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Impetigo (Pathophysiology (Types Non-bullous (commonest): no bacterial…
Impetigo
Pathophysiology
Types
Non-bullous (commonest): no bacterial toxins produced
Bullous (fluid filled lesions >5mm diameter): toxins from S aureus cause loss of cell adhesion in superficial epidermis
Agent
S aureus, S pyogenes, or both
MRSA
also (increasingly common)
Mechanism
Bacteria enter skin through breaks from minor trauma or underlying skin condition e.g. eczema, scabies, chickenpox
Incubation 4-10d
Transmission
Close skin-skin contact or sharing contaminated objects
(e.g. clothes, towels)
Risk
factors
Pre-existing skin disease
Hot/humid weather
Poor hygeine
Crowding
Differentials
Autoimmune/inflammatory
Atopic/contact dermatitis
Pemphigus vulgaris
Bullous pemphigoid
Lupus
Erythema multiforme
Infection
Bacterial: cellulitis, erysepelas, staph scalded skin syndrome, necrotising fasciitis
Fungal skin infection: candida, tinea
Parasitic: scabies
Viral: VZV, HSV
Trauma
Insect bites
Burns/scalds
Drugs
Drug reactions
Diagnosis
Examination
Derm examination
Well defined erythematous patches, papules, pustules, blisters, characteristic honey crust, any regional LNs
Investigations
Bedside
Obs (may have fever)
Swabs
Indication: persistent/recurrent disease
Swab lesion (moist lesion/deroofed blister) for MCS
Swab nose (if recurrent to determine nasal staph carriage)
History
DH
Current meds, recent abx, allergies
FH
Affected contacts
PMH
Skin conditions, other medical conditions,
immunosuppression
SH
Living arrangements,
occupation/school/nursery
PC/HPC
Rash: site, onset, character (red, blistering, crusty, itch, pain)
Associated symptoms: fever, LNs, malaise
Anyone else affected, trauma to skin, recent travel
Prognosis
Usually self limiting, 2-3w if untx
Relapses common if
únderlying skin condition
Can be lifethreatening in neonates
or immunosuppressed patients
Epidemiology
Common
Children 2-5y
Clinical
presentation
Non-bullous
Rash
Vesicles/pustules, erythema, honey crust
May have flaccid blisters
Often nose and face, can be anywhere
Heals 2-3w no scarring
Systemic signs
Rare; fever, lymphadenopathy
Bullous
Rash
Flaccid, fluid filled vesicles and blisters
Rupture leaving thin flat crust
Heals 2-3w no scarring
Systemic features
If large areas involved; fever, LN, D+V
Management
Conservative
Information, advice, support
Refer/admit if complications, neonate or immunosuppressed;
unclear diagnosis, lesions recurrent/not responsive to tx
Self care (wash areas soap/water, hang hygeine, avoid scratching, avoid sharing clothes/towels, absence from school/nursery until scabbed over/48h after starting abx)
Medical
Topical abx
Indication: mild infection
E.g. fusidic acid TDS 5d
Oral abx
Indication: severe/widespread, acute unwell
E.f. PO flucloxacillin 7d (clarithromycin if allergic)
Complications
Spreading infection
Cellulitis
Lymphangitis
Osteomyelitis
Septic arthritis
Sepsis
Inflammation
Strep: acute GN, scarlet fever, urticaria, erythema multiforme
Staph: staphlococcal scalded skin syndrome
Definition
Superficial bacterial
infection of the skin
