Definition
Erysipelas is an acute bacterial infection of the upper dermis and superficial lymphatics, producing a well-demarcated, raised area of inflammation.
Causative Organisms
- Streptococcus pyogenes (Group A strep) β most common.
- Less commonly: Group B, C, G streptococci.
π‘ Distinction:
- Erysipelas β almost always streptococcal.
- Cellulitis β can be strep or staph.
Risk Factors
- Breaks in skin barrier (trauma, eczema, tinea pedis, ulcers).
- Chronic oedema, lymphatic obstruction.
- Diabetes, obesity.
- Immunosuppression.
Clinical Features
- Abrupt onset with fever, chills, malaise.
- Bright red, swollen, warm plaque with raised and sharply demarcated borders.
- Commonly affects face and lower limbs.
- May see lymphangitic streaking and tender regional lymph nodes.
β οΈ Severe cases β blistering, bullae, systemic toxicity.
Differentials
- Cellulitis β deeper infection, poorly defined margins, less raised.
- Contact dermatitis β pruritic, usually bilateral, not febrile.
- Venous eczema β chronic, itchy, less acute.
- Necrotising fasciitis β severe pain, systemic shock, rapidly spreading.
Investigations
- Usually clinical diagnosis.
- Swabs/cultures only if open wounds or recurrent infection.
- Blood cultures in systemic illness.
Management
General
- Rest, elevation of limb.
- Analgesia.
Antibiotics (oral unless severe)
- Phenoxymethylpenicillin (penicillin V) β first choice for mild/moderate disease.
- Flucloxacillin β alternative, especially if cellulitis overlap suspected.
- Clarithromycin or doxycycline β if penicillin-allergic.
Severe/systemic infection
- IV benzylpenicillin or flucloxacillin.
π‘ Facial erysipelas often requires inpatient care because of risk of complications (e.g., cavernous sinus thrombosis).
Complications
- Abscess formation.
- Recurrent erysipelas β chronic lymphoedema.
- Rare: sepsis, meningitis (if facial/cranial involvement).
Quick Clinical Pearls
- Raised, well-demarcated edge β erysipelas.
- Poorly defined, deeper infection β cellulitis.
- Facial erysipelas = hospital referral.
- Always check for predisposing skin conditions (athleteβs foot, ulcers).
Example Clinical Scenario
Case:
A 60-year-old woman presents with fever and a rapidly developing painful red area on her right cheek. Examination shows a bright red, swollen plaque with raised, sharply demarcated edges.
Most likely diagnosis? β Erysipelas
Best initial antibiotic (oral, no allergy, stable)? β Phenoxymethylpenicillin
π Next logical topic would be Necrotising Fasciitis, since together with cellulitis and erysipelas it forms a classic differential set.
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