Cellulitis

Cellulitis is a topic covered in the 5-Minute Pediatric Consult.

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Basics

Description

  • Cellulitis is an acute, spreading pyogenic inflammation of the dermis and subcutaneous tissue, often complicating a wound or other skin condition.
  • Cellulitis may be further classified by the unique area of the body it affects (e.g., periorbital or orbital cellulitis, peritonsillar cellulitis).

Epidemiology

  • The most common cause of cellulitis in children is Staphylococcus aureus or Streptococcus pyogenes infection, which develop secondary to local trauma of the integument.
  • In purulent cellulitis (presence of a pustule, abscess, or purulent drainage), S. aureus infection is more likely.
  • Community-acquired methicillin-resistant S. aureus (CA-MRSA) infections continue to increase in incidence but more commonly cause purulent abscesses rather than cellulitis.
  • The prevalence of CA-MRSA among purulent skin and soft tissue infections is >60% in some communities.
  • Bacteremic disease is rare, owing to the tremendous efficacy of vaccines against both Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae.

General Prevention

  • Good wound care is paramount.
  • All wounds should be cleaned with soap and water and then covered with a clean, dry cloth.
  • Topical antibiotic ointment is optional with minor wounds.

Pathophysiology

  • Cellulitis usually occurs after local trauma that breaches in the integument (abrasions, lacerations, bite wounds, excoriated dermatitis, varicella, etc.).
  • Cellulitis may result from local invasion or infection (e.g., sinusitis leading to orbital cellulitis).
  • Hematogenous dissemination is rare.

Etiology

  • S. aureus: methicillin-susceptible S. aureus (MSSA) and MRSA.
  • Group A β-hemolytic streptococci (GABHS, or S. pyogenes).
  • S. aureus and S. pyogenes are by far the most common causes of uncompleted cellulitis.
  • S. pyogenes is also the usual cause of erysipelas, a superficial cellulitis.
  • S. pneumoniae (uncommon)
  • Group B streptococci (GBS) and gram-negative rods (GNRs): neonates
  • Hib (rare)
  • Pseudomonas aeruginosa and anaerobic bacteria: immunocompromised children
  • Pasteurella species: cat and dog bites
  • Eikenella corrodens: human bites

Commonly Associated Conditions

  • Periorbital
    • Usually from local trauma (scratch, impetigo, eczema, excoriated varicella)
    • Hematogenous spread is very uncommon.
    • Rarely associated with infectious conjunctivitis
  • Orbital
    • Commonly associated with severe sinusitis
    • Less commonly: dental abscess, trauma, hematogenous spread
  • Buccal: usually from local trauma; hematogenous seeding also very rare
  • Peritonsillar
    • Commonly due to GABHS pharyngitis
    • Cellulitis may progress to a peritonsillar abscess.
  • Extremity: usually secondary to local trauma
  • Breast: usually with mastitis (neonates)
  • Perianal
    • Seen in infants and young children
    • Etiology: GABHS
    • Perianal pain, pruritus, and erythema; sometimes associated with bloody stools
  • Cellulitis–adenitis syndrome
    • Neonates and infants
    • Etiology: GBS most common; S. aureus, GNRs
    • Bacteremia/meningitis commonly associated

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