Roseola infantum, or exanthem subitum, is an acute viral illness marked by a high fever that characteristically resolves with the onset of the rash.

The majority of cases occur in children 6 months to 3 years and presents more often during the spring.

Roseola is caused by herpesvirus type 6 (HHV-6) that is spread via respiratory secretions.

The incubation period is 7 to 15 days before the onset of symptoms.

As with other herpesvirus infections, it is likely that HHV-6 establishes a latent infection after the acute illness. The isolation of HHV-6 from the saliva of healthy adults supports this view.

A prodrome of high fever for 3 to 5 days in an otherwise well child typically precedes the exanthem.

On occasion, the fever is accompanied by coryza, cough, headache, or abdominal pain.

The exanthem appears 1 day before to 1 day after defervescence and consists of discrete, “rose pink” macules or papules, 1 to 5 mm in diameter, often with a surrounding rim of pallor that frequently coalesce to form areas of confluent erythema (Fig. 7.6).

A widespread distribution is seen, with lesions appearing on the trunk, buttocks, neck, and, occasionally, the face and limbs.

The exanthem typically clears within 1 to 2 days, although it may persist for up to 10 days.

Occipital, cervical, and postauricular lymphadenopathy is commonly present.

Complications are uncommon and include seizures, encephalitis, and thrombocytopenia.

The characteristic clinical presentation is usually sufficient for diagnosis.

The diagnosis can be confirmed by detection of IgM to HHV-6 or a fourfold rise in IgG titers to the virus over time.