Infectious mononucleosis by Epstein-Barr virus: A complete laboratory picture

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).

Figure 1
Peripheral blood film in infectious mononucleosis by Epstein-Barr virus.

Infectious mononucleosis (IM) is associated with primary infection by Epstein–Barr virus (EBV), a gamma herpesvirus. The incubation period is about 30–50 days.¹

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.¹,²

A positive heterophile antibody test (monospot) has a sensitivity of 85 % and a specificity 94 %.¹

Aminotransferase levels may be elevated in adults.¹

The diagnosis of IM can be done by clinical presentation, the presence of atypical lymphocytes on a PBF, and a positive monospot.¹

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.¹

Treatment is supportive. Antiviral therapy is not recommended, and corticosteroids are only recommended for complicated cases.¹

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  Granted an ethical approval by the Ethical Commission of CAML.
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Data availability statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study.

REFERENCES

• ¹
  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.
• ²
  Bain BJ. Blood Cells: A Practical Guide. 6th ed. Wiley; 2022.

Publication Dates

• Publication in this collection
  01 July 2024
• Date of issue
  2024

History

• Received
  24 Sept 2023
• Accepted
  30 Oct 2023
• Published
  05 Dec 2023