Snapshot A 70-year-old man presents with a pain on the side of his left foot. He has had long-standing tinea pedis of his left foot that did not respond to previous treatments. About a week ago, he noticed redness of his left foot. On physical exam, there is a 5 cm bright pink, warm, and tender well-demarcated plaque. He is given oral antibiotics. Introduction Clinical definition bacterial infection involving the upper dermis and cutaneous lymphatics often from S. pyogenes from superficial involvement of skin to deep impetigo (very superficial skin infection) erysipelas (upper dermis and cutaneous lymphatics) cellulitis (deeper dermis and subcutaneous tissues) Epidemiology demographics common in infants, children, and older adults risk factors existing skin injury lymphedema venous insufficiency diabetes hypertension prior streptococcal throat infection tinea pedis Etiology S. pyogenes most common S. aureus Pathogenesis pre-existing injury in skin can act as entry portal for bacteria Prognosis recurs in 10-40% of cases Presentation Symptoms painful and tense skin Physical exam well-defined bright pink and erythematous plaque raised above level of surrounding normal tissue clear line between involved and uninvolved tissue warm Studies Labs none needed Diagnosed clinically Differential Cellulitis deeper involvement of skin and soft tissues there is often an overlap and may not be distinguished clinically from cellulitis Treatment Conservative elevate affected area indications for all patients Medical penicillins indications for mild infection cephalosporins indications if there is contraindication to penicillin Complications Sepsis