Acute maculopapular rash after febrile defervescence

Specialty: Pediatrics.

• Sudden rash
• sixth disease
• infantile roseola

Why it occurs

• Infection by Human Herpesvirus type 6 or HHV-6 (main etiological cause of roseola, a virus that infects ubiquitously in the first 2 years of life)
• Infection with Human Herpesvirus type 7 or HHV-7 (similar cause of sudden exanthema, typically presenting at slightly older ages)
• Enterovirus or adenovirus infections (can occasionally mimic the clinical pattern of high fever followed by a sudden rash when the fever subsides)
• Mild pharmacological reaction or drug rash (associated with the use of amoxicillin or other antibiotics administered erroneously during the febrile phase of the disease, confusing the diagnosis with an allergy to penicillin)

Initial workup

The diagnosis is eminently clinical based on the characteristic anamnesis (infant aged 6 to 18 months with high fever of 39-40 °C lasting 3 to 5 days, with excellent interictal general condition, which falls abruptly coinciding with the appearance of a pinkish, non-pruritic, erythematous maculopapular rash, located mainly on the trunk and neck, which disappears in 24-48 hours without peeling). Routine laboratory or serological testing is not recommended. In case of diagnostic doubt or complex seizures: Complete blood count, PCR, urine culture (to rule out urinary infection as a cause of the previous high fever) and lumbar puncture if there is suspicion of meningeal involvement.

Standard management

• Management of infantile roseola is purely symptomatic support. Paracetamol — analgesic and antipyretic of choice during the febrile phase to improve the comfort of the infant; dose of 10 to 15 mg/kg orally taken every 4-6 hours, not to exceed 60 mg/kg/day
• Ibuprofen — antipyretic alternative in people over 6 months; dose of 5 to 10 mg/kg orally taken every 6-8 hours, preferably administered with food
• No type of specific antiviral treatment is required (Ganciclovir or Foscarnet are reserved only for severely immunosuppressed patients with complications such as HHV-6 encephalitis) nor topical or systemic antihistamine treatments, since the rash is asymptomatic and self-limiting.