Impetigo (see Impetigo): infection of superficial layers of the epidermis
Cellulitis (see Cellulitis): skin infection of deeper dermis and subcutaneous fat (resulting from bacterial breach of the skin) characterized by erythema, warmth, and edema without an underlying suppurative focus
Erysipelas (see Erysipelas): skin infection of upper dermis and superficial lymphatics (resulting from bacterial breach of the skin) characterized by erythema, warmth, and edema without an underlying suppurative focus
Furuncle (Boil) (see Skin Abscess): infection of hair follicle where purulent material extends through the dermis into the subcutaneous tissue, forming a small abscess
Carbuncle (see Skin Abscess): coalescence of several inflamed follicles into a single inflammatory mass with purulent drainage from multiple follicles
Skin Abscess (see Skin Abscess): collection of pus within dermis and deeper skin tissues
Necrotizing Soft Tissue Infection (see Necrotizing Soft Tissue Infection): deep tissue infection involving the hypodermis (and contained structures)
All of These are Characterized by Fulminant Tissue Destruction, Systemic Toxicity (Tachycardia >120 Beats/min, Hypotension, Elevated Creatine Kinase, CRP >15 mg/dL, LRINEC Score >6, etc), and High Mortality Rates
Predisposing Factors
Local Factors
Skin Barrier Disruption: penetrating wound, IV drug abuse, etc
Sensitivity/Specificity: only positive in 20-30% of cases
Suggests that relatively small numbers of bacteria may result in significant inflammation with most of the observed findings being due to the host inflammatory response
Usually not performed
Needle Aspiration of Bullae
Sensitivity/Specificity: positive in <5-40% of cases
Suggests that relatively small numbers of bacteria may result in significant inflammation with most of the observed findings being due to the host inflammatory response
Indications for Needle Aspiration of Bullae
Extensive Skin Involvement
Recurrent/Persistent Infection
Specific Exposures: animal bite, water-associated injury
Specific Host Factors: lymphedema, malignancy, neutropenia, immunosuppression/immunodeficiency, splenectomy, diabetes
Systemic Toxicity
X-Ray/CT/MRI
May be useful in some cases to exclude skin abscess or to distinguish cellulitis/erysipelas from osteomyelitis or gas gangrene
However, radiologic exams cannot reliably differentiate cellulitis from necrotizing fasciitis or gas gangrene and these should not delay surgical intervention if necrotizing fasciitis or gas gangrene are suspected
Clinical Manifestations
Radiologic Presence of Soft Tissue Gas May Allow Clinical Differentiation of Necrotizing Soft Tissue Infections (NEJM, 2017) [MEDLINE]
Dermatologic Manifestations
Skin Erythema, Warmth, and Edema without an Underlying Suppurative Focus, with Lesions That are Characteristically Raised Above the Level of the Surrounding Skin: with clear line of demarcation between involved and uninvolved skin
Most Common Site of Involvement: lower extremities
Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America. Clin Infect Dis. 2014 Jul 15;59(2):e10-52. doi: 10.1093/cid/ciu444 [MEDLINE]