Impetigo Contagiosa

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Introduction

  • A superficial, highly contagious, bullous skin disorder caused by coagulase positive staphylococci and occasionally -haemolytic streptococci

Clinical features

  • Children are more commonly affected
  • Initial lesions are superficial vesicles, or bullae found around orifices: eyes, nose and ears
  • Begins with a 2 mm erythematous macules which quickly develop into vesicles or bullae
    • Blisters are superficial and rupture easily, releasing a thin straw-coloured seropurulent discharge
    • The exudate dries to form loosely stratified golden yellow crusts
  • Auto-inoculation from fluid (from ruptured blister) leads to multiple lesions
  • As the lesions spread peripherally and the skin clears centrally, large circles are formed by fusion of the spreading lesions to produce gyrate patterns
  • Lesions heal without scarring, but may leave behind erythema and hyperpigmentation
  • Other pruritic dermatoses may become impetiginized (i.e. infected with the above organisms):
    • Scabies
    • Pediculosis
    • Papular urticaria
    • Atopic eczema

Differential diagnoses

  • Ecthyma
  • Herpes simplex

Complications

  • Regional lymphadenopathy
  • Cellulitis
  • Rarely: septicaemia
  • Rarely: acute glomerulonephritis, if nephritogenic strain of streptococcoci is involved

Investigations

  • Wound swab for bacteriology and sensitivity

Treatment goals

  • Treat infection
  • Treat underlying pruritic dermatoses
  • Prevent complications

Non-drug treatment

  • Debride crusted lesions with soap and water or desloughing antibacterial agents
  • Dry weepy lesions with astringent such as potassium permanganate, sodium chloride 0.9% solution, hydrogen peroxide

Drug treatment

Erythromycin

Adult and child over 8 years: 250 - 500 mg orally every 6 hours

or 

500 mg - 1 g every 12 hours for 5 - 10 days

Child: up to 2 years: 125 mg orally every 6 hours;

         2 - 8 years: 250 mg every 6 hours

Or:

Co-trimoxazole

Adult: 960 mg orally every 12 hours for 5 - 10 days

Child: 6 weeks - 5 months: 120 mg;

6 months - 5 years: 240 mg;

6 - 12 years: 480 mg taken orally every 12 hours for 5 - 10 days

Supportive measures

  • Debride crusted lesions: Dislodging antibacterial agen. Avoid auto-inoculation e.g. with fingers, shaving brushes, handkerchiefs, or pillow cases
  • Strict personal hygiene
  • Treat underlying skin disease(s)

Notable adverse drug reactions, contraindications and caution

  • Sulphonamide and co-trimoxazole: fixed drug eruption