MCQ – 88228

A 30-year-old man presents with a 1 week history of fever, sore throat, swollen lymph nodes, weight loss, and fatigue. Physical examination shows generalized lymphadenopathy, most prominent in the cervical lymph nodes, and mild hepatosplenomegaly. The peripheral blood smear shows 65% atypical lymphocytes. A Paul-Bunnell antigen test (heterophile antibody test) is positive. The serum ALT, AST, and bilirubin are slightly elevated. The atypical lymphocytes in this patient’s peripheral blood are described as which of the following?

A.	Activated T cells
B.	Immature B cells
C.	Mature B cells
D.	Natural killer cells

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Correct Answer � A Explanation

 Answer : A Activated T cells

The condition described in question is infectious mononucleosis.

It is characterized by fever, pharyngitis, lymphadenopathy, and circulating atypical lymphocytes. 

This systemic viral infection is caused by Epstein-Barr virus (EBV), a herpesvirus and is transmitted through respiratory droplets and saliva and binds to nasopharyngeal cells and B lymphocytes.

T cells proliferate in response to activated B lymphocytes and appear in the peripheral blood as atypical lymphocytes. Anemia and thrombocytopenia are common.

In developed countries, infectious mononucleosis commonly affects teenagers and young adults and is often referred to as the “kissing disease.”

 In underdeveloped countries, EBV infections are typically seen as subclinical infections in childhood and are associated with an increased risk of Burkitt lymphoma and nasopharyngeal carcinoma.

 Although EBV infects B cells, the circulating atypical lymphocytes seen in patients with infectious mononucleosis are not immature B cells, but rather indirectly activated T cells.