Sir.—I would like to mention an additional clinical feature of infectious mononucleosis not included by Drs Rapp and Hewetson in their comprehensive review article in the Journal (132:78-85, 1978). In 1967, Pullen et al1 first noted the high incidence (95%) of maculopapular rashes in patients with mononucleosis who received ampicillin. This observation in adult patients was corroborated in children by a retrospective multicenter study2 that showed that the characteristic exanthem developed in all 13 patients with infectious mononucleosis who received ampicillin.
Typically, the rash begins five to ten days after beginning ampicillin therapy. Macules and papules appear first on the trunk and after three to four days, the rash becomes generalized. Pruritus is freuqently present and is often severe. This exanthem usually persists for several days and sometimes resolves with desquamation.
This high incidence (693—100%) of morbiliform eruptions contrasts sharply with the natural presentation of