Cellulitis is an acute infection of the dermis and subcutaneous tissue. It is a common cause of inpatient hospital admissions, accounting for 10% of infectious disease-related US hospitalizations from 1998 to 2006.6
Most cases of cellulitis are caused by S. aureus and group A Streptococcus.7 However, in certain situations other organisms may be involved, such as gram-negative organisms in cellulitis originating from a toe web fissure or Hemophilus influenza in young infants.
Risk factors for cellulitis include skin trauma or an underlying lesion such as a leg ulcer or fissured toe webs that can serve as a portal of entry for pathogenic bacteria. Other risk factors include chronic venous or arterial insufficiency, edema, surgery, intravenous drug use, body piercing, human and animal bites, diabetes, hepatic cirrhosis, immunosuppression, and neutropenia.6,8
Cellulitis typically presents with rubor (erythema), dolor (pain), calor (warmth), and tumor (edema).
Cellulitis typically begins with the acute onset of localized erythema and tenderness. The borders may be ill-defined and surface crusts may develop (Figure 12-3). Other symptoms include fever, malaise, and chills. Less common findings include ascending lymphangitis and regional lymphadenopathy. Cellulitis usually presents in a unilateral distribution. Some other clinical presentations of less common types of cellulitis are listed in Table 12-1.
Cellulitis on leg of diabetic patient. Warm tender areas of erythema on foot and leg.
Less common types of cellulitis.
||Download (.pdf) Table 12-1.
Less common types of cellulitis.
|Types of Cellulitis ||Presentation ||Organism(s) |
|Erysipelas ||Sharply defined red, edematous plaque, usually on face or legs ||Group A, or less commonly B, C, or G streptococci or rarely S. aureus |
|Periorbital (preseptal) cellulitis ||Painful erythema and edema on the eye lids and periorbital area, more common in children ||S. aureus, Streptococcus pyogenes, Hemophilus influenzae |
|Ecthyma gangrenosum ||Painful blue-grey thick eschar over an ulcer in an immunocompromised patient ||Pseudomonas aeruginosa |
|Perianal cellulitis (dermatitis) ||Sharply marginated bright red, painful erythema surrounding the anus. More common in young children ||Streptococcus pyogenes |
|Streptococcal intertrigo ||Similar presentation to perianal strep cellulitis, but it occurs in body fold areas such as the axillae and inguinal area ||Streptococcus pyogenes |
|Crepitant cellulitis (gas gangrene) ||Rapid development of edema, crepitus, and bullae ||Clostridia species usually C. perfringens |
|Gangrenous cellulitis (necrotizing fasciitis) ||Indurated painful erythema with bullae (Figure 12-4) quickly progressing into a large black eschar and necrosis of the skin, fascia, or muscle ||Polymicrobial including Group A Streptococcus and anerobes |
Necrotizing fasciitis on hand. Sudden onset of painful area with erythema, edema, and bullae.
The diagnosis of cellulitis is generally made in the clinical setting. If indicated, cultures from exudate or blistered areas can be done with a culturette swab or cultures can be obtained by aspirating the affected skin. A skin punch biopsy of affected skin may also be cultured. However, these techniques often do not isolate the pathogenic organism.9 If cultures are positive, they usually show gram-positive microorganisms, primarily Staphylococcus aureus, group A or group B streptococci, Streptococcus viridans, Streptococcus pneumoniae, Enterococcus faecalis, and, less commonly, gram-negative organisms such as Hemophilus influenzae and Pseudomonas aeruginosa.8,9
The key diagnostic clinical feature of cellulitis is a painful, warm, red, edematous plaque.
✓ Acute allergic contact dermatitis: Usually presents with pruritic, but not painful red plaques, with more than one area involved.
✓ Stasis dermatitis: Presents with bilateral chronic dermatitis on the lower legs, with red/brown pigment.
✓ Thrombophlebitis/deep vein thrombosis (DVT): Presents with calf pain, erythema, usually no fever or chills, abnormal ultrasound of the leg veins.
✓ Other: Insect bite, erythema migrans, erythema nodosum, Sweet's syndrome, panniculitis, eosinophilic cellulitis, fixed drug eruption, lipodermatosclerosis, and polyarteritis nodosum.
Treatment for the most common forms of cellulitis that is likely caused by methicillin-sensitive Staphylococcus aureus includes empiric treatment with a penicillinase-resistant penicillin, first-generation cephalosporin, amoxicillin-clavulanate, a macrolide, or a fluoroquinolone antibiotic.8,9 Treatment for MRSA and other organisms and other forms of cellulitis are summarized in references 8 and 9.
Localized disease can be treated in the outpatient setting, whereas extensive disease requires intravenous administration in an inpatient setting. Ancillary measures include elevation and immobilization of the involved limb to reduce swelling. One should also identify and treat the underlying portal of entry of the cellulitis (eg, tinea pedis, leg ulcer). Imaging studies may be needed, if crepitant or necrotic cellulitis is suspected.
Indications for Consultation
Severe or persistent disease that does not respond to treatment. Patients with high fevers, crepitant, or necrotic cellulitis should be hospitalized.