Children with AD: high risk of bacterial infections in carriers of a filaggrin gene variant

Superinfections are the most common complications in atopic dermatitis (AD). When lesions become excoriated, they act as a gateway for the entry of infectious agents. Furthermore, a disruption of the normal skin microbiome contributes to infections.

As Prof. Alina Suru (Carol Davila University of Medicine and Pharmacy, Romania) pointed out, patients with AD have an increased risk of infection due to defects in the skin and further cutaneous innate and adaptive immune abnormalities with type-2 inflammation. Staphylococcus aureus colonisation and cutaneous dysbiosis are additional factors that leave AD patients prone to infections [1]. AD-associated skin infections can progress to systemic complications such as sepsis, endocarditis, and septic arthritis. Whereas infectious complications must be treated with antibiotics, it is controversial whether to use antibiotics simply in exacerbations of AD [2]. Up to 90% of patients with AD are colonised by S. aureus, but it is difficult to distinguish between colonisation and infection. When commensal bacteria of the skin decrease, the virulence of S. aureus is enhanced, as commensal bacteria modulate the immune system to minimise inflammation and outcompete pathogens like S. aureus [2,3].

A loss-of-function variant in the filaggrin gene is associated with early-onset AD. “Patients with this gene variant have a 7 times higher risk of having 4 or more episodes of skin infections requiring antibiotics than those without the variant,” Prof. Suru explained.

AD flares can mask bacterial infections

Bacterial infections in paediatric AD can manifest as impetigo, cellulitis, erysipelas, and skin abscesses. In S. aureus infections, honey-coloured crusts and pustules are evident, whereas ß-haemolytic streptococcus present as well-defined, bright red erythema, thick-walled pustules, and heavy crusting [2,3]. “Things are complicated by the fact that features of flared AD such as increased erythema can mask or resemble signs of infections,” Prof. Suru said.

Bacterial infections can be managed by topical or systemic treatment, such as fusidic acid or mupirocin in localised infections, and systemic antibiotics, such as cephalexin, if the lesions are spread out over the body. If the infection is invasive, intravenous antibiotics are indicated, and in the case of methicillin-resistant Staphylococcus aureus (MRSA), antibiotics to which the organism is sensitive should be used [4].

Prof. Suru concluded that the best way to prevent skin infections in AD patients is to eliminate predisposing factors by improving skin barrier defects and by sufficient anti-inflammatory maintenance medication (see Figure).

Figure: The risk of skin infections can best be minimised by skin barrier improvement and anti-inflammatory therapy [1]

1. Suru A. Infectious complications in paediatric atopic dermatitis. FS6, SPIN 2022 Congress, 06–08 July, Paris, France.
2. Alexander H, et al. Br J Dermatol. 2020;182:1331-42.
3. Wang V, et al. Ann Allergy Asthma Immunol. 2021;126:3-12.
4. Ring J, et al. J Eur Acad Dermatol Venereol. 2012;26:1045-60.

 

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Posted on 26 August 2022