An Atypical Presentation of Epstein-Barr Virus Associated Infectious Mononucleosis Mistaken for Pyelonephritis.

Infectious mononucleosis, a syndrome characterized by the triad of pharyngitis, fever, and lymphadenopathy, is caused in the majority of cases by Epstein-Barr virus and usually presents in adolescents and young adults. The disease is for the most part self-limited with full recovery; however, life-threatening complications can occur. Manifestations of Epstein-Barr virus associated infectious mononucleosis can be variable and at times atypical, leading to a delay in diagnosis and consequently unnecessary tests and treatment. We present a case of infectious mononucleosis from Epstein-Barr virus in a female college student who was admitted to the hospital with the initial diagnosis of pyelonephritis. This diagnosis was made based on an abnormal urinalysis, including the presence of white blood cells, red blood cells, and protein, in the setting of high fevers, cough, abdominal pain, left costovertebral tenderness, and an unexplained left neck mass. A monospot was negative two days prior. Renal involvement in Epstein-Barr virus infection is not common and bridges the spectrum from asymptomatic urinary abnormalities to acute renal failure, with acute interstitial nephritis being the most frequent pathological finding. Our patient received corticosteroids and albuterol for a worsening cough, in addition to supportive care. Despite steroid therapy, she developed a debilitating, protracted urticarial rash, also thought to be caused by the Epstein-Barr virus infection. Our case highlights the varied and complex constellation of findings sometimes seen in Epstein-Barr virus infectious mononucleosis. Like in our patient, pharyngitis, a part of the hallmark triad of symptoms characterizing infectious mononucleosis, is not always present, and the monospot may be negative. A high degree of suspicion, as well as recognition that multiple organ systems may be involved in Epstein-Barr virus associated infectious mononucleosis, is required to make the proper diagnosis.