Cellulitis is tender, warm, erythematous, blanching plaques with ill-defined borders with occasional linear red macules proximal to the larger plaque. Application of pressure may produce pitting. A pre-existing puncture wound to the skin may be present. Septicemia may follow cellulitis in untreated patients. Periorbital cellulitis is of concern due to its potential for spread of infection to the brain. Complications of cellulitis include osteomyelitis, septic arthritis, thrombophlebitis, and bacteremia.

Erysipelas, also known as "St. Anthony's fire," is a form of cellulitis that is a deeper infection and is usually caused by beta-hemolytic streptococci. Patients have a prodrome of malaise, fever, and headache followed by an erythematous, indurated plaque with a sharply demarcated border and a "cliff-drop" edge. It primarily presents on the face. Untreated erysipelas can be serious due to vascular thrombosis, bacteremia, or toxin release.

Pathophysiology

Cellulitis can be due to many organisms. Notorious organisms include Staphylococcus aureus, Group A, B, C or G streptococci, S. pneumoniae, Haemophilus influenzae, or Escherichia coli. Dog and cat bites can lead to Pasteurella multocida infection, and human bites can lead to cellulitis due to Eikenella corrodens.

Treatment

Most patients are treated on an outpatient basis, however, children who are septic or have periorbital cellulitis need to be hospitalized for prompt, intravenous antibiotic therapy. Once the regional erythema, warmth, edema, and fever have decreased, treatment may be completed on an outpatient basis. Erysipelas usually improves within 48 hours of beginning antibiotic therapy.