Cellulitis

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Basics

A common global health burden with >650,000 admissions per year in the United States alone (1)

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

Prevalence
  • 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).

Etiology and Pathophysiology

Cellulitis is caused by bacterial penetration through a break in the skin. Hyaluronidase mediates SC spread.

  • Microbiology
    • β-Hemolytic streptococci (groups A, B, C, G, and F), Staphylococcus aureus, including 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) (3)[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 (3).

General Prevention

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

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