Roseola Infantum

Roseola infantum, also called exanthem subitum or sixth disease, is a self-limited febrile illness of infants and young children caused mostly by human herpesvirus 6B (HHV-6B), less often HHV-7 and HHV-6A, enteroviruses, and adenoviruses.

• Peak age 6 to 15 months; 90 percent of cases occur before age 2 years and almost all children are seropositive by age 3. Spread by saliva of asymptomatic adults; incubation 9 to 10 days; no seasonality.
• Features: abrupt high fever followed, as the fever falls, by a characteristic rash.
• Febrile seizures occur in about 10 to 15 percent of infected children (HHV-6 accounts for about a third of first febrile seizures in infants).
• Complications are uncommon: febrile seizures, encephalitis or encephalopathy, hepatitis, thrombocytopenic purpura, myocarditis; reactivation in immunocompromised and transplant recipients (pneumonitis, encephalitis, marrow suppression).
• Infectivity is highest during the febrile phase; shedding continues for life asymptomatically.

• Fever of 39.0 to 40.5 C for 3 to 5 days (sometimes up to 7 days), with a child that is comparatively well, active and feeding during the fever (disproportionately well for the temperature); irritability, mild coryza, decreased appetite, cervical or postauricular lymphadenopathy, eyelid oedema, bulging anterior fontanelle (benign), mild diarrhoea.
• Nagayama spots (red papules on the uvula and soft palate) in some.
• Rash begins as the fever resolves (within 12 to 24 hours): discrete 2 to 5 mm rose pink macules or maculopapules on the trunk, spreading to the neck, face and proximal limbs, non-pruritic, blanching, lasting 1 to 3 days (hours to days), fading without scaling or pigmentation; the child is well at the time of the rash.
• Red flags (consider serious infection): age under 3 months; fever with ill appearance; non-blanching rash; neck stiffness or bulging fontanelle with drowsiness; prolonged seizure, focal seizures, or persistent drowsiness; fever persisting beyond 5 to 7 days (Kawasaki disease, urinary tract infection, bacterial infection); respiratory distress; dehydration; immunocompromised child; rash occurring with fever (measles, rubella, scarlet fever, drug reaction).

• Clinical diagnosis, usually in retrospect when the rash appears after defervescence.
• During the febrile phase without a source, consider urinalysis and culture and other tests to exclude bacterial infection depending on age and appearance (full blood count, CRP, blood culture, lumbar puncture in young infants).
• HHV-6 PCR (blood, saliva) or IgM serology confirms but is rarely needed (reserved for atypical, immunocompromised, or severe neurological cases).
• Febrile seizure workup as indicated (glucose, urine, lumbar puncture in under 12 months or with meningism).
• Differentials: measles, rubella, enteroviral infection, adenovirus, scarlet fever, drug rash, Kawasaki disease, other viral exanthems, bacterial infection.

• Supportive: fluids and rest, light clothing, antipyretics for comfort: paracetamol 15 mg/kg orally every 4 to 6 hours (maximum 4 doses in 24 hours) or ibuprofen 5 to 10 mg/kg orally every 6 to 8 hours with food (age over 3 months and weight over 5 kg). Antipyretics do not prevent febrile seizures.
• No antibiotics are needed. No antiviral treatment in immunocompetent children.
• Febrile seizure first aid: place on side, do not restrain, call emergency services if the seizure lasts longer than 5 minutes (buccal midazolam 2.5 mg for 6 to 12 months, 5 mg for 1 to 4 years); reassure that febrile seizures are usually benign.
• Severe disease in immunocompromised patients (encephalitis, pneumonitis): ganciclovir 5 mg/kg intravenously every 12 hours (or foscarnet 60 mg/kg every 8 hours) by specialists, with renal monitoring and blood count.
• Isolation: children can return to nursery or school once fever has settled (24 hours without fever), since the rash is not infectious.
• Safety netting: return if the child is lethargic, has a stiff neck, non-blanching rash, seizure, fever beyond 5 days, poor drinking, or fewer wet nappies.
• Follow up is generally unnecessary; review at 1 to 2 weeks if there are complications or ongoing concerns.