The Many Faces of Primary EBV Infection: A Case Series of Its Diverse Presentations.

Epstein-Barr virus (EBV) is distributed worldwide and shows a seroprevalence of over 90% in adults, while seroprevalence in children varies depending on geographic and socioeconomic factors. Although primary EBV infection (pEBV) is often asymptomatic in early childhood, infection later in life may present with a variety of symptoms, most commonly as infectious mononucleosis, though many other clinical manifestations may occur. We present four clinical cases to illustrate the diverse and uncommon manifestations of pEBV and to support diagnostic reasoning. The first case demonstrates a diagnostic challenge of pEBV in a patient with severe cholestatic hepatitis in the setting of a recent travel. The second case highlights bilateral eyelid swelling (Hoagland sign) as a potentially isolated early symptom of pEBV, which clinicians should consider within its broad differential diagnosis. In the third case, we emphasize the importance of clinical judgment in contrast to premature closure in the face of repeatedly negative EBV serologies and advocate for further diagnostic evaluation, such as PCR testing, when pEBV is strongly suspected. The fourth case describes a fatal outcome of pEBV late in life, complicated by hemophagocytic lymphohistiocytosis. Unusual presentations of pEBV may complicate the diagnostic process and may lead to unnecessary testing. Our case series underscores the broad clinical spectrum of pEBV and highlights key features that aid in distinguishing it from important differential diagnoses. Awareness of characteristic laboratory findings, including reactive lymphocytosis, elevated large unstained cells, persistent fever, and lymphadenopathy, splenomegaly, as well as mild-to-moderate hepatitis is essential for guiding a targeted diagnostic approach for pEBV.