Diagnosing Disseminated Bullous Staphylococcal Impetigo in Patients With Atopic Dermatitis

In patients with atopic dermatitis, clinicians should consider not only viral pathogens but also bacterial pathogens, according to a letter to the editor published in the Journal of the European Academy of Dermatology and Venereology.

Disseminated viral infections such as eczema herpeticatum, eczema vaccinatum, eczema molluscatum, or eczema coxsackium have been frequently reported in patients with atopic dermatitis. Bacterial skin infections, especially with Staphylococcus aureus, are regarded primarily as localized infections or impetiginization, and reported disseminated cases are rare.

“Recently, we have noticed several cases of disseminated bullous staphylococcal impetigo in atopic dermatitis patients,” wrote the study authors. “In analogy to the disseminated viral infections in atopic skin, the term ‘eczema staphylococcatum’ could be used.”

A 10-year-old boy with a history of atopic dermatitis was observed by the study authora. He presented with acute onset of a bullous rash and generalized erosions and yellow crusts with maximum involvement of the nape and the left antecubital area. Polymerase chain reaction test results were negative for herpes simplex virus 1 and 2. However, a bacterial smear was positive for S. aureus.

A second patient was a 24-year-old man with a history of atopic dermatitis who reported progressive skin changes in 1 week without any systemic symptoms. The patient had an eruption of flaccid superficial bullae, with moist, erythematous erosions, collarette scaling, and yellow crusts. The lesions originated and were accentuated on the face, neck, and both antecubital areas but rapidly disseminated to the trunk and both extremities. Laboratory examination results were normal except for a slightly increased C-reactive protein value (12.2 mg/L) and a positive antinuclear antibody titer (1:320).

“The diagnosis of disseminated bullous impetigo can be challenging, and initial misdiagnosis is common,” noted the researchers. “The most important differential diagnoses are impetiginized atopic dermatitis flare-up and eczema herpeticatum,” they stated. “However, in this context, it is essential to keep in mind that not every rash in atopic dermatitis patients is a flare-up, and not every blister on atopic skin is due to a herpes infection.”

For patients with localized impetigo, a topical therapeutic approach using antiseptics combined with topical antibiotics is usually sufficient, according to the investigators. “Good sensitivity has been shown for octenidine and chlorhexidine, and for retapamulin and mupirocin, although mupirocin should be reserved for nasal decolonization of methicillin-resistant S. aureus,” they commented.

In cases of disseminated or widespread bullous impetigo, additional oral antibiotics such as cephalexin or flucloxacillin are recommended, the researchers advised. They noted that clindamycin, macrolides, and especially amoxicillin/ampicillin should be avoided in uncomplicated cases due to high levels of resistance. In severe cases, the study authors recommend microbiological culture with antibiotic sensitivity testing to exclude methicillin-resistant S. aureus.

“After initial misdiagnosis, our 2 [patients] rapidly improved on oral cefalexin combined with octenidine wraps and chlorhexidine cream,” the researchers commented. “In conclusion, atopic dermatitis is well known for disseminated skin infections, and clinicians should consider not only viral but also bacterial pathogens.”

Reference

Koch L, Cerpes U, Binder B, Cerroni L. Disseminated bullous impetigo in atopic dermatitis (‘eczema staphylococcatum’). Published online November 20, 2020. J Eur Acad Dermatol Venereol. doi: 10.1111/jdv.17043