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Roseola Infantum

Roseola infantum (exanthem subitum, sixth disease) is caused by human herpes virus 6 (HHV-6), which is similar to cytomegalovirus. Two genotypes of HHV-6 (type A and type B) have been distinguished. As with other herpes viruses, HHV-6 shows persistent and intermittent or chronic shedding in the normal population, making the unusually early infection of children (seroconversion in the first year of life in up to 80% of all children) understandable. It is probably latent in salivary glands and blood. Virus may infect infants through the saliva mainly from mother to child. A severe, infectious mononucleosis-like syndrome in adults may be caused by a primary infection with HHV-6. HHV-6 has also been implicated in idiopathic pneumonitis in rosola.

Most cases are asymptomatic or present with fever of unknown origin and occur without a rash. The disease is sporadic, and the majority of cases occur between the ages of 6 months and 4 years.

Incubation period.

The incubation period of roseola infantum is 12 days, with a range of 5 to 15 days.

Prodromal symptoms.

There is a sudden onset of high fever of 103 to 106 F with few or minor symptoms. Most children appear inappropriately well for the degree of temperature elevation, but they may experience slight anorexia or one or two episodes of vomiting, running nose, cough, and hepatomegaly. Seizures (but more frequently general cerebral irritability) may occur before the eruptive phase. Most recover without sequelae.

Eruptive phase.

The rash begins as the fever subsides. The term exanthem subitum indicates the sudden "surprise" of the blossoming rash after the fall of the fever. Numerous pale pink, almond-shaped macules appear on the trunk and neck, become confluent, and then fade in a few hours to 2 days without scaling or pigmentation.

Laboratory evaluation.

Leukocytosis develops at the onset of fever, but leukopenia with a granulocytopenia and relative lymphocytosis appears as the temperature increases and persists until the eruption fades. Seroconversion during the convalescent phase can be detected with immunofluorescence or enzyme immunoassays.

Treatment.

Control temperature with acetaminophen.