Impetigo Impetigo is a primary superficial infection of the skin. It is more prevalent in humid climates and occurs most commonly in the summer months. Trauma to the skin, such as a small abrasion or insect bite, sometimes provides the site of entry for the infective bacteria. The lesions evolve from discrete small vesicles into pustules. The fluid content of the primary lesions dries into a thick yellowish crust (Fig. 3-1), and removal of the crust may reveal bright-red and shiny erosions (Fig. 3-2).

The most common cause of impetigo is Staphylococcus aureus. Because the “honey-crusted” lesions of impetigo may be caused by a combination of S aureus and Streptococcus pyogenes, systemic antibiotic therapy should be effective against both organisms. The use of topical mupirocin ointment appears to be an effective treatment and may replace the need for systemic therapy in some patients with localized lesions.

Bullous impetigo This form of impetigo consists of flaccid blisters that quickly rupture and evolve into superficial round or oval erosions with a varnished surface and minimal crust. Blisters are caused by the local effect of staphylococcal toxin. Figure 3-3 shows blisters and superficial erosions.

Figure 3-4 shows the collarettes of scale following rupture of the bullae. Bullous impetigo is associated with a pure culture of S aureus. Oral treatment with dicloxacillin or a cephalosporin is an effective mode of therapy. If methicillin-resistant Staphylococcus aureus (MRSA) is suspected, oral clindamycin is frequently recommended, and can be used pending results of culture.

Impetiginization This is the term for impetigo imposed upon preexisting dermatoses, most commonly insect bites and atopic dermatitis. Eruptions that are pruritic are particularly susceptible to secondary infection. The most common organisms are S pyogenes and S aureus. Figure 3-5 shows a case of impetiginized atopic dermatitis. The development of such “honey-crusted” lesions in a child with eczema suggests the need for systemic antibiotic therapy.

Ecthyma Ecthyma occurs when there is ulceration beneath the surface of a skin infection. If impetigo is infection by streptococci and/or staphylococci superficially in the epidermis, ecthyma is infection by the same organisms through the entire thickness of the epidermis (0.1 mm) to the upper reaches of the dermis (perhaps to a depth of 0.5 mm). Clinically, there is often a firm crust covering a superficial ulcer, surrounded by erythema.

Staphylococcal scalded skin syndrome This eruption occurs most commonly in children under the age of 5 years. It is characterized by a generalized tender, macular erythema, which is most prominent on the skin around the mouth and nose and in intertriginous areas. Within 1 or 2 days, the rash begins to peel. Typically, the large superficial flaccid bullae (“scalded skin”) are quickly unroofed, revealing areas of slightly erythematous and shiny skin. These areas crust and then heal. Children with this syndrome are often extremely irritable and febrile, but the overall prognosis is good. Figures 3-7 and 3-8 illustrate superficial blistering and erythema around the mouth. The scalded skin syndrome is caused by an epidermolytic toxin that may be produced by several strains of S aureus. These causative organisms may be present in the nose, throat, conjunctiva, or an infected wound. Staphylococcal scalded skin syndrome resolves without scarring within a period of 2 weeks. Treatment consists of appropriate supportive care and penicillinase-resistant antibiotics.

Staphylococcal scalded skin syndrome Figure 3-9 shows a generalized light-colored erythema which is accentuated in skin folds. The staphylococcal toxin exfoliatin may sometimes produce extensive areas of desquamation. Other clues to diagnosis include areas of denuded skin in sites of anatomic stress, and skin tenderness.

Treatment in severe cases consists of intravenous antibiotics that are effective against strains of S aureus that are prevalent in the geographic area. Infants with this degree of involvement (Fig. 3-10) must be managed carefully with respect to fluid and electrolyte levels.

Staphylococcal scalded skin syndrome Scalded skin syndrome must be differentiated from scarlet fever, Kawasaki disease, toxic shock syndrome, and drug-induced toxic epidermal necrolysis.

Chancriform pyoderma Infection with a Staphylococcus, or more often with organisms such as Pseudomonas aeruginosa or Proteus and combinations thereof, can result in chancriform ulcers. These lesions are more difficult to treat. In addition to effective systemic antibiotics, attention must be paid to skin care of the entire diaper area, and topical antibiotics may be required.

Folliculitis This is a common form of bacterial skin infection in both children and adolescents. Typically, the lesions are erythematous papules or pustules, arising at the openings of hair follicles. Pruritus or mild discomfort may be associated with the infection.

Involvement of the buttocks and perineum is particularly common in infants and young children (Fig. 3-14). Infants may be predisposed to folliculitis in this area secondary to occlusion by diapers.

Folliculitis, shown in Fig. 3-15 in the beard area, is most commonly caused by infection with S aureus and responds to treatment with oral antibiotics that cover this organism. In areas where methicillin-resistant organisms are common, antibiotic therapy needs to be adjusted accordingly.

Hot tub folliculitis This condition is seen after immersion in a hot tub in which gram-negative organisms, predominantly Pseudomonas species, proliferate as a result of improper maintenance. Patients develop numerous discrete erythematous papules and pustules on the upper trunk, groin, buttocks, and thighs. Lesions may be tender. The eruption is self-limited, although topical gentamicin and/or diluted white vinegar soaks may hasten resolution. Hot tubs must be properly cleaned and maintained.