Erysipelas
Superficial cellulitis with prominent lymphatic involvement, sharply demarcated borders, and a classic 'peau d'orange' appearance — almost always streptococcal.
Also known as: erysipelas, St. Anthony's fire
Overview
Acute bacterial infection of the upper dermis and superficial lymphatics, characterized by a brilliantly erythematous, raised, sharply demarcated plaque. Caused predominantly by beta-hemolytic streptococci, especially group A (Streptococcus pyogenes); rarely groups C and G or Staphylococcus aureus.
Epidemiology
Bimodal: young children and elderly adults. More common in females. Recurrence in 10-30%, especially with persistent lymphedema.
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Risk factors
- Lymphatic obstruction (post-mastectomy, filariasis, prior cellulitis)
- Venous insufficiency, chronic leg edema
- Skin barrier breakdown (tinea pedis is the leading entry point for lower-leg erysipelas)
- Obesity, diabetes
- Nephrotic syndrome (children)
Pathophysiology
Streptococci enter through minor breaks in skin and spread through the superficial dermal lymphatics, producing the characteristic raised border. Bacterial proteins (M protein, hyaluronidase, streptolysins) drive rapid lymphatic spread and brisk inflammatory response.
Clinical presentation
Symptoms
- Abrupt onset of fever, chills, malaise — often precedes rash by hours
- Localized burning pain and tenderness
- Bright red, hot, swollen plaque with sharply raised border
Signs / physical exam
- Classic distribution: lower extremities (most common) or face (cheeks in 'butterfly' pattern crossing nasal bridge)
- Sharply demarcated, raised, brilliant erythematous plaque ('peau d'orange' surface from edema around hair follicles)
- Regional lymphadenopathy and lymphangitic streaking
- Possible bullae in severe disease
Classic findings
A sharply demarcated, raised, fiery red facial or leg plaque with a clear edge ('the lesion you can trace') and a high fever — classic erysipelas.
Differential diagnosis
- Cellulitis — Deeper, less sharply demarcated, often less brightly red; pathogens and treatment overlap but presentation differs
- Contact dermatitis — Pruritus dominant, vesicles, geometric pattern matching exposure; no fever
- Herpes zoster — Dermatomal distribution, grouped vesicles, prodromal neuropathic pain
- Necrotizing fasciitis — Pain out of proportion, rapid expansion, bullae, crepitus, toxicity — surgical emergency
- Erysipeloid (Erysipelothrix rhusiopathiae) — Occupational (fish, meat handlers), violaceous hand lesion without systemic toxicity; penicillin first-line
- DRESS / fixed drug eruption — Recent drug exposure, eosinophilia, mucosal involvement
Diagnostic workup
Diagnostic criteria
Clinical: sharply demarcated, raised, brightly erythematous, warm, tender plaque with systemic symptoms.
Labs
- Clinical diagnosis — labs not routinely required
- CBC, CRP, ESR if hospitalized or severe
- Blood cultures yield in ~5% — only if systemic toxicity, immunocompromise, atypical presentation
- ASO/anti-DNase B may support recent streptococcal infection but not used acutely
Imaging
- Not required for typical presentations
- Ultrasound to exclude abscess if purulence suspected
Diagnostic algorithm
| Feature | Erysipelas | Cellulitis |
|---|---|---|
| Depth | Upper dermis, lymphatics | Deeper dermis, subcutaneous fat |
| Border | Sharply demarcated, raised | Diffuse, indistinct |
| Color | Brilliant red, peau d'orange | Pink-red, less intense |
| Onset | Abrupt, fever precedes rash | Gradual |
| Pathogen | Group A strep (predominant) | Strep or Staph (incl. MRSA) |
| First-line therapy | Penicillin, amoxicillin | Cephalexin ± MRSA coverage |
Treatment
First-line
- Penicillin remains drug of choice — narrow spectrum, predictable streptococcal coverage:
- • Oral: penicillin VK 500 mg PO QID or amoxicillin 500 mg PO TID × 5-10 days
- • IV: penicillin G 1-2 million units IV q6h, or ceftriaxone 1 g IV daily
- Cephalosporins or macrolides for penicillin-allergic patients (clindamycin or azithromycin)
- Beta-lactam for skin — cefazolin, cephalexin, dicloxacillin acceptable
- Elevation of affected extremity speeds resolution
- Treat underlying tinea pedis to reduce recurrence
Second-line / adjunct
- Add MRSA coverage (vancomycin, linezolid, daptomycin) only if atypical features, purulence, or treatment failure
- Recurrent disease (≥3 episodes/year): low-dose penicillin V 250 mg PO BID prophylaxis (PATCH trial)
Complications
- Recurrent erysipelas with progressive lymphedema
- Streptococcal bacteremia and sepsis
- Post-streptococcal glomerulonephritis (rare)
- Cavernous sinus thrombosis (facial erysipelas in the danger triangle)
- Necrotizing fasciitis if invasive group A strep evolves
PANCE pearls
- Facial erysipelas often crosses the nasal bridge in a butterfly pattern — distinguishes it from herpes zoster, which respects the midline.
- Lower-leg erysipelas in an adult is overwhelmingly streptococcal; MRSA coverage usually unnecessary in non-purulent disease.
- Treat tinea pedis (interdigital cracking) — the most common entry portal for recurrent lower-extremity erysipelas.
- Sharply raised, well-demarcated borders distinguish erysipelas from cellulitis on physical exam.
- Penicillin prophylaxis reduces recurrence by ~half in patients with frequent episodes (PATCH I).
References
- IDSA 2014 — Stevens et al., Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections (Clin Infect Dis)
- PATCH I — Thomas et al., Penicillin to prevent recurrent leg cellulitis/erysipelas (NEJM 2013)
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