A 20-year old male presents with fever, fatigue, posterior cervical lymphadenopathy, palatal petechiae and splenomegaly. Peripheral smeal shows atypical lymphocytes and heterophile antibody is positive. The likely diagonosis is -

Infections mononucleosis is a clinical syndrome characterised by pharyngitis ,cervical lymphadenopathy,fever, & lymphocytosis. Ut is most often caused by Epstein -Barr virus.Palatal petechiae,periorbital edema ,splenomegaly may occur. It is commonly seen in adolescence & young adulthood . Atypical lymphocyte are common in EB V infection . A heterophile antibody is present during the acute illness & convalescence which is detected by Paul-Bunnell or monospot test. Reference Harrison20th edition pg 987