Conceptions of Clinical Phenotypes

In this video, Jeff Yu, MD, discusses how to break down the concept of phenotypes for patients with AD, including its variations in clinical or research settings.

Dr Yu is a board-certified dermatologist and fellowship trained pediatric dermatologist practicing at Massachusetts General Hospital in Boston, MA. He specializes in allergic contact dermatitis and occupational dermatitis in adults and children.

Transcript:

How does phenotyping of AD vary in clinical vs research settings?

There are different ways of thinking about atopic dermatitis when it comes to phenotype. We can either phenotype patients with atopic dermatitis based on objective measures or based on subjective measures. In the clinical setting, at least, there is some degree of objectivity where you take a look and see what percent body surface area of atopic dermatitis do they have? There are various scales that we can probably use quickly in clinic just to get a quick gauge, but largely we depend a lot on the patient or their caregiver telling us how much does AD really bother you?

Versus in the research setting, however, I think that's where objective measures probably play a slightly larger role because we're talking about publishing these studies or trying to see if there are objective scales that can be done. So in the research setting, people are much more likely to use things like the eczema area severity index, the SCORAD, different types of scoring mechanisms for atopic dermatitis. However, the problem here is that a lot of these scales were developed based on white skin and they may not fully take into account the severity of eczema in patients with darker skin.

What are we learning about AD phenotypes that could inform earlier diagnoses or allow for tailored treatment options?

We understand that atopic dermatitis is probably largely driven by a specific arm of our immune system called the TH2 part of our immune system. However, we know that this is likely not the only mediator. We know this, not only through clinical studies, but also through treatment. So one of the more recent treatments that is available for atopic dermatitis targets the TH2 arm of the immune system, but only about three quarters or less than three quarters of the patients see significant improvement. That must mean that about a quarter of these patients or more have probably AD that is not just mediated by one arm in the immune system, but probably more than that. So I think that understanding that there are other molecules at play could open the door for other targeted treatments that may be effective in those special subtypes of people.

Early treatment with atopic dermatitis with topical medications in some studies have really shown that maybe we can decrease the likelihood of them developing food allergies later on, but we don't really know that yet. That was only through a retrospective study and they haven't been able to do a randomized control studies, but I think that's in the works. But we do know that early intervention for kids that may not have AD such as aggressive skin moisturizing, doesn't actually decrease the prevalence of atopic dermatitis when those kids hit about one year of age. So we're not really sure if early interventions such as probiotics, moisturizing, doing certain things to them can prevent the development of AD. I think that is still largely in the works.

Are there any clinical phenotypes of AD that have difficult-to-discern causes or that can mimic/coexist with other dermatologic conditions?

One of the most challenging things that we see is chronic hand dermatitis. So chronic hand dermatitis, some people even characterize as a completely separate entity, because there are various causes. One of which could be atopic dermatitis, but for a lot of people, hands are the way that they're able to put food on the table, the way they're able to interact with their environment, the way that they're able to carry out a fulfilling career as well as a life at home. So I think management of hand eczema is one of the most important things that we deal with because we try to get people back to work. We try to get people not to change their careers, yet at the same time, delivering them a safe and effective therapy. So I think hand eczema clinically is one of the more challenging ones to treat.

However, sometimes it might be difficult to discern AD other diagnoses as well. One of the main questions is, is this eczema or is it psoriasis? While some treatments overlap between the two, but a lot of the more targeted treatments that we have available nowadays, namely the biologics, they're very different because something that treats psoriasis is probably not going to treat atopic dermatitis. So I think making that difference is important, but depending on your race, for example, Asians, again, some of the AD can really look like psoriasis, making it difficult to diagnose clinically.

The other one that I specialize a lot in is something called contact dermatitis. Now contact dermatitis type of eczema that people get because of what they come in contact with. So we're thinking about metals. We're thinking about fragrances. We're thinking about surfactants. We're thinking about preservatives that are in your daily products. A lot of times contact dermatitis can either coexist with atopic dermatitis, meaning that the patient has both or it could look a lot like atopic dermatitis making the cause of their eczema largely undiagnosed until they actually see somebody who thinks about it and then diagnose them with contact dermatitis, avoids the allergen and then they can get better. So I think there are various mimickers of atopic dermatitis that we need to consider, especially when we're seeing these patients.

How can dermatologists break down the concept of phenotype for patients with AD to promote an open discourse about care options?

Atopic dermatitis, I think, is important for patients to understand that it's a heterogeneous disease. It can look different, it can present differently and everybody has a different time course as well. A lot of parents, especially of younger children, ask me how long is my kid going to have this? I think that's one of the hardest questions because nobody wants to see that their child has a itchy skin condition, and also they don't want to hear he or she may have this for the rest of their life. That's a bit difficult.

Traditionally, we used to tell people depending on the severity of your child's dermatitis or eczema, there's a good chance that they may grow out of it as they go through childhood, go through adolescence and become young adults. We know that a lot more cases of eczema in children do persist into adults than initially believe. We also know that adults can potentially develop eczema as well at a later age. That looks a little bit different than pediatric eczema. So I think it's important for my patients to understand that. That there's nothing that they did that gave them eczema. It's no one's fault or it is not the cat, the dog, it is not something that they're eating, but eczema can present in a variety of different ways. Sometimes it comes on early, such as under the age of two. Sometimes it comes on a little bit later in children and it can look different. Depending on the clinical features of their eczema, depending on the clinical severity of their eczema, we can treat it and we can certainly tailor that treatment to them, to the best of our ability.

But I think it's also important for patients to understand that they can help us with diagnosing and treating their eczema as well. I think patient reported outcomes are extremely important. Sometimes we kind of sit in a dark box where we are giving out treatments, and if we're not hearing back from patients about I like the way this feels, I think this one works better for me. I think that these interventions work better and such, I think having that feedback can be very helpful in terms of helping us tailor our treatments to what's the best treatments that the patient needs, but also help us kind of develop new treatment methodology, treatment ideas, as well as gathering patient feedback, to know how are they doing? Because at the end of the day, that's probably the most important part.