Final answer:
Erysipelas primarily affects the legs, often presenting as a raised, clearly bordered inflamed patch of skin due to infection by S. pyogenes. The condition can also occur on the face and is treated with antibiotics.
Step-by-step explanation:
Erysipelas is a skin condition that primarily affects the legs or face. It is characterized as a large, intensely inflamed patch of skin involving the dermis. The condition can manifest as a raised rash with clear borders, commonly on the lower extremities but can also present on the face. The infectious agent responsible for erysipelas is often Streptococcus pyogenes (S. pyogenes), which can enter the skin through tiny cuts or abrasions. Treatment typically involves antibiotics such as penicillin, as S. pyogenes generally has not developed widespread resistance to this drug. Moreover, proper identification of the particular pathogen is crucial for effective treatment.
Based on the information provided, erysipelas most commonly affects the legs (option 2), although the face is also a frequent site of infection.