Observing the skin's physical appearance, or swabbing a culture of the lesion for S. aureus. Nasal swabs from the patient's immediate family members are necessary to identify them as being asymptomatic nasal carriers of S. aureus. Histology The epidermis is composed of four layers, stratum basale, stratum spinosum, stratum granulosum, and stratum corneum. The cleavage plane can be found either subcorneally or within the upper stratum granulosum. The roof of the pustule is parakeratotic stratum corneum, and the floor is formed of keratinocytes, which may or may not be acantholytic. Neutrophils begin to fill the pustule. Toxins are produced by S. aureus and target desmoglein, which is a desmosomal cell-cell adhesion molecule found in the upper levels of the epidermis. This correlates with the subcorneal localization of the bullae. Uncommon variants * Erythema multiforme * Systemic lupus erythematosus * Stevens–Johnson syndrome * Pemphigus vulgaris Differential * HPV * Insect bites * Burns * Herpes simplex 1/2
Bullous impetigo
Impetigo herpetiformis
Impetigo
Bovine papular stomatitis
Streptococcal intertrigo
Paederus dermatitis
Granulomatous facial dermatitis
Contact stomatitis