Skin nontumor
Vesiculobullous and acantholytic reaction patterns
Bullous impetigo
Last author update: 1 July 2011
Last staff update: 11 November 2020
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PubMed Search: Bullous impetigo
Table of Contents
Definition / general | Etiology | Clinical features | Treatment | Clinical images | Microscopic (histologic) description | Microscopic (histologic) images | Differential diagnosisCite this page: Hamodat M. Bullous impetigo. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skinnontumorbullousimpetigo.html. Accessed March 27th, 2023.
Definition / general
- Impetigo is due to bacterial infection of superficial epidermis, most common in infants and children
- Either primary infection due to bacterial invasion through minor breaks in skin, or secondary infection of preexisting dermatosis or infestation
- Bullous form of impetigo has confluent pustules with honey-colored crusts, usually on face, trunk, buttock, perineum or extremities; nonbullous form also exists
- See also impetigo
Etiology
- Due to impetigo (Staphylococcus aureus infection) and its exfoliative toxins A and B, which target desmoglein 1, a desmosomal adhesion molecule in upper epidermis (J Dermatol Sci 2008;49:21)
- Community acquired methicillin-resistant S. aureus is common (Cutis 2010;85:65)
- In non-Western countries, Streptococcus pyogenes is an important cause (PLoS Negl Trop Dis 2009;3:e467)
- Highly contagious, may be spread by asymptomatic healthcare workers (J Hosp Infect 2007;67:264)
- Simple impetigo may occur in endemic or epidemic form and spread to involve siblings and schoolmates
Clinical features
- Confluent pustules with honey-colored crusts, usually on face, trunk, buttock, perineum or extremities
- Vesicles rapidly enlarge and become flaccid transparent bullae up to 5 cm, containing clear yellow to dark yellow / turbid fluid
- Margins are sharply demarcated without erythema
- Negative Nikolsky sign (sheet-like removal of epidermis with sliding pressure)
- Highly contagious; may occur in outbreaks (Antonie Van Leeuwenhoek 2009;95:387, Euro Surveill 2009;14:19372)
- May affect caregivers (Cutis 2008;81:115)
- Usually indicates penicillin resistance
- Risk factors include skin abrasions, trauma, burns, poor hygiene, insect bites, diabetes mellitus, primary varicella infection, eczema, atopic dermatitis; also carriers of Staphylococcal aureus in nose or perineum (Can Fam Physician 2008;54:193)
- Diagnosis is usually clinical; can also culture blister fluid; obtain blood cultures if systemic; biopsies are uncommon
- May overlap with blistering distal dactylitis - acral oval bullae 10 - 30 mm in diameter (Clin Exp Dermatol 2007;32:314)
Treatment
- Local treatment with 2% mupirocin ointment or fusidic acid plus local care (cleansing, removal of crusts, application of wet dressings - Am Fam Physician 2007;75:859, eMedicine #1, #2)
- Up to 50% of strains of S. aureus may be resistant to fusidic acid (Acta Derm Venereol 2010;90:52, Clin Exp Dermatol 2009;34:136)
- Disease is usually self-limited, but treatment relieves discomfort, improves cosmetic appearance, prevents spread of organism that also causes glomerulonephritis and other illnesses
- Complicated or diffuse disease (staphylococcal scalded skin syndrome) requires 5 - 10 days of beta-lactamase resistant antibiotics (cephalexin, amoxicillin and clavulanate); erythromycin may be effective in communities with low levels of penicillin resistance
- Complications include lymphadenitis, cellulitis, glomerulonephritis and sepsis
Clinical images
Images hosted on other servers:
Bullous impetigo in shoulder region
Abdomen
Microscopic (histologic) description
- Cleavage plane is subcorneal or upper granular layer
- Variable acantholysis
- Pustule is filled with neutrophils, and bacterial clusters are evident with Gram stain
- The underlying dermal infiltrate contains a mixed neutrophil and lymphocytes infiltrate; neutrophils may be seen in the spongiotic stratum spinosum
Microscopic (histologic) images
Images hosted on other servers:
Subcorneal blister with inflammatory cells
Differential diagnosis
- Allergic contact dermatitis: different clinical history, extensive spongiosis, numerous eosinophils
- Antibodies in a pemphigus like pattern: may be demonstrated in bullous impetigo and distinction from pemphigus foliaceous may therefore be a problem; generally the presence of numerous neutrophils and the recognition of Gram positive cocci is sufficiently characteristic of impetigo, as acantholytic cells are very scanty
- Herpes simplex infection: different clinical history, viral inclusions
- Insect bites: different clinical history
- Other blistering disorders: including chronic bullous dermatosis of childhood (J Telemed Telecare 2009;15:208)
- Subcorneal pustular dermatosis and pustular psoriasis
- Superficial variant of pemphigus: particularly as the latter become secondarily infected and there may be one or two acantholytic cells in impetigo
- Thermal burns: different clinical history
