Cellulitis

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Authored by Danny Lee Curtis, MD, Consulting Staff, Department of Emergency Medicine, Community Hospital of New Port Richey

Danny Lee Curtis, MD, is a member of the following medical societies: American Academy of Emergency Medicine

Edited by Mark Louden, MD, FAAEM, Consulting Staff, Department of Emergency Medicine, Saint Francis Medical Center; Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine; Barry J Sheridan, DO, Chief, Department of Emergency Medical Services, Brooke Army Medical Center; John Halamka, MD, Chief Information Officer, CareGroup Healthcare System, Assistant Professor of Medicine, Department of Emergency Medicine, Beth Israel Deaconess Medical Center; Assistant Professor of Medicine, Harvard Medical School; and Barry Brenner, MD, PhD, Vice-Chair, Director, Division of Research, Associate Clinical Professor, Department of Emergency Medicine, Cornell University, Brooklyn Hospital Center 

Background: The word cellulitis literally means inflammation of the cells. It generally indicates an acute spreading infection of the dermis and subcutaneous tissues resulting in pain, erythema, edema, and warmth. 

Pathophysiology: Skin and subcutaneous tissues are involved when microorganisms invade disrupted skin. 

Frequency:

• In the US: Cellulitis is a common infection. 

Mortality/Morbidity: Cellulitis may progress to serious illness by uncontrolled spread contiguously or via the lymphatic or circulatory systems. 

Race: No predilection exists. 

Age: No predilection for age is known except as noted for facial cellulitis and perianal cellulitis. 

• Facial cellulitis occurs more commonly in adults older than 50 years and in children aged 6 months to 3 years. 
  
• Perianal cellulitis occurs predominantly in children. (This is somewhat of a misnomer, and the term perianal disease is preferred by some authors.) 

History: Patient may have a history of trauma or surgery, causing a break in the skin, or may have no discernible dermal injury. The infection typically develops over a period of several days.

• Among those with peripheral vascular disease or diabetes, minor injuries or cracked skin in the feet or toes can serve as a source for infection. 
  
• Foreign bodies passing through skin, such as intravenous catheters or orthopedic pins, can provide a portal of entry to infection. 
  
• In those with prior surgery involving lymph node dissection, such as mastectomy, no evidence of recent injury may be observed. However, these patients are prone to recurrent cellulitis in these areas. 

Physical: Hallmarks of cellulitis include the following: 

• Warmth, erythema, edema, and tenderness of affected area are present. 
  
• Associated red streaking visible in skin proximal to the area of cellulitis is characteristic of ascending lymphangitis. In lymphangitis the infection is carried through the lymphatic system. 
  
  • Regional lymphadenopathy may be present. 
  • The margin of cellulitis will not be palpable.
  • Fever may be present. 
  • Cellulitis characterized by violaceous color and bullae suggests infection with Streptococcus pneumoniae (pneumococcus). 

Causes: 

• Bacterial and fungal infections 
  
  • In individuals with normal host defenses, the most common causative organisms are group A streptococci and Staphylococcus aureus. 
  • Cellulitis in infants may present as sepsis, most commonly caused by group B streptococci. 
  • In immunocompromised hosts, gram-negative rods or fungi may cause cellulitis, though fungal cellulitis is rare. 
  • Wounds occurring after exposure to fresh water may be caused by Aeromonas hydrophila, a gram-negative rod. 
  • Pneumococcus may cause a particularly malignant form of cellulitis, typically in an immunocompromised host, and frequently is associated with tissue necrosis, suppuration, and blood stream invasion. 
• Patients with the following conditions are at increased risk of developing serious or rapidly spreading cellulitis:
  
  • Diabetes 
  • Immunodeficiency 
  • Other systemic illness
  • Varicella  
  • Impaired peripheral circulation (arterial insufficiency or venous stasis) 
  • Lymphadenectomy following tumor excision, such as mastectomy 
  • Postvenectomy status following saphenous vein stripping 
   
• Chronic steroid use increases the risk of cellulitis. 
• Cellulitis may complicate varicella. 
  
  • Cellulitis may be identified by a margin of erythema surrounding the vesicles.
  • Though varicella is a viral illness and does not respond to antibiotics, the development of cellulitis complicating varicella mandates antibiotic treatment and careful clinical follow-up. Untreated cellulitis in association with varicella may progress to severe disfiguring gangrene of the dermal structures requiring skin grafting. Deaths have been reported.