Case seriesPatient: Female, 24 • Male, 35Final Diagnosis: EBV-induced infectious mononucleosisSymptoms: Fever • general malaise • lymphadenopathyMedication: —Clinical Procedure: Physical examination and serological testingSpecialty: Infectious diseasesObjective:Rare co-existance of disease or pathologyBackground:Infectious mononucleosis is a clinical syndrome most commonly associated with primary Epstein-Barr virus (EBV) infection. In adults, the symptoms can often be severe and prolonged, sometimes causing serious complications. Analgesic or antipyretic drugs are normally used to relieve the symptoms. However, there is no causal treatment for the disease.Case Report:Two cases of adult patients with atopic predispositions developed nocturnal fever, general fatigue, pharyngitis and lymphadenopathy after an exacerbation of atopic symptoms or those of allergic rhinitis. Due to the positive results for EBV viral-capsid antigen (VCA) IgM and negative results for EBV nuclear antigen (EBNA) IgG, diagnoses of infectious mononucleosis induced by EBV were made in both cases. Although oral antibiotics or acetaminophen alone did not improve the deteriorating symptoms, including fever, headache and general fatigue, nonsteroidal anti-inflammatory drugs (NSAIDs), such as tiaramide or loxoprofen, completely improved the symptoms quickly after the initiation.Conclusions:In these cases, given the atopic predispositions of the patients, an enhanced immunological response was likely to be mainly responsible for the pathogenesis of the symptoms. In such cases, NSAIDs, that are known to reduce the activity of EBV, may dramatically improve the deteriorating symptoms quickly after the initiation. In the present cases, the immunosuppressive property of these drugs was considered to suppress the activity of lymphocytes and thus provide the rapid and persistent remission of the disease.