Skin-nontumor / Clinical dermatology
Blistering disorders
Bullous impetigo

Author: Mowafak Hamodat, M.D., MB.CH.B, MSc., FRCPC (see Authors page)

Revised: 10 June 2016, last major update July 2011

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Bullous impetigo

Cite this page: Bullous impetigo. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/skinnontumorbullousimpetigo.html. Accessed December 10th, 2016.
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:

Various images



Abdomen

Micro 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
Micro 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’s 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