Pediatric emergency medicine trisk 318

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.)