Patient Story

A 4-year-old child presents with a fever and a red and swollen foot (Figure 120-1). The patient injured her foot 3 days before with a door. On physical examination, the foot was warm, tender, red, and swollen, and the child’s temperature was 39.4°C (103°F). This is classic cellulitis and the child was admitted for IV antibiotics.

Figure 120-1

Cellulitis of the foot after an injury with a door in a 4-year-old girl. (Courtesy of Richard P. Usatine, MD.)


Cellulitis is an acute infection of the skin that involves the dermis and subcutaneous tissues.


  • Facial cellulitis occurs more often in adults ages 50 years or older, or in children ages 6 months to 3 years.
  • Perianal cellulitis occurs more commonly in young children but can be seen in adults as well (see Chapter 111, Diaper Rash and Perianal Dermatitis).

Etiology and Pathophysiology

  • Often begins with a break in the skin caused by trauma, a bite, or an underlying dermatosis (e.g., tinea pedis, stasis dermatitis) (Figures 120-2, 120-3, 120-4).
  • Is most often caused by group A β-hemolytic Streptococcus (GABHS) or Staphylococcus aureus. The most common etiology of cellulitis with intact skin, when it has been determined through needle aspiration and/or punch biopsy, is S. aureus, outnumbering GABHS by a ratio of nearly 2:1.1

Figure 120-2

Cellulitis and abscess of the finger after a clenched fist injury in which the patient cut his finger on the tooth of the man he assaulted. (Courtesy of Richard P. Usatine, MD.)

Figure 120-3

Cellulitis of the foot of a diabetic person in which there is possible necrosis and gangrene of the second toe, requiring hospitalization and a podiatry consult. (Courtesy of Richard P. Usatine, MD.)

Figure 120-4

Cellulitis in an older man with venous stasis dermatitis. (Courtesy of Richard P. Usatine, MD.)

There are increasing concerns about the role of community- acquired methicillin-resistant S. aureus (MRSA) in all soft-tissue infections including cellulitis.25

  • After a cat or dog bite, cellulitis is often caused by Pasteurella multocida.
  • After saltwater exposure, cellulitis can be secondary to Vibrio vulnificus in warm climates (Figure 120-5). A Vibrio vulnificus infection can be especially deadly.

Figure 120-5

Fatal Vibrio vulnificus infection with widespread cellulitis and bullae. The violaceous bullae should be a red flag for this infection and/or necrotizing fasciitis. Even though the infection was identified early, the overwhelming sepsis resulted in death. (Courtesy of Donna Nguyen, MD.)

Erysipelas is a specific type of superficial cellulitis with prominent lymphatic involvement and leading to a sharply defined and elevated border (Figure 120-6).

Figure 120-6

Erysipelas of the central face that responded well to oral antibiotic therapy. (Courtesy of Ernesto Samano Ayon, MD.)

Jun 5, 2016 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Cellulitis
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