When it comes to treating atopic dermatitis in non-white racial ethnic groups, there are variations in prevalence, genetic factors and clinical presentation.
Dr. AlexisWhen it comes to treating atopic dermatitis in non-white racial ethnic groups, there are variations in prevalence, genetic factors and clinical presentation.
In addition, delays in treatment and undertreatment can contribute to a higher risk of pigmentary sequelae, including hyperpigmentation and hypopigmentation.
“Fortunately, recently approved therapies show promise in improving outcomes of atopic dermatitis in this patient population,” says Andrew Alexis, M.D., chair of the Department of Dermatology at Mount Sinai St. Luke’s and Mount Sinai West in New York City.
Multiple studies from the United States and the United Kingdom demonstrate that the prevalence of atopic dermatitis is greater in blacks than in whites.
For example, a study published in the Journal of the American Academy of Dermatology in 1995 found that London-born Caribbean children of African ancestry had a 16.3% prevalence rate of atopic dermatitis compared to a rate of 8.7% in London-born white children.
Furthermore, in America, African American children were found to be 1.7 times more likely than their white counterpoints to have a diagnosis of atopic dermatitis, even after adjustment for potential confounding variables, according to a 2011 article in the Journal of Investigative Dermatology.
Another U.S. study, reported in the Archives of Dermatology in 2012, found that blacks, Asians and Pacific Islanders were more likely than whites were to visit physicians for atopic dermatitis.
“In fact, looking at the number of atopic dermatitis visits, blacks had two-fold higher visits per capita than whites, whereas Asians and Pacific Islanders had six-fold higher visits per capita,” Dr. Alexis tells Dermatology Times. “However, this is not due to greater healthcare utilization, as these non-white groups had lower overall utilization for medical and other skin conditions. This speaks to not only the higher prevalence, but the greater burden of atopic dermatitis among various non-white racial ethnic groups.”
Excluding erythema, non-whites were six times more likely to have severe atopic dermatitis than were their white counterparts, according to a study published in the British Journal of Dermatology in 2002.
Moreover, studies have shown differences in the lipid content of the epidermis of different populations. For instance, a key lipid, ceramide, is lower in African Americans than in other groups, according to a study from the Journal of Cosmetic Science in 2010, while ceramide/cholesterol ratios were found to be lower in Africans compared to whites in a study in the British Journal of Dermatology in 2010.
Other studies indicate differences in the genetic risk factors for atopic dermatitis. “Whereas atopic dermatitis patients of European ancestry frequently have filaggrin null gene mutations, the prevalence of this specific gene mutation in African Americans and other groups of African ancestry with dark skin is lower,” says Dr. Alexis, who spoke on atopic dermatitis at the Skin of Color Seminar Series (SOCSS) in New York City in May. “This finding suggests that there may be other genetic factors that are more predisposing in individuals of African ancestry.”
The trend in the typical cytokine profile seen in atopic dermatitis among East Asian patients vs. Caucasians is also different. “East Asians have a higher tendency to have a predominant Th17 and Th22 cytokine profile and a more psoriasiform presentation of atopic dermatitis,” says Dr. Alexis, referencing a 2015 article in the Journal of Allergy and Clinical Immunology.
The erythema associated with atopic dermatitis can be masked by background pigment, “so instead of increased redness, it may look like darkness or hyperchromia or hyperpigmentation instead of classic erythema,” Dr. Alexis says. “Thus, using clues like papulation, lichenification, scaling and excoriation is more reliable in assessing the severity of atopic dermatitis in darker skin.”
Eruptions and hyperpigmentation
Two unique presentations that are seen more commonly in darker skin types are micropapular and follicular eruptions, particularly in individuals of African ancestry. A lichenoid presentation that resembles lichen planus is rarer but has also been described in African Americans.
On the other hand, postinflammatory hyperpigmentation is a significant and common sequelae of atopic dermatitis in darker skin. “In fact, the hyperpigmentation can be almost as burdensome as the rash itself, whereby large areas of the body, including the arms, the legs and the torso, can be covered with hyperpigmented patches that are quite disfiguring,” Dr. Alexis says.
Pigmentary changes may also occur as a result of treatment with topical steroids, leading to hypopigmentation, “which is more pronounced visually in darker skin,” Dr. Alexis says.
For treatment overall of darker skin, “it is particularly important not to undertreat, but to aggressively target the underlying inflammation and to protect the skin barrier,” says Dr. Alexis, who advocates the liberal use of moisturizers, emollients and barrier repair products in conjunction with immunomodulatory therapies.
“With the advent of new therapies that target specific pathways within the pathogenesis of atopic dermatitis, it is likely we will be able to manage these patients more effectively,” Dr. Alexis says.
New treatment options
Two recent notable additions to treatment options for atopic dermatitis are topical crisaborole (Eucrisa, Pfizer), a phosphodiesterase type 4 inhibitor (PDE4), which blocks strategic parts of the pathway leading to the inflammation and barrier dysfunction in atopic dermatitis, and the injectable biologic agent dupilumab (Dupixent, Regeneron), which blocks two critical cytokines (IL-4 and IL-13) implicated in the skin disease.
“Both of these therapies have shown significant efficacy and safety,” says Dr. Alexis, director of the Skin of Color Center at Mount Sinai St. Luke’s and Mount Sinai West.
Studies enrolled a sizable proportion of non-white racial ethnic populations, with the Phase III crisaborole trials comprising approximately 40% non-white patients and the Phase III dupilumab studies involving about 32% non-white patients.
When comparing the safety and efficacy of dupilumab in white patients vs. black patients vs. Asian patients for the Phase III studies, “we found no racial ethnic differences in efficacy or safety for moderate to severe atopic dermatitis,” says Dr. Alexis, who was one of the investigators of the comparison study.
Contact dermatitis is another type of eczema that differs in racial ethnic. For instance, a study published in 2016 in the journal Dermatitis found differences between black and white patients related to the frequency of allergens detected in patch testing.
“Blacks were significantly more likely to have a skin reaction to the chemical paraphenylendiamine [PPD], which is found in black hair dye; bacitracin; and specific rubber accelerators,” says co-author Dr. Alexis. “This is based on data from the North American Contact Dermatitis Group.”
These differences are more likely due to differences in environmental exposures to these agents, rather than to genetic differences, says Dr. Alexis.
Because of varying exposures among different populations, there are unique presentations of contact dermatitis, including reactions to henna dye that is mixed with PPD, and cultural practices. “For example, there is a type of contact dermatitis observed in devout Hindus, who smear an ash-based substance across their forehead called vibhuti,” Dr. Alexis says.
Dr. Alexis believes that the addition of new therapies specifically targeting key inflammatory pathways in the development of atopic dermatitis should “revolutionize” treatment of the skin disorder in all patients, including patients of color.
Disclosures: Dr. Alexis is a consultant to Regeneron and serves on the advisory boards of Anacor, Galderma and La Roche-Posay.