Erysipelas (St. Anthony’s Fire)

Info & Pathophysiology

Source: OpenI (NLM)

What is it?

Nonpurulent, upper dermal infection (can affect superficial lymphatics), with defined borders; mostly affects lower extremities/face as worsened blood circulation and thus diminished movement of antibodies and immune factors

Acute and abrupt onset

Risk Factors: excising saphenous vein, lymphatic edema or obstruction, arteriovenous fistula, immunocompromised

Clinical presentation: erythematic raised rash; bullae if more extreme, milian’s ear sign (helps differential diagnosis between cellulitis, as ear does not have deeper dermal tissues)

Blood work: leukocytosis, elevated ESR/C-reactive protein

Pathophysiology:

  • Streptococci mediated infection
    • Group A beta-hemolytic/GABHS: facial
    • Non Group A: extremities
    • Infection via skin breaks (insect bites, ulceration, surgical incisions, venous insufficiency), colonizes lymph nodes, causing dermal edema

Differential Diagnosis: Erysipelas vs. Cellulitis

Erysipelas

Source: OpenI (NLM)

Infectious agent: most common agent is Group A Strep

Infection depth: limited to upper dermis and superficial lymphatics

Course of onset: acute and abrupt onset

Lesion characteristics: always nonpurulent, clear demarcation and often raised

If involves ear, will present with Milian’s Ear Sign

Cellulitis

Source: OpenI (NLM)

Infectious agent: Strep and S.aureus in equal incidence

Infection depth: infection extends all the way to deeper dermis and subcutaneous adipose tissue

Course of onset: indolent onset, slow development over a few days

Lesion characteristics: can be purulent (s.aureus) or nonpurulent (beta-hemolytic streptococci or MSSA), poor demarcation, no abscess or purulent discharge

Similarities

  • Both are bacterial skin infections
  • Both are erythematous, edematous, warm/hot to touch
  • Almost always unilateral in lower extremities
  • Similar risk factors (see above)
  • Diagnosis is mostly clinical

Treatment

If present with abscess: incision & drainage with first line antibiotics

  • GABHS: penicillin, amoxicillin, cefazolin, ceftriaxone

Hydration, cold compresses or other compression therapy to reduce swelling

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