Impetigo is a superficial skin infection seen frequently in children.
It is one of the most common skin and soft tissue infections observed in pediatrics.
Pyoderma and impetigo contagiosa are synonyms for impetigo.
Classification
Primary impetigo: direct bacterial invasion of previously normal skin
Secondary impetigo: infection at sites of minor skin trauma or underlying conditions
Types of impetigo
Nonbullous impetigo
Most common form
Lesions begin as papules that progress to vesicles surrounded by erythema.
Subsequently, the papules mature into pustules that enlarge and break down to form thick, adherent, golden crusts.
Bullous impetigo
Vesicles enlarge to form bullae containing clear yellow fluid, which become darker and more turbid.
Ruptured bullae leave a honey-colored crust.
Ecthyma
An ulcerative form of impetigo
Lesions extend through the epidermis and deep into the dermis.
Epidemiology
Location: most frequently in tropical or subtropical regions but also prevalent in northern climates during summer months
Age: found most commonly in children aged 2-5 years and can spread rapidly through child care centers and schools
Risk Factors
Poverty, overcrowding
Poor hygiene
Underlying scabies infection
Eczema
Etiology
Staphylococcus aureus: most common etiologic agent. Toxin-producing strains cause cleavage in superficial skin layer.
Impetigo due to community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has occurred in a minority of cases.
Beta-hemolytic streptococci (primarily group A, but serogroups C and G have been implicated in some cases)
Diagnosis
History
Patients with impetigo may report a history of minor trauma, insect bites, scabies, herpes simplex virus infection, varicella infection, or eczema before the development of the infection. Lesions are usually present for a few days to weeks before the patient seeks medical attention.
Lesions may be described as itchy but are usually painless.
Additional symptoms such as fever, respiratory distress, vomiting, or diarrhea are rare and perhaps indicative of another diagnosis.
Outbreaks commonly occur in families and child care centers as well as among sports team members.
Physical Exam
Nonbullous impetigo
Usually occurs on exposed areas of body, most frequently the face and extremities
Lesions first begin as papules or thin-walled vesicles on an erythematous base. The lesions gradually enlarge, may coalesce, and break down over the course of 4-6 days. After rupture, their serum is released, which dries and forms a thick brown, "honey-colored"¯ crust.
As the lesions resolve with treatment, the crusts slough from the affected areas and may leave hypopigmented areas.
Lymphadenopathy is rare.
Bullous impetigo
Lesions may form on grossly normal or previously traumatized skin.
Appear initially as superficial vesicles that rapidly enlarge to form flaccid bullae, filled with clear yellow liquid that gradually becomes more turbid and sometimes purulent.
After the lesions rupture, a thin, light brown crust remains.
Lymphadenopathy is rare.
Ecthyma
The lesion is a vesicle or pustule overlying an inflamed area of skin that deepens into a dermal ulceration. "Punched-out"¯ ulcers are covered with yellow crust, surrounded by raised violaceous margins.
Ecthyma heals slowly and commonly produces a scar.
Regional lymphadenopathy may occur, but systemic symptoms are usually absent.
Lab
Impetigo is a clinical diagnosis, and no laboratory workup is routinely indicated.
Culture of bullae or purulent fluid may be useful in patients who have failed empiric treatment. Swabs of intact skin are not helpful.
If MRSA is suspected, a Gram stain and culture of lesion should be considered.
If systemic symptoms are present, a CBC and blood culture should be considered to evaluate for other possible causes of infection.
Skin biopsy may be useful if diagnosis is unclear.
Differential Diagnosis
Varicella
Staphylococcal scalded-skin syndrome
Erythema multiforme
Herpes simplex virus infection
Burns (thermal and chemical)
Contact dermatitis
Atopic dermatitis
Tinea corporis
Insect bites
Scabies
Lice
Treatment
Medication
Topical therapy
Topical therapy is preferred when there are a limited number of lesions without bullae.
Mupirocin
2% ointment or cream
Children >2 months old
Applied to affected areas three times daily for 5 days
Retapamulin
1% ointment
Children >9 months old
Applied to affected area (up to 2% body surface area[BSA]) twice daily for 5 days
Although the components of over-the-counter triple antibiotic ointments (bacitracin, neomycin, polymyxin B) have some activity against the organisms causing impetigo, they are not considered effective for treatment.
