Or erythema subitum, or Sixth disease. Dramatic viral rash. Caused by Herpesvirus 6 and 7.
Classically high fever, URTI symptoms or no focus, potentially febrile convulsion! Then rash appears as fever subsides, day 2-4.
Rash is widespread fine maculopapular, can be pale haloes around spots, mostly on trunk. Can be in mouth! Not itchy.