Clinical meaning
Erysipelas is an acute bacterial infection of the upper dermis and superficial lymphatic system, distinguished from deeper cellulitis by its involvement of the superficial dermal layers and lymphatic vessels rather than the deeper subcutaneous tissue. The causative organism in the vast majority of cases (approximately 80%) is Group A beta-hemolytic Streptococcus (Streptococcus pyogenes), although Group B, C, and G streptococci can also cause the infection. Staphylococcus aureus is an uncommon cause of erysipelas but is a more frequent pathogen in cellulitis. Understanding the distinction between erysipelas and cellulitis is clinically important because it affects treatment decisions, prognosis, and patient education. The pathogenesis of erysipelas begins with bacterial entry through a break in the skin barrier. The most common portals of entry include skin trauma (abrasions, lacerations, insect bites), surgical wounds, fungal infections of the skin (tinea pedis or athlete's foot is a particularly important predisposing factor for lower extremity erysipelas), eczema, and venous stasis ulcers. Once the bacteria penetrate the epidermis, they invade the upper dermis and the superficial lymphatic vessels. Streptococcus pyogenes produces several virulence factors that facilitate tissue...