Oral therapy
Oral antibiotic therapy should be used for impetigo when the lesions are bullous or when topical therapy is impractical due to the extent or location of lesions.
Methicillin-sensitive Staphylococcus aureus (MSSA) or beta-hemolytic streptococci
Amoxicillin/clavulanic acid 40 mg/kg/24 h PO in 2 divided doses
Cephalexin 25 mg/kg/24 h PO in 4 divided doses
Dicloxacillin 12.5 mg/kg/24 h PO in 4 divided doses
Clindamycin 15-25 mg/kg/24 h PO in 3 divided doses
Erythromycin 40 mg/kg/24 h PO in 4 divided doses
When MRSA is suspected
Clindamycin 15-25 mg/kg/24 h PO in 3 divided doses
Trimethoprim-sulfamethoxazole: trimethoprim 8 mg/kg and sulfamethoxazole 40 mg/kg daily PO in 2 divided doses (has activity against MRSA but not against streptococci)
Additional Treatment
General Measures
Clipping fingernails short to minimize effects of scratching is recommended.
Hand washing is important for reducing spread among children, as is covering the lesions.
Treatment is important for reducing spread of infection to self and others.
Cleansing and debriding the lesions are unnecessary.
Crusted lesions can be cleansed gently with soap and water.
Ongoing Care
Follow-up Recommendations
Duration of therapy
The duration of antimicrobial therapy should be tailored to clinical improvement; 7 days of treatment is usually adequate.
Children should be excluded from out-of-home child care until 24 hours after treatment has been initiated.
Signs of incomplete therapy
Recurrent infection may indicate incomplete therapy, reinfection, or an S. aureus carrier state.
Development of fever is unusual and may indicate a more serious infection and/or the presence of cellulitis or an abscess.
Prevention of recurrence
Impetigo frequently spreads among close contacts and family members.
Patients and family members should wash their hands frequently.
Keep clothes and bedding clean.
Do not share towels and other personal care items.
Underlying skin conditions (e.g., eczema) and infestations (e.g., scabies) should be treated appropriately to decrease the likelihood of the development of impetigo.
Complications
Cellulitis
Lymphangitis
Suppurative lymphadenitis
Staphylococcal scalded-skin syndrome
Poststreptococcal glomerulonephritis
Most cases are believed to be caused by a preceding streptococcal impetigo rather than streptococcal pharyngitis.
Deposition of group A beta-hemolytic streptococci (GABHS) nephrogenic antigens induce immune complex formation in kidneys.
Latent period is 3-6 weeks following skin infection.
Scarlet fever, osteomyelitis, septic arthritis, pneumonia, septicemia, and rheumatic fever have also been observed in patients with impetigo.
Prognosis
The lesions of impetigo usually heal without significant scarring. Overall, the infection is highly curable, but the condition often recurs in young children.
Additional Reading
Koning S, van der Sande R, Verhagen AP, et al. Interventions for impetigo. Cochrane Database Syst Rev. 2012;1:CD003261. [View Abstract]
Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft-tissue infections. Clin Infect Dis. 2005;41(10):1373-1406. [View Abstract]
359751003 Impetigo due to Staphylococcus aureus (disorder)
399183005 Impetigo bullosa (disorder)
FAQ
Q: Which is the more effective treatment for impetigo-oral or topical antibiotics?
A: In general, if there are a few localized lesions, topical therapy is preferred. If there is more diffuse involvement, or systemic symptoms, a course of oral antibiotics is recommended.
Q: Can a child with impetigo attend school or child care?
A: The child should be excluded from child care until 24 hours after treatment has been initiated. Once the lesions begin to improve, the child may resume his or her activities without restrictions.
Q: How does one help prevent impetigo from spreading?
A: Gently wash the affected areas with mild soap and running water, use the antibiotics (topical or oral) as directed, and then cover lesions with bandages. Wear gloves when applying any antibiotic ointment to the patient's lesions and endorse thorough hand washing afterward. Do not share clothes, linens, or towels used by the affected individual until the infection has cleared.