Impetigo: Clinic, diagnosis and treatment

• Impetigo is a common bacterial skin condition, mainly caused by Group A Streptococcus (more rarely B, C and G) and/or Staphylococcus aureus.
• It manifests itself as erythematous, vesicular and then pustular and crusty skin lesions. These lesions are sometimes painful and can develop on any part of the body, but they are found mostly on the face, especially the periorificial areas, hands and arms. Impetigo lesions may be small and isolated, or larger and numerous. They may also coalesce into plaques. The perilesional skin may be inflammatory^1,2.
• Impetigo is highly contagious, most often transmitted by direct contact with the lesions of an infected person or by indirect contact with contaminated objects such as towels, clothing or toys. It can also spread by self-infection. In children, small outbreaks within the family or the community are common.
• The treatment of impetigo is based on topical antibiotic therapy and often oral in case of disseminated lesions.  Prompt treatment and good hygiene are necessary to prevent the transmission of impetigo by being absent from school for a few days, washing hands frequently, keeping fingernails short and avoiding sharing personal belongings (towels, linen...). People with impetigo should avoid touching their lesions, wearing a bandage on exposed areas during the day can be useful though it does promote maceration.
• Where possible, siblings should be examined and treated for lesions^1,2.
• Because of the risk of post-streptococcal glomerulonephritis, the normality of the urinary tract should be checked at D15. This risk should not be trivialized, and treatment should not be limited to antiseptics, which are not sufficient to effectively control the symptoms^1,2.

• Impetigo is related to superficial invasion of the skin by Group A Streptococcus and/or Staphylococcus aureus.
• These bacteria are normally present on the skin and mucous membranes, but they can cause infections when they enter damaged skin or when the normal skin microbiota is disturbed^1,2.
• Some strains may be secretors of pathogenic toxins.

Clinical presentations of impetigo may vary depending on the underlying cause, location of the lesion, and severity of the infection. The most commonly observed symptoms include^1,2:

• Erythematous, vesicular, then pustular and crusty skin lesions, sometimes painful or pruritic.
• Bullous lesions are possible (staphylococcal impetigo).
• Location: ubiquitous but face, periorificial areas and extremities are more frequently affected. 
• The presence of general signs, such as fever and adenopathy, is rare.

Non-bullous impetigo

• It is the most frequent form of impetigo.
• It mainly concerns young children aged between 2 and 6 years old: subcorneal vesiculobullous lesions with clear content, secondarily purulent.
• The rupture of the vesiculobullous roof exposes an erosive, inflammatory, crusty aspect, with a circinate arrangement (perioral damage with presence of honey-colored crusts adopting a round or circinate configuration).
• Pruritus leads to self-inoculations at a distance from the primary site of infection (trunk, limbs)^1,2.

Bullous impetigo

• It is characterized by fluid-filled blisters on the skin, usually infected with staphylococcus aureus.
• Bullous impetigo results in large bullae (1 to 2 cm in diameter) affecting the buttocks or face, sometimes the palms, the soles and the oral mucosa.
• It often affects infants or small children.
• The clear content-filled blisters become disrupted and ulcerate to form ulcerating and crusty lesions surrounded by an inflammatory halo^1,2.