Chapter 10 Cellulitis
PATHOPHYSIOLOGY
Cellulitis is an infection that affects the skin and subcutaneous tissue. The site of involvement is most commonly an extremity, but cellulitis may also occur on the scalp, the head, and the neck. Organisms causing cellulitis include Staphylococcus aureus, group A streptococci, and Streptococcus pneumoniae. Once common, invasive infection caused by Haemophilus influenzae type B is now rare as a result of childhood immunization. A history of trauma or, in young children, an upper respiratory tract infection or sinusitis, is often reported. The site of infection is characterized by a swelling with indistinct margins that is tender and warm. Infection may extend to deeper tissues or spread systemically. See Box 10-1 for orbital and periorbital cellulitis symptoms. Outcome is excellent with treatment.
