Impetigo and ecthyma

Published on 11/06/2015 by admin

Filed under Pediatrics

Last modified 22/04/2025

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Newborn with bullous impetigo. Flaccid, thin-roofed blisters and erosions involve the abdominal skin.

Impetigo in an infant. Crusts have spread from beneath the nose.

Impetigo. Diagnostic honey-colored crusts on skin above upper lip.

Ecthyma. Dry, firm crust surrounded by indurated border.

CLINICAL FEATURES

Moist, honey colored crusts are considered diagnostic of impetigo. Impetigo begins as tiny 1–3-mm vesicles with thin fragile roofs that evolve into moist crusts. The face, nose and extremities are the most frequent sites of involvement.

Bullous impetigo is the term used when large bullae surround central moist crust or form shallow erosions with a thin remnant of blister roof as an outer zone. This form is the predominant presentation in newborns. Whether blisters are large or small, impetigo is the preferred term.

S. aureus and streptococcus are responsible for the lesions of impetigo, with up to 50% of S. aureus due to MRSA in North America. Colonization of the skin occurs days to months before microscopic breaks in the skin permit the bacteria to invade. Poor hygienic habits such as nose-picking enhance the spread of impetigo. Nasal carriage of pathogenic bacteria is common. In a few children, nephritogenic strains of streptococcus have been responsible.

Ecthyma while due to the same bacteria, differs in clinical appearance from impetigo by the presence of indurated borders surrounding a firm, dry crust. Direct pressure on the crust produces purulent material to extrude from beneath the crust. Ecthyma represents involvement of entire epidermis whilst impetigo involves only the upper epidermis.