Complications of infectious mononucleosis

Chronic active EBV infection

The chronic form develops against the background of ongoing active virus replication and can last from one year to several years. Patients are troubled by persistent or recurrent symptoms resembling the acute phase of mononucleosis.

Clinical manifestations (sometimes acting as the only signs):

• Organ damage: involvement of the myocardium, kidneys, and central nervous system.
• Hemophagocytic syndrome: a severe immune-mediated condition.
• Prolonged low-grade fever: body temperature elevation of unknown origin.
• Secondary immunodeficiency: manifested by frequent bacterial, fungal, or mixed infections affecting the respiratory tract, gastrointestinal tract, skin, and mucous membranes.

To confirm the diagnosis of chronic infection, two criteria are required. First, acute mononucleosis must have occurred no more than 6 months prior to the patient's visit. Second, immunohistological proof of organ involvement is required — detection of the virus nuclear antigen using anticomplement immunofluorescence.

Delayed consequences: oncology and autoimmune processes

Even with asymptomatic replication of the virus (which is recorded in 15–20% of cases using PCR with a sensitivity of 10 copies per sample), a high risk of delayed complications remains. The virus persists in epithelial cells and B-lymphocytes.

Years and decades later, the following may develop:

1. Lymphoproliferative and oncological diseases: multiple polyclonal lymphomas, Burkitt lymphoma, nasopharyngeal carcinoma. The virus is also associated with gastric and intestinal cancer, as well as tongue and oral mucosal leukoplakia.
2. Autoimmune pathologies: systemic lupus erythematosus (SLE), rheumatoid arthritis, Sjögren's syndrome. A characteristic feature is their onset a long time after infection.
3. Chronic fatigue syndrome (CFS): the etiological role of the Epstein-Barr virus in the development of this symptom complex is currently being actively discussed.

Laboratory signs of a protracted course

Laboratory tests help suspect the transition of the infection into a protracted or atypical form. Initially, the diagnosis of typical mononucleosis relies on a hemogram (leukocytosis 10–20 × 10⁹/L, absolute lymphomonocytosis up to 90–95%) and the detection of atypical mononuclear cells (AM) in an amount of > 12%.

Atypical mononuclear cells are wide-cytoplasm basophilic lymphocytes with a large nucleus. In a classic course, they peak at the 2nd–3rd week and completely disappear by the beginning of the 4th month. If symptoms persist and certain serological markers are detected in the blood, a protracted course is diagnosed.

ELISA evaluation method (gold standard):

• anti-VCA IgM (antibodies to capsid antigen): appear early and normally disappear completely by the 6th month. However, their detection in high titers for longer than 3 months directly indicates a protracted course of the disease.
• anti-VCA IgG: reach a maximum by the second month and can be detected in low titers for about 2 years as a marker of past infection.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Morphology and Differential Diagnosis of Atypical Mononuclear Cells
• Interpretation of ELISA Serological Panel (VCA, EA, EBNA)
• Heterophile Antibody Tests (Paul-Bunnell and Hoff-Bauer Reactions)
• Pathogenesis of Hemophagocytic Syndrome in EBV Infection
• Differential diagnosis of mononucleosis-like syndrome

Other topics in the "Respiratory Infections" section

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