Severe Childhood Atopic Dermatitis : Epidemiological and Clinical Features, and Associated Factors in Brazzaville (Congo)

Introduction

Atopic dermatitis (or atopic eczema) is the commonest inflammatory skin disease that is characterised by intense pruritis and recurrent eczematous lesions [1, 2]. The overall prevalence of atopic dermatitis (AD) in children ranges from 10% to 20% across studies with a wide geographic variety [3, 4]. Prevalence and incidence of AD varies from country to country and geographically within a country [5]. The disease manifests during the first year of life, but it can start at any age. The diagnosis relies exclusively on clinical features. No specific laboratory or histological findings have been reported for its diagnosis [1].

The impact of AD on quality of life is similar to that caused by other chronic diseases such as asthma and diabetes [6]. In its moderate and severe forms, AD causes psychological disorders, anxiety, depression, low self- esteem, sleep disorders with repercussions on school performance and familial stress [2, 7].

Few data is available concerning epidemiology and the factors involved in severe AD. This gap remains a field of research [8]. In order to improve the quality of life of children with AD, the objectives of our study were to describe epidemiological and clinical aspects and to determine the factors associated with the severity of AD.

Patients and Methods

This was a bicentric, descriptive and analytic cross- sectional study conducted from January 2016 to December 2018 in Brazzaville (Congo) in two health facilities: Talangaï Reference Hospital in Dermatology and infectious diseases Department and Cogemo private Hospital.

The medical records of children aged between 1 month and 15 years, received for an atopic dermatitis, were collected. Incomplete medical records have been excluded. The diagnosis of atopic dermatitis was based on the criteria of the United Kingdom Working Party [9].

The data was collected on a standardized form. The variables studied were demographic data (age, sex, environment of residence), clinical data (atopic history and comorbidity, age at the onset of symptoms, degree of severity, existence and type of complications) and biological data (serum total-IgE level). The degree of severity was appreciated by the SCORAD index [10]. The AD was classified as mild for a score of less than 15, as moderate for a score between 15-40 and as severe for a score above 40.

The data was processed using Epi Info7® software. Qualitative variables were expressed in numbers and percentages. Quantitative variables were expressed as mean and standard deviation (SD). The khi-two test with Fisher correction and Yates correction for small numbers was used for statistical analysis. The p-value was significant when it was less than 0.05.

Discussion

In order to describe the epidemiological and associated characteristics of severe AD, our selection of the study population was focused on children because childhood is the period of onset [11].

The small sample size was one of the limitations of this study. The severity of AD was assessed based on clinical criteria using the SCORAD index, which has been shown to be effective [12]. Indeed, there is currently no biomarker for routine assessment of the severity of AD [2]. However, in clinical studies, the measurement of the serum marker CCL 17 showed a good correlation with the severity of the clinically appreciated disease [2]. The weakness of our medical platform did not make it possible to use this biomarker.

In our study, the frequency of severe AD (33.3%) was higher than that reported by other authors. In Ivory Coast, it accounts for 2.9% of cases of AD of childhood [13]. In Tunisia, the severe AD of childhood corresponds to a hospital frequency of 0.085% [14]. Studies in the USA and United Kingdom have shown prevalence of severe AD 7% and 6% respectively [15].

Secondary infection complicated AD in 76% of our children. These were essentially bacterial. Bacterial infection with Staphylococcus aureus (S. aureus) is commonly described during AD [16, 17]. It can cause bacteremia, endocarditis, septic arthritis, and osteomyelitis [18]. Herpes simplex virus secondary infection (eczema herpeticum) may also occur [16, 17]. It is the most severe infectious complication. It was not observed in our study.

Our study reveals the association between severe AD and infectious complications mainly secondary bacterial infection. The microbiota is the set of microorganisms, saprophytes and pathogens that colonize human organs. It has an anti-inflammatory function and a defense function against infection by pathogenic germs [19, 20]. The microbiota is disrupted during AD [20, 21]. Disturbance is greater in the sites of predilection of lesions such as antecubital and popliteal fossa [21]. Indeed, the dryness and high pH of the skin as well as the deficit in antimicrobial peptides favor the selection of S. aureus within the microbiota [19]. S. aureus is present on the skin of more than 90% of AD patients in both healthy and affected skin [21]. Bacterial colonization exposes to the risk of secondary infection, particularly by S. aureus, which plays a role in inflammatory attacks [2, 19, 21]. The work of Kong, et al showed a correlation between the low diversity of the cutaneous microbiota and the severity of the AD measured by SCORAD objective [22]. The association between the severity of AD and infection is supported by several studies. Huang, et al showed that antibiotic treatments had curative efficacy on AD flares [23]. Hon, et al, evaluating colonization and infection of lesions during AD, reports that S. aureus colonized 31% of samples from the most severely affected lesions [24]. His study reveals a high risk of infection for: a SCORAD greater than 40, intense lesions (erythema, lichenification, excoriations) and in case of excess transepidermic water loss. Nomura's analysis further shows that the density of S. aureus on both regions correlates with the severity of AD [25].

Our work also shows the association between elevated total-IgE serum and the severity of the disease. This finding is the same for Holm Denmark in a cohort study that reveals severe AD was associated with increased blood eosinophil count as well as the existence of a high level of serum total-IgE [26]. IgE plays a minor role in the pathogenesis of AD [27]. However, the work of Tolte [28], showing the association between IgE-specific against Staphylococcus aureus and severe AD of childhood, let us suggest a dependence between bacterial infection and IgE. This suggestion remains to be proven by subsequent works. Routine IgE assay may, however, be necessary to identify potentially severe cases early.

Conclusion

This study reveals the high frequency of severe form of atopic dermatitis in childhood and its infectious complications. It identifies secondary bacterial infection and elevated total-IgE serum as factors associated with the severity of the disease.