Renal enlargement associated with infectious mononucleosis.

A 5 1/2 year old boy developed severe infectious mononucleosis (I.M.) with fever and hepatitis persisting for eight weeks. The diagnosis of I.M. was confirmed serologically by the development of a heterophile antibody and an ox cell hemolysin. During the acute illness, bilaterally enlarged kidneys were noted by intravenous urography even though the patient had no significant clinical or laboratory evidence of renal disease. Fifteen months following discharge, clinical and laboratory findings were normal and the kidneys had decreased markedly in size.