Usually rapid course and very painful (out of proportion to appearance). Patient may or may not have entry site.
Other causes of severe cellulitis or necrotizing fasciitis are Haemophilus influenzae even if immunized. This is more common in children who are Inuit, Métis or First Nations. In these situations, adding cefuroxime IV to penicillin and clindamycin may be reasonable after appropriate cultures.
Consult with infectious diseases and surgery is recommended.
