Cellulitis
BASICS
Skin and soft tissue infections (SSTIs) are a common health burden with approximately a quarter of patients requiring hospitalization, leading to >650,000 admissions per year in the United States.
DESCRIPTION
- Acute bacterial infection of the dermis and subcutaneous tissue
- Types and locations:
- Most common on lower extremities, unilateral
- Periorbital cellulitis: infection of the eyelid and surrounding tissues
- Orbital cellulitis: infection of the eye posterior to the septum; most common risk factor is sinusitis.
- Facial cellulitis: preceded by URI 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
- 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
- Increased hospitalizations for cellulitis in the summer and fewer in the winter months
Incidence
1.5 to 24.6 per 1,000 person-years with recurrence rate ranging from 16% to 53% within 3 years.
Prevalence
Visits to U.S. ambulatory practices for purulent SSTI range from 5.4 to 11.3 million visits annually.
ETIOLOGY AND PATHOPHYSIOLOGY
Caused by bacterial penetration through a compromise in the epidermis into the deep dermis and subcutaneous tissues.
- Microbiology
- β-Hemolytic streptococci (groups A, B, C, G, and F), staphylococci (Staphylococcus aureus, including MRSA) and gram-negative aerobic bacilli most common
- S. aureus seen in periorbital and orbital cellulitis and people who inject IV drugs
- Pseudomonas aeruginosa seen in diabetics and other immunocompromised patients
- H. influenzae causes buccal cellulitis.
- Clostridia and non–spore-forming anaerobes: necrotizing cellulitis (crepitant/gangrenous)
- Streptococcus agalactiae: following lymph node dissection
- Pasteurella multocida and Capnocytophaga canimorsus: precipitated by bites
- Streptococcus iniae: immunocompromised hosts
- Rare causes: Mycobacterium, fungal (mucormycosis, aspergillosis)
Genetics
None
RISK FACTORS
- Disruption of skin barrier from trauma, infection, insect bites, injection drug use, body piercing, maceration, ulcerations, chronic wounds, fissured toe webs
- Inflammation from excoriating skin disorders or radiation therapy
- Edema due to venous insufficiency; lymphatic obstruction due to surgery or congestive heart failure
- Advanced age, male gender, diabetes, hypertension (HTN), cancer, obesity
- Dermatomycosis, tinea pedis, onychomycosis, presence of S. aureus and/or streptococci in toe webs
- Previous episode of cellulitis
- 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)
- 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.
GENERAL PREVENTION
- Good skin hygiene and hydration to avoid dryness and cracking
- Management of edema with elevation, compression stockings, pneumatic pressure pumps
- Maintain glycemic control and proper foot care in diabetic patients.
COMMONLY ASSOCIATED CONDITIONS
Abscess, lymphedema, venous insufficiency, stasis dermatitis, obesity
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