What is a common finding in patients with infectious mononucleosis caused by Epstein-Barr virus?

Infectious mononucleosis, primarily caused by the Epstein-Barr virus (EBV), is characterized by a significant immune response marked by a predominance of lymphocytes. This condition often leads to the proliferation of atypical lymphocytes, specifically reactive T-cells, in the peripheral blood. During an EBV infection, the body's immune system responds robustly, with a notable increase in the number of lymphocytes rather than the other types of white blood cells.

Lymphocytic predominance is a hallmark of infectious mononucleosis, contrasting with other infections where neutrophils might dominate the white blood cell response. This shift towards lymphocytes can help in diagnosing the condition, as other conditions may present differently. Detecting atypical lymphocytes can be an important part of identifying infectious mononucleosis and differentiating it from other disorders.

Thus, the presence of a lymphocytic predominance in the blood smear of a patient presenting with symptoms of mononucleosis is a classic finding, strongly correlating with the diagnosis of EBV infection.