A college student seeks medical care for extreme fatigue and swollen lymph nodes in the neck. The WBC count is 11.3 *10⁹/L. The differential shows a relative and absolute lymphocytosis. Many of the lymphocytes are larger than normal, with a basophilic cytoplasm indented by the red blood cells (RBCs). The nuclei are less clumped than normal and some have nucleoli. The rest of the complete blood count (CBC) is normal. What is the most likely diagnosis?

Question

Quizplus · Accepted Answer

The symptoms and lab findings suggest infectious mononucleosis, which is caused by the Epstein-Barr virus (EBV) and characterized by extreme fatigue, swollen lymph nodes, relative and absolute lymphocytosis with atypical lymphocytes, and sometimes mild anemia and thrombocytopenia. The presence of atypical lymphocytes, which are larger and have abnormal nuclear features, is a hallmark of EBV infection. Infectious lymphocytosis is a milder form of lymphocytosis caused by other viruses, such as cytomegalovirus (CMV), and usually does not cause significant symptoms or atypical lymphocytes. Lymphoma and lymphocytic leukemia are less likely given the normal CBC and absence of other clinical features suggestive of malignancy.

A College Student Seeks Medical Care for Extreme Fatigue and Swollen