Cellulitis

Section: Skin and soft tissue Sub-section: Skin infections and breakdown Curriculum: Curriculum, page 53

Definition

• Infective spreading inflammation of the skin and subcutaneous tissues
• Resulting in pain, erythema, oedema & warmth

Incidence

• Common; in US 2-3 cases per 100 per year
• M > F
• Peak age 45-64

Classification

• Simple cellulitis
• Erysipelas:
  • Caused by Strep erythrotoxins
  • Affects the upper dermis and extends into the superficial cutaneous lymphatics
  • Red, hot, tender, oedematous skin
  • Toxic striations
  • Local lymphadenopathy with a raised border + toxic pt
  • Admit these patients

Aetiology

• Bacteria:
  • Group A Streptococcus (pyogenes) & Staphylococcus aureus most common
    • Violaceous colour & bullae suggests Strep infection
  • Haemophilus influenza in children
  • Fungi occasionally, especially immunocompromised
• Breach of skin from
  • Minor trauma
  • Post-surgical wounds / luer sites
• Contributing factors
  • DM
  • Immunodeficiency
  • Impaired circulation – PVD or impaired venous stasis
  • Lymphoedema
  • Pre-existing skin conditions: psoriasis, eczema

Clinical

• Skin erythema, warm, pain
• If crepitus → concerns for fasciitis, gangrene
• Lymphatic tracking → Lymphangitis
  • ± Systemic unwellness

Pathology and Investigations

• Pathology
  • Disrupted skin
  • Bacteria invade
  • Infection triggers an inflammatory response
• Investigations
  • FBC, CRP ± blood cultures
  • Areas of abscess or bullae may be cultured
    • → 90% positive yield
  • Usually no USS or x-ray required

Management

• Flucloxacillin
  • If clinically well – can manage as outpatient
  • If signs of SIRS or worse – admit
• Severe or not responding
  • Add Clindamycin
• Diabetic
  • Consider broader spectrum
  • Ceftriaxone (improved profile against gram negatives but not as good against gram positive & doesn’t cover pseudomonas)
  • Imipenem, Meropenem
  • Others – Penicillin, augmentin, ciprofloxacin
  • No advantage in adding benzylpenicillin to iv flucloxacillin

Prognosis / Natural Hx

• Good prognosis; most resolve with Abs

Specific Infections

Bacterial

Impetigo

• Children
• Staph, strep or both
• Vesicles, yellow crusting lesions

Folliculitis

• Infection of hair follicle
  • Furuncle or boil
• Multiple – carbuncle
• Staph aureus
• Intense inflammatory reaction,
• FB granulomatous reaction

Scalded Skin Syndrome

• Children
• Staph infection (phage type 71)
• Toxin = Epidermal splitting
• Peeling and pain

Viral

Verruca Vulgaris

• Common wart
• Skin or mucous membranes
• HPV
  • Types 1,2,4,26,29
• Hyperplasia of epithelium and hyperkeratosis
• Viral inclusion bodies in epidermis

Molloscum Contagiosum

• Pox virus
• Children
• Skin or mucous membranes
  • Pearly pink elevated papules, central punctum
• Single lesions require biopsy
  • Characteristic inclusion bodies
  • Eosinophilic at base of dermis, basophilic at surface
• Involute and disappear 2/12
• Common in AIDS - 10-20% affected