- 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).
- 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.
- 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.
- 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.
- 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
- Usually from local trauma (scratch, impetigo, eczema, excoriated varicella)
- Hematogenous spread is very uncommon.
- Rarely associated with infectious conjunctivitis
- Commonly associated with severe sinusitis
- Less commonly: dental abscess, trauma, hematogenous spread
- Buccal: usually from local trauma; hematogenous seeding also very rare
- Commonly due to GABHS pharyngitis
- Cellulitis may progress to a peritonsillar abscess.
- Extremity: usually secondary to local trauma
- Breast: usually with mastitis (neonates)
- 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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