Which skin infection involves the upper dermis and superficial lymphatics and is classically associated with clear demarcated borders?

Which skin infection involves the upper dermis and superficial lymphatics and is classically associated with clear demarcated borders?

• A. Erysipelas
• B. Cellulitis
• C. Impetigo
• D. Folliculitis

Answer: (A)

Characterizing skin infections by depth of involvement and border clarity helps distinguish how they present. Erysipelas is a superficial skin infection that involves the upper dermis and the superficial lymphatics, producing a bright red, warm, and tender plaque with a clearly defined, sharp border. The involvement of lymphatics explains the raised, lemon-yellow-to-white edge and the rapid spread seen along lymphatic channels. It’s most commonly caused by group A Streptococcus. This contrasts with cellulitis, which penetrates deeper into the dermis and subcutaneous tissue and tends to have ill-defined, spreading margins rather than a crisp edge. Impetigo presents with superficial vesicles or pustules that rupture to form crusts, not a clearly demarcated inflamed plaque. Folliculitis is centered on hair follicles with localized pustules around a hair shaft, rather than a sharply bordered, diffuse patch of erythema.

Characterizing skin infections by depth of involvement and border clarity helps distinguish how they present. Erysipelas is a superficial skin infection that involves the upper dermis and the superficial lymphatics, producing a bright red, warm, and tender plaque with a clearly defined, sharp border. The involvement of lymphatics explains the raised, lemon-yellow-to-white edge and the rapid spread seen along lymphatic channels. It’s most commonly caused by group A Streptococcus.

This contrasts with cellulitis, which penetrates deeper into the dermis and subcutaneous tissue and tends to have ill-defined, spreading margins rather than a crisp edge. Impetigo presents with superficial vesicles or pustules that rupture to form crusts, not a clearly demarcated inflamed plaque. Folliculitis is centered on hair follicles with localized pustules around a hair shaft, rather than a sharply bordered, diffuse patch of erythema.