Description

• An acute bacterial infection of the dermis and subcutaneous (SC) tissue
• Types and locations:
  • Periorbital cellulitis: bacterial infection of the eyelid and surrounding tissues (anterior compartment)
  • Orbital cellulitis: infection of the eye posterior to the septum; sinusitis is most common risk factor.
  • Facial cellulitis: preceded by upper respiratory infection 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
  • Abdominal wall cellulitis: common in morbidly obese patients
  • 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
• Seasonality increased hospitalizations for cellulitis in the summer with fewer in the winter months (2).

Incidence
200/100,000 patient/years

• The exact prevalence is uncertain because cellulitis is common and not reportable. It affects all age groups and all races; however, certain types of cellulitis/microorganisms occur in certain populations.
• In the United States, ~14.5 million annual cases of cellulitis account for $3.7 billion in ambulatory costs (1).
• Cellulitis accounts for ~1.4% of hospitalizations in the U.S. and is associated with $5.5 billion in yearly costs (3).

Etiology and Pathophysiology

Cellulitis is caused by bacterial penetration through a compromise in the epidermis, the protective barrier of the skin.

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

Genetics
No genetic pattern

Risk Factors

• Disruption of skin barrier: trauma, infection, insect bites, injection drug use, body piercing
• Inflammation: eczema or radiation therapy
• Edema due to venous insufficiency; lymphatic obstruction due to surgery or congestive heart failure (CHF)
• Elderly, diabetes, hypertension, obesity
• 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) (4)[A]
  • 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 (4).

General Prevention

• Good skin hygiene
• Support stockings to decrease edema
• Maintain tight glycemic control and proper foot care in diabetic patients.

Commonly Associated Conditions

Abscess