Keywords:
Epstein-Barr virus; Infectious mononucleosis
A 36-year-old man presented to the emergency room with fever and fatigue for two weeks. Analytically showed: hemoglobin 143 g/L, platelet count 218 × 109/L, leukocytosis 17.5 × 109/L with lymphocytosis (81%), alanine aminotransferase 3.22 μkat/L, aspartate aminotransferase 2.13 μkat/L, lactate dehydrogenase 7.15 μkat/L, serologic testing for hepatitis B, C and HIV negative. Monospot test was positive.
The peripheral blood film (PBF) showed atypical lymphocytes (21% of leukocytes): (a) large lymphocytes with abundant and indented cytoplasm that surrounds red blood cells, with large nucleus some having central nucleoli; (b) sometimes with an apparent double cytoplasmic membrane; (c) large lymphocytes with a diffuse and reticular chromatin pattern and diffuse reticular cytoplasm; (d) large lymphocytes with strongly basophilic cytoplasm (plasmacytoid lymphocytes); (e) large to medium lymphocytes with large, medium and small uropods (thick and thin), some presenting microspikes or detached cytoplasm (hand-mirror cells); (f) medium to small lymphocytes with lobulated nucleus, sometimes occasionally resembling a cloverleaf; (g) large to medium granular lymphocytes; (h) apoptotic lymphocytes with regular vacuolated nucleus, and (i) band forms or hyposegmented neutrophils (pseudo-Pelger-Huët) with toxic granulations (Figure 1, Wright-Giemsa stain, × 100 objective).
Infectious mononucleosis (IM) is associated with primary infection by Epstein–Barr virus (EBV), a gamma herpesvirus. The incubation period is about 30–50 days.11 Luzuriaga K, Sullivan JL. Infectious mononucleosis [published correction appears in N Engl J Med. 2010 Oct 7;363(15):1486]. N Engl J Med. 2010;362(21):1993–2000. https://doi.org/10.1056/NEJMcp1001116.
https://doi.org/10.1056/NEJMcp1001116....
Atypical lymphocytes are activated T lymphocytes produced as part of the immunological response to EBV infected B lymphocytes. The presence of (a) ≥50 % lymphocytes in total leukocytes, and (b) ≥10 % atypical lymphocytes on PBF (sensitivity 75 %; specificity 92 %) are strongly suggestive of IM.11 Luzuriaga K, Sullivan JL. Infectious mononucleosis [published correction appears in N Engl J Med. 2010 Oct 7;363(15):1486]. N Engl J Med. 2010;362(21):1993–2000. https://doi.org/10.1056/NEJMcp1001116.
https://doi.org/10.1056/NEJMcp1001116....
,22 Bain BJ. Blood Cells: A Practical Guide. 6th ed. Wiley; 2022.
A positive heterophile antibody test (monospot) has a sensitivity of 85 % and a specificity 94 %.11 Luzuriaga K, Sullivan JL. Infectious mononucleosis [published correction appears in N Engl J Med. 2010 Oct 7;363(15):1486]. N Engl J Med. 2010;362(21):1993–2000. https://doi.org/10.1056/NEJMcp1001116.
https://doi.org/10.1056/NEJMcp1001116....
Aminotransferase levels may be elevated in adults.11 Luzuriaga K, Sullivan JL. Infectious mononucleosis [published correction appears in N Engl J Med. 2010 Oct 7;363(15):1486]. N Engl J Med. 2010;362(21):1993–2000. https://doi.org/10.1056/NEJMcp1001116.
https://doi.org/10.1056/NEJMcp1001116....
The diagnosis of IM can be done by clinical presentation, the presence of atypical lymphocytes on a PBF, and a positive monospot.11 Luzuriaga K, Sullivan JL. Infectious mononucleosis [published correction appears in N Engl J Med. 2010 Oct 7;363(15):1486]. N Engl J Med. 2010;362(21):1993–2000. https://doi.org/10.1056/NEJMcp1001116.
https://doi.org/10.1056/NEJMcp1001116....
If the diagnosis is unclear, EBV-specific serologic testing (testing for specific IgM and IgG antibodies against viral capsid antigens, early antigens, and EBV nuclear antigen proteins) can be used to a final diagnose.11 Luzuriaga K, Sullivan JL. Infectious mononucleosis [published correction appears in N Engl J Med. 2010 Oct 7;363(15):1486]. N Engl J Med. 2010;362(21):1993–2000. https://doi.org/10.1056/NEJMcp1001116.
https://doi.org/10.1056/NEJMcp1001116....
Treatment is supportive. Antiviral therapy is not recommended, and corticosteroids are only recommended for complicated cases.11 Luzuriaga K, Sullivan JL. Infectious mononucleosis [published correction appears in N Engl J Med. 2010 Oct 7;363(15):1486]. N Engl J Med. 2010;362(21):1993–2000. https://doi.org/10.1056/NEJMcp1001116.
https://doi.org/10.1056/NEJMcp1001116....
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Funding statementNone.
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Ethics of approval statementGranted an ethical approval by the Ethical Commission of CAML.
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Patient consent statementNot applicable.
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Permission to reproduce material from other sourcesNot applicable.
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Clinical trial registrationNot applicable.
Data availability statement
Data sharing is not applicable to this article as no new data were created or analyzed in this study.
REFERENCES
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1Luzuriaga K, Sullivan JL. Infectious mononucleosis [published correction appears in N Engl J Med. 2010 Oct 7;363(15):1486]. N Engl J Med. 2010;362(21):1993–2000. https://doi.org/10.1056/NEJMcp1001116.
» https://doi.org/10.1056/NEJMcp1001116. -
2Bain BJ. Blood Cells: A Practical Guide. 6th ed. Wiley; 2022.
Publication Dates
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Publication in this collection
01 July 2024 -
Date of issue
2024
History
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Received
24 Sept 2023 -
Accepted
30 Oct 2023 -
Published
05 Dec 2023