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Larry M Baddour, MD, FIDSA
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Daniel J Sexton, MD
Sheldon L Kaplan, MD
Ted Rosen, MD
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Abena O Ofori, MD


Impetigo is a contagious superficial bacterial infection observed most frequently in children. It may be classified as primary impetigo (direct bacterial invasion of previously normal skin) (picture 1A-C) or secondary impetigo (infection at sites of minor skin trauma such as abrasions, minor trauma, and insect bites, or underlying conditions such as eczema (picture 2)). Pyoderma and impetigo contagiosa are sometimes used as synonyms for primary impetigo. The occurrence of secondary impetigo is sometimes referred to as "impetiginization."

Impetigo is most frequently observed in children ages two to five years, although older children of any age and adults may also be affected. The infection usually occurs in warm, humid conditions and is easily spread among individuals in close contact; risk factors include poverty, crowding, poor hygiene, and underlying scabies [1,2]. Carriage of group A Streptococcus (GAS) and Staphylococcus aureus predisposes to subsequent impetigo [3].


Variants of impetigo include non-bullous impetigo, bullous impetigo, and ecthyma. Poststreptococcal glomerulonephritis and rheumatic fever following impetigo have also been described. (See "Poststreptococcal glomerulonephritis" and "Acute rheumatic fever: Clinical manifestations and diagnosis".)

Non-bullous impetigo — Non-bullous impetigo is the most common form of impetigo. Lesions begin as papules that progress to vesicles surrounded by erythema. Subsequently they become pustules that enlarge and rapidly break down to form thick, adherent crusts with a characteristic golden appearance; this evolution usually occurs over about one week (picture 1A-B, 1D-E). Lesions usually involve the face and extremities. Multiple lesions may develop but tend to remain well localized. Regional lymphadenitis may occur, although systemic symptoms are usually absent.

Bullous impetigo — Bullous impetigo is a form of impetigo seen primarily in young children in which the vesicles enlarge to form flaccid bullae with clear yellow fluid, which later becomes darker and more turbid; ruptured bullae leave a thin brown crust (picture 1C, 1F-G) [4,5]. Usually there are fewer lesions than in non-bullous impetigo, and the trunk is more frequently affected. Bullous impetigo in an adult with appropriate demographic risk factors should prompt an investigation for previously undiagnosed human immunodeficiency virus (HIV) infection [6].


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Literature review current through: Sep 2016. | This topic last updated: Sep 11, 2016.
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