We present a case of a 32-year-old white women, affected by breast cancer and treated with mastectomy, who underwent immediate breast reconstruction with a tissue expander. She presented a periprosthetic infection from Streptococcus pyogenes (group A streptococcus, GAS) after scarlet fever. S. pyogenes may be responsible for suppurative complications of the respiratory system and a variety of metastatic foci of infection such as suppurative arthritic, endocarditis, meningitis, or brain abscess. Even though, in the literature, several cases and types of infection associated with breast implantation have been described, to our knowledge this is the first case report of periprosthetic infection after scarlet fever. Signs, symptoms, diagnosis, and treatment of GAS infection that occurred 2 months after the surgery are discussed.