Erysipelas

Acute bacterial infection of the upper dermis with prominent lymphatic involvement, almost always caused by beta haemolytic streptococci (group A most often, also C and G). Occasionally S. aureus is involved.

• Characteristically involves the face (in infants, young children and the elderly) and the lower limbs (most adults). Ear involvement is typical.
• Predisposing factors: lymphoedema, venous insufficiency, obesity, tinea pedis, skin fissures, ulcers, nasal or oropharyngeal infection (facial disease), previous erysipelas, diabetes and surgical wounds.
• Recurrence occurs in 10 to 30% of patients within 3 years, and each episode further damages lymphatics.
• It differs from cellulitis by its superficial level: the edge is sharply demarcated and raised, whereas cellulitis spreads deeper with a diffuse margin. The two overlap clinically.

• Abrupt onset, often with fever above 38 C, chills, malaise and headache that precede the skin changes by 4 to 48 hours.
• A bright red, shiny, firm, oedematous, warm plaque with a sharply demarcated, palpably raised border. The skin is tender, with peau d'orange change. There may be vesicles or bullae and, rarely, petechiae.
• Facial disease classically forms a butterfly distribution across the cheeks and nose, and involvement of the ear helix is characteristic.
• Regional lymphadenopathy and lymphangitic streaks occur.
• Differential diagnosis: cellulitis, contact dermatitis, herpes zoster (prodromal), angioedema, erythema migrans, acute lupus erythematosus (face), necrotising fasciitis, DVT and stasis dermatitis.
• Complications: abscess, necrosis, bacteraemia, septic shock, streptococcal toxic shock, post-streptococcal glomerulonephritis, thrombophlebitis, chronic lymphoedema and recurrence. In facial disease, orbital cellulitis and cavernous sinus thrombosis are possible.

• The diagnosis is clinical. Mark the border.
• Tests are needed in moderate or severe illness: full blood count (neutrophilia), CRP (often above 50 mg/L), urea, creatinine, glucose and lactate. Anti-streptolysin O or anti-DNase B titres can support recent group A streptococcal infection but are rarely needed.
• Blood cultures are positive in fewer than 5%, and are indicated in sepsis, immunosuppression or lymphoedema. Swab any wound or bulla fluid.
• Examine for the portal of entry: toe webs, nose, ear, wounds.
• Ultrasound if abscess or deep vein thrombosis is suspected. Urinalysis for blood and protein if post-streptococcal glomerulonephritis is suspected 1 to 3 weeks later.
• Red flags for necrotising infection and the need for urgent surgical review are pain out of proportion, rapid progression, haemorrhagic bullae, crepitus and shock.

• Mild to moderate disease, oral therapy for 5 to 7 days, extended to 10 to 14 days if resolution is slow:
  • Phenoxymethylpenicillin 500 mg to 1 g orally 6 hourly. Child: 12.5 mg/kg 6 hourly (maximum 500 mg per dose in smaller children).
  • Amoxicillin 500 mg to 1 g orally 8 hourly. Child: 25 mg/kg 8 hourly.
  • Flucloxacillin 500 mg to 1 g orally 6 hourly if S. aureus is possible.
  • Penicillin allergy: clarithromycin 500 mg orally 12 hourly, clindamycin 300 to 450 mg orally 8 hourly, or cefalexin 500 mg 6 hourly if the reaction was not severe.
• Severe disease, facial involvement with systemic signs, infants, or failed oral therapy: admit and give intravenous therapy:
  • Benzylpenicillin 1.2 to 2.4 g IV 4 to 6 hourly (child 50 mg/kg 6 hourly, maximum 2.4 g), with flucloxacillin 1 to 2 g IV 6 hourly if staphylococcal infection is possible.
  • Cefazolin 1 to 2 g IV 8 hourly.
  • Add clindamycin 600 to 900 mg IV 8 hourly for toxin suppression if streptococcal toxic shock or necrotising infection is suspected.
  • Switch to oral therapy when afebrile and improving for 24 to 48 hours.
• Supportive measures: elevate the limb, give paracetamol 1 g orally 6 hourly (maximum 4 g per day), rest, hydrate, treat tinea pedis, fissures and nasal infections, and use compression once pain and infection have settled. Give prophylactic dose low molecular weight heparin in admitted immobile patients.
• Facial erysipelas: check vision and eye movements, and obtain CT if orbital extension or cavernous sinus thrombosis is suspected.
• Special groups:
  • Pregnancy: penicillins and cefalexin are suitable. Avoid tetracyclines and fluoroquinolones.
  • Children: weight based dosing as listed for each drug, with early admission for infants.
  • Renal impairment: adjust beta lactam doses to creatinine clearance.
  • Elderly and diabetic: lower the threshold for admission, and optimise glycaemic control.
• Prevention of recurrence in patients with 2 or more episodes in a year:
  • Benzathine benzylpenicillin 1.2 million units IM every 4 weeks (every 2 to 3 weeks if relapses continue; evidence for the shorter interval is limited).
  • Alternatively phenoxymethylpenicillin 250 to 500 mg orally 12 hourly.
  • In penicillin allergy: erythromycin 250 mg orally 12 hourly.
  • Continue for at least 6 to 12 months and review yearly. Protection ends when the drug stops, and about 45% relapse after discontinuation.
  • Manage lymphoedema with compression, skin care and weight loss.
• Failure to respond at 48 to 72 hours: confirm the diagnosis, exclude abscess, DVT and necrotising infection, check for MRSA or an alternative cause, and consider surgical review.
• Follow up: review at 1 to 2 weeks, check urine for haematuria and blood pressure if new oedema or dark urine appears, and refer persistent recurrent disease for lymphoedema or dermatology assessment.