Cellulitis is an acute diffuse spreading infection of the skin extending into the soft tissues. Erysipelas is an acute infection of the skin not extending into the soft tissues.
The main causative organisms are β-haemolytic Strep-tococci and Staph. aureus. Risk factors for development of cellulitis include damage to skin integrity (leg ulcer, traumatic wounds), venous insufficiency, leg oedema, diabetes and obesity. The mechanisms of infection are not clearly understood but may involve bacterial exotoxins and cytokine release.
Patients have a well-demarcated patch of erythema with swelling of the underlying soft tissues. There is warmth and tenderness to touch, often with local lymphadenopathy. If untreated, there is spreading of the erythema, abscess formation and secondary septicaemia. Systemic symptoms may include fever, fatigue and myalgia.
Abscess formation, septicaemia, toxic shock-like syn-drome.
The diagnosis is clinical; blood cultures should be taken but are usually negative.
Initial management with penicillin (Streptococcus) and flucloxacillin (Staphylococcus); erythromycin is useful for patients who are penicillin allergic. If the cellulitis is advanced or if it fails to respond to oral therapy, parenteral penicillin and flucloxacillin are used, and clindamycin, if penicillin allergic. It is useful to outline the erythema to allow the condition to be followed. Abscesses may require surgical drainage.