Roseola infantum (exanthem subitum)

Definition

Roseola infantum (exanthem subitum) is a viral infection of infants and young children caused by human herpesvirus 6B (HHV-6B), less commonly by HHV-7. It is characterised by high fever without localising signs, followed by a rash as the fever settles.

Occurrence & epidemiology

Children between 6 months and 3 years of age are most commonly affected; the disease is rare in adults. It is spread via saliva, typically from asymptomatic family members; the incubation period is about 5–15 days. It occurs most often in spring and autumn.

Clinical features

• Abrupt high fever (39.5–40.5 °C) for 3–5 days; despite the fever the child is usually alert. Cervical and posterior auricular lymphadenopathy often develops.
• As the fever falls rapidly, usually on the 4th day, a macular to maculopapular rose-pink rash appears, most prominent on the chest and abdomen and less so on the face and limbs; small blanching spots (2–5 mm), some with a pale halo, non-itchy and without blisters. It lasts from a few hours to 2 days.
• Similar spots on the soft palate and uvula (Nagayama spots).
• Febrile seizures in about 5–15% of young children; encephalitis or hepatitis are rare.
• In about 70% of HHV-6 infections the classic rash does not occur.

Diagnosis

• Clinical, based on the typical course in a child aged 6 months to 3 years: fever first, then the rash as the fever subsides.
• Laboratory tests are rarely needed; HHV-6 infection can be confirmed by serology or PCR, and quantitative PCR is mainly used to detect viral reactivation.

Differential diagnoses

• Measles
• Rubella (German measles)
• Kawasaki syndrome
• Scarlet fever
• Erythema infectiosum (fifth disease)
• Amoxicillin rash in infectious mononucleosis

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References (selection)

1. DermNet: Roseola (roseola infantum, exanthem subitum)
2. MSD Manual Professional: Roseola Infantum (Exanthem Subitum; Pseudorubella)

Cross-references