Infectious Mononucleosis

Infectious mononucleosis is an acute viral disease primarily caused by the Epstein — Barr virus (EBV). It is characterized by fever, pharyngeal involvement (acute tonsillitis), lymphadenopathy, hepatosplenomegaly, and the presence of atypical mononuclear cells in the peripheral blood.

The disease is most common in adolescents and young adults and is often transmitted via saliva, earning it the nickname “the kissing disease.” The virus itself does not directly trigger clinical manifestations; rather, it is the immune system that vigorously responds to infected B cells.

Etiology and pathophysiology

The causative agent is Epstein — Barr virus, a member of the Herpesviridae family. The virus enters the body through the mucosal surfaces of the oropharynx and infects B cells, inducing their active proliferation.

In response, the immune system generates a large number of T cells — specifically their сytotoxic T cells — tasked with eliminating the infected B cells. These reactive T cells are the “atypical mononuclear cells” that serve as a hematologic hallmark of the disease.

Clinical Significance

Clinical manifestations typically include the classic triad of symptoms:

• Fever. Body temperature may rise to 100.4–102.2 °F (38–39 °C) and persist for 1–2 weeks.
• Acute tonsillitis. Sore throat with enlarged, erythematous tonsils, often covered with extensive grayish-white exudate.
• Lymphadenopathy. Enlargement of lymph nodes, particularly in the posterior cervical region; nodes are firm and tender.

Additional findings often include splenomegaly and hepatomegaly. Diagnosis is based on clinical presentation, complete blood count (lymphocytosis with > 10 % atypical mononuclear cells), and serologic testing for EBV-specific antibodies.

Treatment is generally supportive: bed rest, adequate hydration, and antipyretics may be helpful. Due to the risk of splenic rupture, it is critical to avoid physical exertion for 3–4 weeks.

Differential Diagnosis

First and foremost, infectious mononucleosis must be differentiated from streptococcal pharyngitis. Unlike streptococcal infection, mononucleosis is marked by generalized lymphadenopathy, hepatosplenomegaly, and specific hematologic changes.