Diagnosis

Impetigo

Etiology

Cause [1pg]

• Staphylococcus aureus: 80% of cases

• Group A beta hemolytic streptococci (Streptococcus pyogenes): 10% of cases

Pathophysiology [1pg]

1. Primary impetigo: Previously normal skin affected by direct bacterial invasion.

2. Secondary impetigo: Infection forming at a disrupted skin (wound site):

   • Bites, cuts, abrasions, trauma, or diseases (herpes simplex, varicella, eczema)

3. Bullous impetigo is a toxin-mediated erythroderma (exotoxin targets desmoglein), resulting in bullae and large areas of skin loss.

Risk factors [a8q][1pg]

• Humid weather

• Overcrowding

• Poor hygiene

• Pre-existing skin conditions (e.g. eczema)

• Malnutrition

• Immunosuppression

• Diabetes

Complications [hyq][1pg]

• Poststreptococcal glomerulonephritis

• Scarlet fever

• Staphylococcal scalded skin syndrome (SSSS)

• Osteomyelitis

• Septic arthritis

• Sepsis

• Guttate psoriasis

• Cellulitis

• Erysipelas

• Erythema multiforme

• Urticaria

• Ecthyma

Epidemiology

Incidence per 100.000 [nsd]

Approach

• Blood test

• Gram stain

• Culture

• Biopsy

Treatment

Usually self-resolves within two to three weeks [hyq][1pg]

1. Gentle cleansing: antibacterial soap (chlorhexidine)

2. Topical antibiotics: fusidic acid, hydrogen peroxide 1%

3. Systemic antibiotics: cephalosporins, amoxicillin-clavulanate, dicloxacillin, clindamycin, doxycycline

Differential diagnoses

Acute febrile neutrophilic dermatosis, Bullous pemphigoid, Burn wound, Candidiasis, Dermatitis herpetiformis, Drug eruptions, Eczema, Erysipelas, Folliculitis, Herpes simplex, Herpes zoster, Insect Bite, Pediculosis, Pemphigus vulgaris, Scabies, Staphylococcal scalded skin syndrome, Sweet syndrome, Systemic lupus erythematosus, Tinea, Varicella