Skip to Main Content

6-23: Impetigo

Kanade Shinkai; Lindy P. Fox

ESSENTIALS OF DIAGNOSIS

ESSENTIALS OF DIAGNOSIS

  • Superficial blisters filled with purulent material that rupture easily.

  • Crusted superficial erosions.

  • Positive Gram stain and bacterial culture.

GENERAL CONSIDERATIONS

Impetigo is a contagious and autoinoculable infection of the skin (epidermis) caused by staphylococci or streptococci.

CLINICAL FINDINGS

A. Symptoms and Signs

The lesions consist of macules, vesicles, bullae, pustules, and honey-colored crusts that when removed leave denuded red areas (Figure 6–15). The face and other exposed parts are most often involved. Ecthyma is a deeper form of impetigo caused by staphylococci or streptococci, with ulceration and scarring (eFigure 6–47) that occurs frequently on the extremities.

eFigure 6–47.

Ecthyma, shown here, represents a deeper form of impetigo caused by Staphylococcus aureus or streptococci. (Used, with permission, from S Goldstein, MD.)

A photo illustrating ecthyma shows gray, scaly, and dry patches on a patient's leg.
View Full Size||Download Slide (.ppt)
Figure 6–15.

Typical honey-crusted plaque on the lip of an adult with impetigo. (Reproduced with permission from Richard P. Usatine, MD, in Usatine RP, Smith MA, Mayeaux EJ Jr, Chumley HS. The Color Atlas and Synopsis of Family Medicine, 3rd ed. McGraw-Hill, 2019.)

A patient with impetigo exhibits yellow, crusty plaques on the lower lip and just below the mouth.
View Full Size||Download Slide (.ppt)

B. Laboratory Findings

Gram stain and culture confirm the diagnosis. In temperate climates, most cases are associated with S aureus infection. Streptococcus species are more common in tropical infections.

DIFFERENTIAL DIAGNOSIS

The main differential diagnoses of honey-colored crusting are acute allergic contact dermatitis (eFigure 6–48) and herpes simplex. Contact dermatitis may be suggested by the history or by linear distribution of the lesions, and culture should be negative for staphylococci and streptococci. Herpes simplex infection usually presents with grouped vesicles or discrete erosions and may be associated with a history of recurrences. Viral cultures are positive.

eFigure 6–48.

A linear pattern of allergic contact dermatitis from poison ivy. Note the impressive line of vesicles where the leaf brushed the skin. (Reproduced with permission from Richard P. Usatine, MD, in Usatine RP, Smith MA, Mayeaux EJ Jr, Chumley HS. The Color Atlas and Synopsis of Family Medicine, 3rd ed. McGraw-Hill, 2019.)

A patient with contact dermatitis from poison ivy exhibits red patches with a series of tiny pustules over the skin of the forearm.
View Full Size||Download Slide (.ppt)

TREATMENT

Soaks and scrubbing can be beneficial, especially in unroofing lakes of pus under thick crusts. Topical agents, such as mupirocin, ozenoxacin, and retapamulin, are first-line treatment options for infections limited to small areas. In widespread cases, or in immunosuppressed individuals, systemic antibiotics are indicated. Cephalexin, 250 mg orally four times daily, is usually effective. Doxycycline, 100 mg orally twice daily, is a reasonable alternative. Community-associated methicillin-resistant S aureus (CA-MRSA) may cause impetigo, for which initial treatment may include doxycycline ...

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.

This site uses cookies to provide, maintain and improve your experience. MH Privacy Center Close