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Inflamed skin lesions on legs

Reviewed by Brian S. Kim, MD

Dr. P. Marazzi/Science Source

An 11-year-old boy presents with diffuse, inflamed lesions on both shins. His mother first noticed the abrasions when he was scratching them to the point where they bled. He doesn't remember any insect bites, but as a catcher on his Little League baseball team, he noticed that the lesions are always worse after a game and after practice. He is generally healthy and of normal weight for his height. He has no history of allergies or asthma.

What is the diagnosis?

Atopic dermatitis

Contact urticaria

Superinfected eczema

Wiskott-Aldrich syndrome

Superinfected eczema is an inflammation of the skin accompanied by itchy, weeping, oozing lesions. Secondary infection of the open skin can occur as a result of scratching. In this case, the infection was a consequence of sensitivity to wearing shin pads.

Although superinfected eczema is a complication of eczema, it can produce separate challenges. With damaged protective skin function and disturbance of quantity and quality of skin lipids, patients with eczema may have secondary bacterial infections. Staphylococcus aureus organisms are the most common etiologic agents; up to 90% of patients with eczema have staphylococcal colonization. Streptococcus is less commonly a cause. The progression from colonization to infection often is associated with a flare of eczema, and increased severity of the eczema is associated with more colonization. More erythema may be noted when the infection begins; then, the affected areas become encrusted or show a serous drainage. A clinical clue to superinfection of any kind is when patients stop responding to therapies that they are normally responsive to (eg, topical steroids).

With the recent increase in methicillin-resistant S. aureus (MRSA), treatment of a secondary infection of eczema with these organisms can be tricky. Patients with eczema and secondary bacterial skin infections should be treated with topical steroids or other anti-inflammatory medications and moisturizers to repair the skin barrier. The level of skin colonization with S. aureus is decreased with use of these agents alone. Topical or systemic antibiotics appropriate for specific or community-based sensitivities may be needed in severe infections.

Because of the damaged protective skin function, cutaneous inoculation of herpes simplex virus (HSV) can occur. Eczema herpeticum, or HSV-associated Kaposi varicelliform eruption, describes eczema secondarily infected with HSV (type 1 or type 2). The eczema may become more erythematous; then, vesicles develop that are arranged in a grouped pattern. Accompanying symptoms include fever, malaise, and lymphadenopathy. The condition can be diagnosed by a Tzanck smear (seeking multinucleated giant cells), a fluorescent antibody smear, or culture of a vesicular lesion. Patients with eczema herpeticum should be treated with acyclovir. More severe involvement may require hospitalization and use of systemic antivirals. In addition, topical steroids and moisturizers should be continued to repair the skin barrier.

Children with eczema are more likely than adults to acquire molluscum contagiosum infection, and the disease tends to be widespread. The lesions are generally smooth papules, sometimes with umbilicated skin. The lesions can spread by auto-inoculation to surrounding areas. Molluscum dermatitis accompanies 10% of molluscum lesions, and the dermatitis can be difficult to distinguish from eczema lesions. Untreated, molluscum lesions may resolve on their own; if necessary, the lesions can be treated with cantharidin, liquid nitrogen, or curettage.

Molluscum dermatitis is treated with topical steroids. Early recognition of infections associated with a diagnosis of eczema is critical for timely initiation of appropriate treatment.

Brian S. Kim, MD, Associate Professor, Department of Medicine, Division of Dermatology, Washington University School of Medicine, St. Louis, Missouri

Brian S. Kim, MD, has disclosed no relevant financial relationships.

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