An 8-month-old girl suddenly developed a high fever (103degF). Her pediatrician examined her and found no signs of upper respiratory tract infection, meningitis, or encephalitis. Two days later, the girl's fever reached 105degF and she suffered a febrile seizure. By the time the child was brought to the pediatrician's office, her temperature had dropped. The doctor noted a generalized papular rash. What was the doctor's most likely diagnosis for this child?

Roseola infantum caused by human herpes virus 6 (d) leads to seizures in 15% of symptomatic infants. In healthy infants, the infection is asymptomatic or follows the course described in the vignette. In immunocompromised children, the abrupt onset includes CNS and other organ system involvement. Following infection, the virus remains latent in lymphocytes and monocytes. Infection in adults or reactivation in adulthood may produce a mononucleosis-like syndrome with lymphadenopathy and hepatitis. In immunocompromised patients such as bone marrow, kidney, and liver transplant patients, much more serious infections/reactivations occur that may lead to organ rejection and death. Erythema infectiosum (a), hand-food-and-mouth disease (b), measles (c), and rubella (d) (caused by the viruses indicated in the choices) each present differently: "slapped cheek" reticular rash 7 to 10 days following a nonspecific prodrome; vesicles appearing on the hands, and disseminated maculopapular rashes beginning on the neck, respectively.