Dr Pedro Mendes Bastos on AD differences between children and adults

Dr Mendes Bastos addressed the heterogeneity of atopic dermatitis patients, causes, and therapy options, and the ongoing research to address them.

In this esanum interview at the EADV 2023, Dr Pedro Mendes Bastos addressed the differences between paediatric and adult AD patients, and explained the exciting new research that is unfolding as of 2023 on the heterogeneity of cases, causes, and therapy options needed. Dr Mendes Bastos explained his work to greater detail in the presentation “Differences in AD of children compared to adults” during the EADV session “Atopic Dermatitis” on Thursday, 12 October 2023.

About Dr Pedro Mendes Bastos: Dr Mendes Bastos is a dermatology physician based at the CDLisboa (Centro de Dermatologia de Lisboa, Portugal). He is a clinical investigator and consultant on dermatology and venereology at the Hospital CUF Descobertas, Portugal. Since May 2023, he was elected as a Board Member for Portugal to the EADV Board of Representatives.

esanum interview at the EADV Congress 2023 in Berlin

esanum: What are the clinical differences in the manifestation and course of atopic dermatitis in children, as compared to adults?

Dr Mendes Bastos: We all are dermatologists, so knowing the differences between clinical manifestations in children and in adults is crucial for proper diagnoses and therapeutic interventions. Atopic dermatitis’ clinical manifestations obey to an age pattern in terms of localization of eczema. If you consider young babies, you will see that the dermatitis is localized mainly on extensor surfaces, on the trunk and on the face. 

In the case of children, you will see the typical flexural involvement, like in the flexural surface of the arms, behind the knees, and the neck. As you grow older, atopic dermatitis tends to look more heterogeneous from a clinical point of view. For adults, every pattern is possible. You can have a pattern similar to childhood with predominant flexural involvement. You can have erythroderma, or a specific eyelid dermatitis pattern, or hand dermatitis pattern. So, in terms of clinical manifestations, as a clinician, you know what to expect, but you should also expect some heterogeneity, particularly in adult patients, because the clinical presentation can trick you and differential diagnosis should be considered both in the paediatric patient with AD as in the adult patient with AD.

esanum: Atopic dermatitis does not always occur in childhood. What are the causes of adult-onset atopic dermatitis?

Dr Mendes Bastos: This is a very interesting topic because for a long time, we believed that atopic dermatitis was a disease that predominantly affected paediatric patients. And we know now that this is absolutely not true. We are increasingly seeing more and more adult patients with AD, and we must consider that not every patient's trajectory is the same. We are seeing adult patients with AD that unfortunately have had AD for their whole lives, since they were babies, and we are also seeing other patterns of adult AD. For example, patients who experienced AD in their young years and then had a long period of remission. And suddenly, AD appeared again in adulthood and sometimes in a more serious form than what they had experienced as children. 

This is very intriguing because we have been attributing atopic dermatitis predisposition mainly to genetics. But you cannot explain if the genetics are the same throughout your lifetime. Why is adult atopic dermatitis appearing? This is not an easy question because we don't know for sure what's happening. But there are some interesting data from very studies published in 2023, that point to differences between paediatric-onset AD and adult-onset AD.

Based on this, it appears that more important than the actual age of the patient you're seeing in the clinic, is the age of onset. Some studies have focused on this, and we are starting to gain some insight regarding this topic. If you had paediatric-onset AD, it's more likely that you have experienced atopic stigmata, it's more likely that you suffered from food allergies, and it's more likely that you have other atopic comorbidities.

On the other hand, if you experienced adult-onset AD, the most interesting theories are mainly linked to lifestyle. Some studies say that it's more likely to have adult-onset AD if you smoke or if you don't practice sports, or if you don't have a strong academic background. And this is something very controversial because we don't know for sure. These are very recent results from epidemiological studies that have been published very recently. This dichotomic hypothesis of genetics and lifestyle is a theory that probably needs further clarifications in the near future regarding adult-onset AD and paediatric-onset AD.

esanum: There is a dichotomy between paediatric-onset and adult-onset AD. But what would be the term for those patients that once they had paediatric-onset AD and remission, but then had adult-onset? Are those adult cases differentiated?

Dr Mendes Bastos: That's a very good question. We don't have data for that. We don't know if those patients should be considered adults-onset or paediatric-onset cases. These are very new concepts. For the first time in 2023, we had studies published on this topic. This is really a hot topic right now. The question is important, but we don't know for sure right now. We need further studies.

esanum: Do risk factors for the development of atopic dermatitis differ between childhood and adulthood?

Dr Mendes Bastos: This concept of risk factor is a very interesting concept for many diseases. We don't know for sure how we should apply them to atopic dermatitis. I mentioned earlier that one epidemiological study showed that probably smoking tobacco may be linked to a higher risk of adult-onset atopic dermatitis. But we don't know that for sure. This was just one study. I think that what is the most interesting aspect of differentiating adult-onset from paediatric-onset is looking at the path of physiology. We know that atopic dermatitis is a very heterogeneous disease from a clinical perspective, but also from a path of physiological perspective.

Some evidence is adding up suggesting that we should probably be facing paediatric-onset AD as a “purer” type-two predominant disease, whereas adult-onset AD may be a disease where obviously Th2 immune dysfunction is present. But you will also find some Th1 dysfunction in a more prevalent way than one should expect earlier. The main point here may be for example, that using specific type-two biologics for paediatric-onset AD may be more interesting than using specific type-two biologics for adults onset AD. This because in the latter you can expect more heterogeneity from a path of physiology point of view and different immune or activated immune pathways other than the type-two immune pathway that characterizes AD. This is very important point because it can be decisive for therapeutic choices and personalized medicine.

esanum: At present there are studies looking into genetics and epigenetics as a cause of diseases. Do you perceive a clear distinction in the research separating these two areas of study or are there hybrid studies dealing with the two at the moment?

Dr Mendes Bastos: This is a very interesting point right now, and yet it is very difficult to evaluate these factors individually because we really are at a stage where we don't know what to look for exactly. So, this is under construction. We are in a very early phase and it's very exciting to see these developments. I think that to achieve personalised medicine and patient-centred therapeutic approaches, we should be focusing on endophenotypes and trying to organise patients in a clearer way that we for sure are not aware of yet.

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