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Toronto Notes 2019
Infections
Dermatology D25
Infections
Stratum corneum
Impetigo
(Stratum corneum, epidermis)
Erysipelas
(Upper dermis & lymphatics only)
Rarely involves lower dermis; subepidermal oedema underlying an uninvolved epidermis
Cellulitis
(Lower dermis & subcutaneous fat)
Primarily not raised and demarcation less distinct than erysipelas
Necrotizing fasciitis
(Subcutaneous fat, fascial planes, and deep muscle)
Location Matters!
e.g. Group A Strep Infections
• Impetigogjust below stratum corneum
• Erysipelasgepidermis and upper dermis
only
• Cellulitisgprimarily lower dermis
and subcutis (primarily not raised, and
demarcation less distinct than erysipelas)
• Necrotizing fasciitisgdeep fascia and
muscle
Upper dermis Lower dermis
Subcutaneous fat
Deep fascia Muscle
©Ashley Hui 2016
Figure 7. Layers of skin affected by bacterial infections
Bacterial Infections
EPIDERMIS
IMPETIGO
Clinical Presentation
• acutepurulentinfectionwhichappearsvesicular;progressestogoldenyellow“honey-crusted”lesions surrounded by erythema
• canpresentwithbullae
• commonsites:face,arms,legs,andbuttocks
Etiology
• GAS,S.aureus,orboth Epidemiology
• preschoolandyoungadultslivingincrowdedconditions,poorhygiene,neglectedminortrauma
Differential Diagnosis
• infectedeczema,HSV,VZV
Investigations
• Gramstainandcultureoflesionfluidorbiopsy
Management
• removecrusts,usesalinecompresses,andtopicalantisepticsoaksbid
• topicalantibacterials(e.g.2%mupirocinorfusidicacid(Canadaonly)tid;continuefor7-10dafter
resolution)
• systemicantibiotics(e.g.cloxacillinorcephalexinfor7-10d)
Hypodermis Dermis Epidermis