ROSEOLA INFANTUM
Synonyms: Exanthem subitum Sixth disease
Key features
High fever followed by an exanthem at defervescence
Affects primarily infants and toddlers
Febrile seizures possible
Roseola infantum is a common febrile illness of infancy that is primarily caused by human herpesvirus-6 (HHV-6) infection and is occasionally associated with human herpesvirus-7 (HHV-7) infection (see Ch. 80). Most cases occur between age 6 months, when levels of protective maternal antibodies wane, and 3 years, with peak incidence at age 6–12 months. Between 40% and 80% of children are seropositive for HHV-6 by age 13 months, and most of the remainder by 3 years; however, less than a third of infections result in the classic clinical manifestations of roseola infantum. Roseola infantum occurs year-round but is most common in the spring; the incubation period is usually 9–10 days.
The characteristic presentation is a high fever (to 40–40.5°C; 104–105°F) for 3–5 days in an infant who otherwise appears well. Seizures occur during the febrile period in up to 10% of patients. Defervescence is accompanied by the appearance of rose-pink macules and papules on the trunk, neck, proximal extremities, and occasionally the face. Mild upper respiratory symptoms, injection of the tympanic membranes, cervical or occipital lymphadenopathy, edematous eyelids, and a bulging anterior fontanelle may also be present. An enanthem of red papules on the soft palate and uvula (Nagayama spots) can develop, and uvular and palatoglossal junctional ulcers represent a characteristic finding. The skin eruption typically fades over a few days. Nonspecific fevers with or without otitis media in infants may also be due to HHV-6 infection.
Additional pathogenic features and clinical manifestations of HHV-6 infection, including reactivation in the settings of immunosuppression and drug reaction with eosinophilia and systemic symptoms (DRESS) syndrome, are discussed in Chapter 80.