Snapshot A 6-month old boy born at full term to a 26-year-old mother is brought to the emergency room for high fevers and seizure lasting less than 1 minute. The mother reports that he has been healthy without any medical problems and has met all 6-month milestones. Two days ago, he began having high fevers and some irritability, and today, he had a seizure. He was admitted for infectious workup. The next day, his fever resolved and he developed a morbilliform blanching rash on his trunk. Introduction Classification human herpesvirus-6 (HHV-6) an enveloped, linear, double-stranded DNA virus transmission via respiratory secretions causes roseola infantum (exanthem subitum) Epidemiology demographics infants > children > adults location skin risk factors immunosuppression transplant recipients Pathogenesis the virus replicates in salivary glands the virus is latent in lymphocytes and monocytes may contribute to tumor progression in Kaposi sarcoma and lymphoma Associated conditions may be associated with human herpesvirus-7 Prevention no vaccines are available Prognosis does not commonly recur disease is self-limited Presentation Symptoms high fever for 3 days may have febrile seizures no upper respiratory symptoms Physical exam light pink morbilliform rash that develops after the fever resolves blanching discrete and irregular macules and papules lasts 2 days Nagayama spots erythematous papules on the mucosa of soft palate and uvula Studies Making the diagnosis based on clinical presentation Differential Measles distinguishing factor cough, conjunctivitis, coryza, Koplik spots, and confluent rash excluding palms and soles Rubella distinguishing factor post-auricular lymphadenopathy with non-confluent rash that desquamates Treatment Management approach mainstay of treatment is supportive care Conservative supportive care indication all patients modalities antipyretics hydration Complications Seizures