Makindo Medical Notes

Related Subjects: |Cellulitis |Impetigo |Pyoderma gangrenosum |Pemphigus Vulgaris |Toxic Epidermal Necrolysis |Stevens-Johnson Syndrome |Necrotising fasciitis |Gas Gangrene (Clostridium perfringens) |Anatomy of Skin |Skin Pathology and lesions |Skin and soft tissue and bone infections

About

• Impetigo is a highly contagious superficial bacterial skin infection.
• It involves the epidermis and is most common in school-aged children 👧🧒.
• Risk factors: hot weather ☀️, poor hygiene 🧼, skin trauma, and crowded living conditions.

Aetiology

• Staphylococcus aureus (most common cause).
• Streptococcus pyogenes (Group A strep, sometimes co-infection).
• Occasionally due to MRSA in resistant or recurrent cases.

Clinical Features

• “Honey-coloured” golden crusts 🍯 on erythematous skin.
• Blisters and erosions → drying → crusted lesions.
• Common sites: face (esp. perioral/perinasal), arms, legs.
• Non-bullous impetigo: small pustules that rupture → golden crust.
• Bullous impetigo: flaccid bullae that spread quickly, more common in neonates/infants.

Differential Diagnoses

• Herpes simplex (grouped vesicles, recurrent).
• Varicella (chickenpox, crops of vesicles at different stages).
• Contact dermatitis (itchy, non-infective).
• Insect bites with secondary infection.

Investigations

• Usually clinical diagnosis.
• Swabs: bacterial culture for recurrent/atypical/severe cases, or if MRSA suspected.
• Gram stain/PCR occasionally in outbreaks or unclear diagnosis.

Management

Mild = topical antibiotics. Moderate/severe = systemic antibiotics. Always advise on hygiene & isolation until lesions crusted/healed.

• Topical mupirocin or fusidic acid for localized mild infection.
• Systemic flucloxacillin (first line) or clarithromycin if penicillin-allergic.
• Cephalexin or clindamycin may be used in resistant strains.
• MRSA → use sensitivities (e.g., doxycycline, trimethoprim-sulfamethoxazole).
• Supportive: antibacterial washes, avoid scratching, keep nails short.
• Isolation: exclude from school/nursery until 48h after starting antibiotics or until lesions crusted/healed.

References

• NICE – Impetigo (NG153)
• CDC – Impetigo
• DermNet NZ – Impetigo

Revisions

• Added case vignettes to illustrate presentations and complications.
• Updated management to reflect NICE recommendations (2020+).

3 Clinical Cases — Impetigo 🦠🩹

• Case 1 — Non-bullous impetigo in a child 👧: A 6-year-old girl presents with multiple itchy sores around her mouth and nose. Lesions start as red macules, quickly evolving into honey-coloured crusts. She is otherwise well. Teaching: This is the commonest form of impetigo, usually due to Staphylococcus aureus or Streptococcus pyogenes. Treatment: topical fusidic acid or hydrogen peroxide; oral antibiotics if widespread.
• Case 2 — Bullous impetigo in an infant 👶: A 10-month-old baby develops flaccid blisters on the trunk that rupture to leave shallow erosions with a varnish-like crust. He is mildly febrile but feeding well. Teaching: Bullous impetigo is caused by toxin-producing S. aureus which disrupts desmoglein-1. It tends to affect infants. Management: oral flucloxacillin; infection control advice to carers.
• Case 3 — Recurrent impetigo in an adult healthcare worker 🧑‍⚕️: A 34-year-old nurse has recurrent impetigo on her forearms despite multiple antibiotic courses. Screening shows nasal carriage of S. aureus. Teaching: Recurrent impetigo is often linked to staphylococcal carriage. Management includes eradication therapy (nasal mupirocin, chlorhexidine washes) alongside standard treatment. Occupational hygiene advice is crucial.