Non-antibiotic-Associated Petechial Rash in an Infectious Mononucleosis-Positive Patient: A Case Report.

Epstein-Barr virus (EBV) is the primary cause of infectious mononucleosis (IM). A cutaneous manifestation is typically observed after the administration of penicillin. We present a case of an otherwise healthy 18-year-old male patient with IM who developed a peripheral cutaneous petechial rash despite no recent exposure to penicillin. He exhibited classic signs of IM, including fever, fatigue, and pharyngitis. Ultrasound imaging demonstrated splenomegaly. He was confirmed to have IM via EBV antigen testing. Additional evaluation returned negative results for Chlamydia trachomatis, Neisseria gonorrhoeae, cytomegalovirus (CMV), human immunodeficiency virus (HIV), and Treponema pallidum. A complete blood count was within normal limits, effectively ruling out other potential causes of the rash. The rash was attributed to IM and resolved spontaneously within 10 days without treatment. In the absence of drug exposure or co-infection, an autoimmune mechanism may be implicated. This case underscores the need for further investigation into immune-mediated processes and suggests that the pathogenesis of IM may be more complex than previously understood.