Not only is atopic dermatitis considerably more prevalent in children than adults (12% versus 7.2%), the prevalence of its particular phenotypes and subtypes can also vary markedly across different age groups. For example, in adults, the condition more frequently presents on the hands or feet.
“The key challenge for adult eczema is we often see less flexural disease and more of those other subsets,” says Jonathan Silverberg, associate professor and director of the Northwestern Medicine Multidisciplinary Eczema Center and of the Contact Dermatitis Clinic at Northwestern Memorial Hospital in Chicago. “Couple that with the fact that the differential diagnoses are much broader, and a couple of entities in the differential diagnoses are more common, and atopic dermatitis becomes a very challenging diagnosis.”
Other conditions, such as contact dermatitis, cutaneous T-cell lymphoma and cutaneous/systemic lupus erythematosus need to be ruled out, and then “atopic dermatitis almost becomes a diagnosis of exclusion,” he says, with the patient meeting the clinical criteria after other conditions have been ruled out.
As atopic dermatitis tends to present differently in adults and children, it is likely that there are also some differences in the underlying pathological disease processes, meaning that different treatment modalities may prove to be more effective in adults than children and vice versa. Currently, it is difficult to compare the efficacy of different treatments in children as adults, because, as treatments are first licensed based on studies in adults, very little data often exist on effectiveness in children, and even less from head-to-head comparative trials.
“Logically, there will be differences as some of these pathways are more relevant in adults than children, that is why there is a real rationale to study children separately from adults and not to make assumptions that a child would respond as an adult would, or vice versa,” he explains.
“In reality there may be a variety of different immune mechanisms implicated and some more relevant in children than adults. These are all very theoretical at this point but they may not be for very long. In the next few years I think we will have some really important data to digest between children and adults across a variety of different immune pathways.”