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Cellulitis & Erysipelas

❓What❓

  • Cellulitis: skin & soft tissue infection (SSTI) extending from epidermis → subQ tissue

  • Erysipelas: variant of cellulitis extending no further than the dermis

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❓Epidemiology❓

  • Cellulitis: middle-aged & elderly, extremely rare in UEs without trauma history (e.g. bite)

  • Erysipelas: young children & elderly, immunocompromised

  • Bacteremia: blood cultures positive in < 10% of cellulitis cases overall (i.e. should only be sent if high fevers or rigors)

❓Presentation❓

  • Cellulitis & Erysipelas: skin erythema, edema, & warmth +/- petechiae and/or hemorrhage → superficial bullae

  • Risk Factor: obesity, lymphedema & chronic venous stasis, pre-existing skin infection (e.g. tinea, varicella), skin barrier disruption (e.g. abrasion, penetrating wound, pressure ulcer, venous leg ulcer, insect bite), decompensated inflammatory dermatologic disease (e.g. eczema, psoriasis)

  • Systemic Inflammation (e.g. ↑ WBC, rigors): erysipelas > cellulitis, often preceding onset of dermatologic signature & being hyperacute in tempo in erysipelas

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  • Local Descriptor: erysipelas features clearly demarcated borders (due to discrete, dermal location) +/- lymphangitic spread

Left: following large veins (lymphangitic)

Right: sharp demarcations (discretely dermal)

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❓Diagnosis❓

  • Clinical

💊 Treatment 💊

Non-Diabetic SSTIs

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Diabetic SSTIs (IDSA 2023 Guidelines on DFI)

  • Mild: DFI is diagnosed if 2+ of following are present (local swelling/induration, local tenderness/pain, local warmth, purulent discharge, & erythema border > 0.5 cm but < 2 cm from wound margin)

  • Moderate: erythema extending 2+ cm from wound margin and/or infection involving tissue deeper than subcutaneous space (e.g. tendon, muscle, joint, bone)

  • Severe: any infection associated w/ 2+ SIRS findings (temperature derangements, tachycardia, tachypnea, WBC > 12,000, > 10% bands)
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Consideration of Osteomyelitis in DFI

  • Initial diagnostic assessment is based on combination of clinical findings, X-ray findings (both insensitive & non-specific), & ESR/CRP
  • If diagnostic uncertainty based on initial assessment, MRI is recommended, although MRI findings can also be non-specific (see notes on “osteomyelitis mimickers”)

⚪ Note: the most common findings suggestive of osteomyelitis (periosteal elevation) is neither sensitive nor specific (e.g. can be caused by stress fracture). The earliest bone change (marrow edema) is not detectable by X-ray. Sensitivity ↑ over time, when bone begins to collect erosions due to cortical destruction

📚 References 📚