FIGURE 66.6 Erysipelas (Reprinted with permission from Frontera WR FIMS Sports Medicine Manual Philadelphia, PA: Lippincott Williams & Wilkins; 2011.) Cellulitis Cellulitis is the acute presentation of red, painful, swollen skin that is caused by a localized bacterial infection in the dermis and subcutaneous tissue There may have been a break in the skin that leads to the infection but the infection then spreads underneath the skin Because the infection is within the skin, it is difficult to culture the pathogen Leading edge cultures have a low yield so most patients are treated empirically Patients with disruption of the skin barrier (e.g., tinea pedis or atopic dermatitis) or lymphatic disruption (postsurgical or from a congenital lymphatic abnormality) have a higher risk of cellulitis Erysipelas is a type of cellulitis that presents with swollen, red, painful edematous plaques due to infection of the superficial dermal lymphatics ( Fig 66.6 ) In erysipelas, there is often a step-off from affected edematous to normal skin The differential diagnosis of cellulitis includes contact dermatitis Contact dermatitis is often multifocal and itchy Looking for linear areas of redness or vesiculation can help favor a contact allergy Acute contact dermatitis of the face is often misdiagnosed as orbital or periorbital cellulitis Usually contact dermatitis is less painful to touch, may have crusting overlying the rash, and fever and eye pain should be absent The most common causes for cellulitis are GAS and SA (erysipelas is only caused by GAS) Vibrio vulnificus, often due to exposure to infected oysters or salt water, is a rare cause of bullous, often purpuric cellulitis Culture of blister fluid may yield the pathogen Erysipeloid is a localized eruption of purple macules and patches often on the hands or other exposed areas caused by exposure to Erysipelothrix rhusiopathiae, often while handling raw chicken or fish ( Fig 66.7 ) Therapy of erysipeloid is with a first-generation cephalosporin such as cephalexin Secondary Infection of Inflamed Skin Intertrigo describes inflamed, red skin folds that are a result of chronic irritation, yeast, or bacteria Streptococci or staphylococci can superinfect this inflamed skin and cause worsening pain, bright red erythema, and erosion in the skin fold Intertrigo can be multifocal and common areas include the inguinal folds (in association with perianal streptococcal infection), or neck folds in infants where saliva is trapped ( Fig 66.8 ) Patients with atopic dermatitis are often colonized with SA and have downregulated innate immunity and so when scratched the skin can become readily infected SA and GAS are the most common bacterial pathogens in superinfected atopic dermatitis Clinically, there may be pustules or just honey-colored crusts and erosions FIGURE 66.7 Erysipeloid (Reprinted with permission from Betts RF, Chapman SW, Penn RL Reese and Betts’ a Practical Approach to Infectious Diseases 5th ed Philadelphia, PA: Lippincott Williams & Wilkins; 2002.) Culture of the affected skin can yield the pathogen but caution is needed in interpreting these results as cultures will not differentiate colonization from true infection Therapy with topical mupirocin or bacitracin is often effective for bacterial intertrigo but systemic antibiotics such as cephalexin or clindamycin can be used in more extensive cases Other Pathogens Rocky Mountain Spotted Fever Rocky Mountain spotted fever (RMSF), one of the most virulent infections identified in humans, is caused by Rickettsia rickettsii transmitted by the bite of a tick (see Chapters 88 Dermatologic Urgencies and Emergencies and 94 Infectious Disease Emergencies ) Confirmed cases have been reported from all parts of the United States from varying tick vectors RMSF is associated with a fatality rate of 5% with antimicrobial treatment and 13% to 40% without therapy Patients who are treated with doxycycline by the fifth day of illness have the best survival FIGURE 66.8 Intertrigo PLEASE note, this is VERY likely a strep infection and not simple intertrigo (Reprinted with permission from Burkhart C, Morrell D, Goldsmith LA, et al VisualDx: Essential Pediatric Dermatology Philadelphia, PA: Lippincott Williams & Wilkins; 2009.) ... (Reprinted with permission from Burkhart C, Morrell D, Goldsmith LA, et al VisualDx: Essential Pediatric Dermatology Philadelphia, PA: Lippincott Williams & Wilkins; 2009.)