Internal Medicine

0521779407-10 CUNY1086/Karliner 0 521 77940 7 June 7, 2007 18:40

Impetigo 823

■Risk from exposure to other infected individuals, pets, spas, swim-

ming pools, dirty fingernails

■Risk increased with superficial cutaneous trauma. Recent epidemics

have been reported in football players at all levels and wrestlers.

■Often seen as a secondary complication in individuals with atopic

dermatitis, pediculosis capitis, herpes simplex (or zoster), scabies,

insect bites or contact dermatitis

■More frequent in temperate zones, summer months because of in-

creased heat and humidity

Signs and Symptoms

■may involve any body area, but most common one exposed surfaces

(i.e., face, hands, neck, extremities)

■begins as 1–2 mm red macules

■rapidly develops into either thin-roofed vesicles or bullae

■bullous variant from phage group II staphylococci; NOTE: Comm-

unity-acquired methicillin-resistant organisms have become

increasingly prevalent.

■vesiculopustular variant from beta-hemolytic streptococci (often in

combination with staphylococci)

■either variant prone to rupture of lesion with discharge of cloudy

fluid – subsequent formation of thick, honey-colored crust is hall-

mark of disease

■autoinoculation via scratching or fomites can lead to development

of satellite lesions

■mature lesions may clear centrally while remaining peripherally

active, giving an annular appearance

■fever and lymphadenopathy may develop in widespread disease

tests

Laboratory

■Basic studies: surface cultures can be useful if diagnosis in doubt,

also helpful when considering methicillin-resistant organisms

■Other tests: nares culture to determine Staph aureus

■carriage in recurrent cases

■Urinalysis: perform if nephritogenic strains of streptococci are

endemic in patient’s area

differential diagnosis

■Annular lesions may mimic tinea corporis (i.e., ringworm). KOH

preparation can be done if necessary.