DESCRIPTION

• Acute bacterial infection of the dermis and subcutaneous tissue
• Types and locations:
  • Most common on lower extremities, unilateral
  • Periorbital cellulitis: infection of the eyelid and surrounding tissues
  • Orbital cellulitis: infection of the eye posterior to the septum; most common risk factor is sinusitis.
  • Facial cellulitis: preceded by URI or otitis media
  • Buccal cellulitis: infection of cheek in children associated with bacteremia (common before Haemophilus influenzae type B vaccine)
  • Peritonsillar cellulitis: common in children; associated with fever, sore throat, and “hot potato” speech
  • Perianal cellulitis: sharply demarcated, bright, perianal erythema
  • Necrotizing cellulitis: gas-producing bacteria in the lower extremities; more common in diabetics

EPIDEMIOLOGY

• Predominant sex: male = female
• Increased hospitalizations for cellulitis in the summer and fewer in the winter months

ETIOLOGY AND PATHOPHYSIOLOGY

Caused by bacterial penetration through a compromise in the epidermis into the deep dermis and subcutaneous tissues.

• Microbiology
  • β-Hemolytic streptococci (groups A, B, C, G, and F), staphylococci (Staphylococcus aureus, including MRSA) and gram-negative aerobic bacilli most common
  • S. aureus seen in periorbital and orbital cellulitis and people who inject IV drugs
  • Pseudomonas aeruginosa seen in diabetics and other immunocompromised patients
  • H. influenzae causes buccal cellulitis.
  • Clostridia and non–spore-forming anaerobes: necrotizing cellulitis (crepitant/gangrenous)
  • Streptococcus agalactiae: following lymph node dissection
  • Pasteurella multocida and Capnocytophaga canimorsus: precipitated by bites
  • Streptococcus iniae: immunocompromised hosts
  • Rare causes: Mycobacterium, fungal (mucormycosis, aspergillosis)

RISK FACTORS

• Disruption of skin barrier from trauma, infection, insect bites, injection drug use, body piercing, maceration, ulcerations, chronic wounds, fissured toe webs
• Inflammation from excoriating skin disorders or radiation therapy
• Edema due to venous insufficiency; lymphatic obstruction due to surgery or congestive heart failure
• Advanced age, male gender, diabetes, hypertension (HTN), cancer, obesity
• Dermatomycosis, tinea pedis, onychomycosis, presence of S. aureus and/or streptococci in toe webs
• Previous episode of cellulitis
• Recurrent cellulitis:
  • Cellulitis recurrence score (predicts recurrence of lower extremity cellulitis based on presence of lymphedema, chronic venous insufficiency, peripheral vascular disease, and deep venous thrombosis)
  • Recurrent cellulitis is seen in immunocompromised patients (HIV/AIDS), steroids and TNF-α inhibitor therapy, diabetes, hypertension, cancer, peripheral arterial or venous diseases, chronic kidney disease, dialysis, IV or SC drug use.

GENERAL PREVENTION

• Good skin hygiene and hydration to avoid dryness and cracking
• Management of edema with elevation, compression stockings, pneumatic pressure pumps
• Maintain glycemic control and proper foot care in diabetic patients.

COMMONLY ASSOCIATED CONDITIONS

Abscess, lymphedema, venous insufficiency, stasis dermatitis, obesity