngitis
Lymphadenopathy

Microscopic Pathology

Follicular and interfollicular hyperplasia
Range of cells from small mature forms to immunoblasts

Ancillary Tests

Proliferating lymphocytes in peripheral blood and lymphoid organs are largely CD3(+), CD8(+) T cells
Immunoblasts are CD30(+) and CD45(+)
EBV encoded early RNA (EBER) in situ hybridization highlights infected cells

Top Differential Diagnoses

Classical Hodgkin lymphoma
Peripheral T-cell lymphoma

Diagnostic Checklist

Symptom complex
Preserved overall architecture; marked follicular and interfollicular hyperplasia
Spectrum of small to large cells with many intermediate forms
No Reed-Sternberg cells or variants
Predominantly CD3(+),CD8(+) T cells
Positive serology or EBER

Epstein-Barr virus infection involving tonsil. Marked lymphoid hyperplasia with many tingible body macrophages, with focal karyorrhexis and exudate, are shown.

EBV lymphadenitis. Small to large lymphoid cells, eosinophils, and plasma cells are seen. The large cells

are immunoblasts with prominent nucleoli.

TERMINOLOGY

Abbreviations

Infectious mononucleosis (IM)

Synonyms

Epstein-Barr virus (EBV) lymphadenitis, Pfeiffer disease, glandular fever

Definitions

Acute lymphadenitis induced by EBV infection

ETIOLOGY/PATHOGENESIS

Infectious Agents

Epstein-Barr virus

CLINICAL ISSUES

Epidemiology

Age
- Mostly adolescents and young adults in USA
  - Even younger age in developing countries
Gender
- No gender preference

Presentation

Fever
Pharyngitis
Lymphadenopathy
Peripheral blood lymphocytosis of atypical lymphocytes

Laboratory Tests

Monospot test (a.k.a. heterophile antibody test)
EBV-specific antibody tests by immunofluorescence
- Elevated IgM antiviral capsid antigen (VCAs) and absence of antibodies to EBV nuclear antigen (anti-EBNA) indicate acute infection

Treatment

Options, risks, complications
- Observation is sufficient in most cases as disease resolves by itself
- Infection may be complicated by rupture of spleen or hepatitis

Prognosis