Infectious mononucleosis, commonly known as the 'kissing disease,' primarily affects young adults aged 15-30. While children often experience a mild course, presenting as a typical respiratory infection, adults frequently develop a more severe clinical picture. This includes prolonged high fever, sore throat, significant malaise, muscle and joint pain, and headaches. Due to persistent high fever, enlarged lymph nodes, spleen, and liver, patients may repeatedly seek medical attention. This can lead to consultations with various specialists, such as hematologists for suspected lymphoma, or visits to emergency departments and ENT clinics for intractable fever and other symptoms.