Healthcare disparities exist in all fields of medicine, including dermatology. Despite movements to educate the general public, many myths related to dermatology still exist, such as the belief that those with darker skin tones do not need to protect their skin because they have a minimal risk of developing skin cancer. While it is true that increased amounts of melanin and the mechanisms related to melanosomes in people with skin of color do provide a significant level of photoprotection1, they are still at risk for all the same conditions that affect lighter skin types, though these conditions may present differently and have poorer outcomes.
The purpose of this brief review is to focus on some differences in epidemiology, presentation, access and outcomes in different skin types for five dermatologic conditions: atopic dermatitis, melanoma, hidradenitis suppurativa, melasma, and vitiligo.
Atopic dermatitis (AD) is an increasingly common condition estimated to affect over 30 million children and adults in America of all colors, albeit with significant differences in prevalence, response to treatment, and molecular biology.2,3 In population studies, AD has been found to be more prevalent in African American and Asian/ Pacific Islanders individuals than Caucasians.4,5 This may be explained by increased inflammation due to higher affinity IgE receptors and decreased innate immune markers including Th1 and Th17 found in African Americans when compared to European Americans with the condition.6 As Sanyal and colleagues discuss in their article, differences on the molecular level may begin to explain why African Americans don’t respond to treatment exactly like other groups, and tend to require higher levels of corticosteroids, have a higher risk for hypopigmentation, and are more likely to need higher doses of cyclosporine A and ultraviolet B light. Similar studies examining Asians and Pacific Islander populations found that their immune system has a stronger Th17/Th22 response compared to Caucasians, leading to increased inflammation and more pronounced presentation of AD, especially since it tends to present as a mix of AD and psoriasis in this population.4,7 Notably, the markers Th2, Th22, and IgE are all correlated with increased AD severity, and these are markers that are more common in African American and Asian populations.6
In terms of presentation, African Americans have increased risk for post-inflammatory dyspigmentation, plaques on extensor surfaces instead of traditional flexor surfaces and have scattered distinct plaques; while Asian patients more likely to have scaling and lichenification than Caucasians.4 Another layer of complexity is added when examining the disparities between the healthcare access in populations affected by AD. For example, non-Hispanic blacks had 33% lower odds of keeping follow-up appointments for their AD, and those that did access medical care had more ambulatory visits and filled more prescriptions than non-Hispanic whites.8 These molecular differences amongst populations affected by AD make it crucial to continue increasing diversity in clinical trials in order to obtain personalized, evidence based treatment recommendations for patients with each skin type.
The disparities related to melanoma are quite striking. Although 95% of cases are diagnosed in people with white or light skin9, the remaining 5% of cases in African Americans and Hispanics have poorer prognosis due to diagnosis at more advanced stages and the subtype of melanoma.10 Multiple studies11,12 have found that the 5-year survival rate in African Americans and Hispanics is much lower than that of Caucasians, 72% to 81% versus 90%.12 People of color diagnosed with melanoma tend to have the acral lentiginous subtype, which is more invasive.13 Focusing on Hispanic populations, it has been found that they are about 20% less likely than non-Hispanics to perform skin self-examination.14 Alarmingly, the prevalence of physician skin exams varied by patient language abilities. One study surveyed 4,766 individuals who identified as Hispanic, and found that patients who mostly or only spoke Spanish were almost three times less likely to report ever having had a physician skin examination compared to Hispanic patients who mostly or only spoke English.15 This suggests that increasing the diversity of dermatologists may increase skin cancer detection by making patients feel more comfortable communicating with a provider that speaks their language and knows their cultural practices.16
Hidradenitis Suppurativa (HS) is a chronic inflammatory condition that affects up to 4% of the American population17, and in several studies in the United States has been found to be more common in African American and Hispanic female patients.18,19,20 This may be due to these two populations being more likely to be obese, have metabolic syndrome, and smoke cigarettes, all of which are risk factors for the development of HS.18 In a Dutch population, this disease was found to be associated with lower socioeconomic status.21 Low socioeconomic status makes it difficult for families to buy fresh produce, and their neighborhoods may preclude them from exercising outside for safety reasons, thereby contributing to obesity and metabolic syndrome and ultimately dermatologic conditions such as acanthosis nigricans and HS.
Anatomic and genetic differences also play a role in the differences in HS across ethnic groups. A study in the early 1900s concluded that people of African heritage had three times the amount of apocrine glands as compared to Caucasians, a finding that is striking and prompts further investigation.18,22 Few studies have looked at the genetic differences in patients affected by HS, and no trials to date have examined the efficacy of adalimumab, the gold standard FDA approved medication, across ethnic groups. This is important because African American women have been found to be more likely to fail medical treatment and undergo surgery for this disease.23 Patients that lack access to healthy foods and exercise are at increased risk for metabolic problems, and, ultimately, skin manifestations. It is the role of dermatologist to work alongside primary care providers to encourage lifestyle modifications, in addition to treating and researching the skin condition.
Melasma is a common condition of hyperpigmentation primarily occurring on the face and other sun exposed areas. The national and worldwide prevalence is unknown, however many studies have found that it is more common in populations of Hispanic, African, and Asian/ Pacific Islander descent, and pigmentation disorders overall are within the top 5 most common dermatologic concerns.24,25,26 Melasma is influenced by hormones, and is more likely to arise or worsen in pregnancy and in women taking oral contraceptives.27,28 Beyond encouraging all patients to use appropriate sun protection, treatment response varies by a patient’s skin type. Patients with darker skin are at higher risk for post-inflammatory hyperpigmentation after laser therapy, and further dyspigmentation and keloid formation following deep peel treatments.26 In addition to patients’ concern about appearance, melasma greatly affects every day life, including social interactions, health and financial concerns 29 Patients with melasma have higher rates of anxiety and depression, and are more likely to take antidepressants than those without the condition.24
Finally, the most prominent risk factor for melasma onset and exacerbation is sun exposure. One small cohort study looking at Puerto Rican women found that in all cases, their mandibular melasma was exacerbated by sun exposure and lead to hyperpigmentation on histology.30 This finding suggests that populations closer to the equator, or more tropical conditions tend to have more risk factors for worsening melasma. Mahmoud and colleagues tested this concept and found that both visible light (400-700nm) and long- wavelength UVA1 (340-400nm) caused more prominent pigmentation in volunteers with darker skin (Fitzpatrick IV-VI), than those with skin type II, suggesting that even broader-spectrum sunscreens should be recommended, including those with iron oxide as a tint to help block visible light.31 Sun protection, thus, seems every bit as important for patients with skin of color: in addition to increasing the risk of skin cancer, sun exposure also plays a critical a role in pigmentary disorders.
Whereas melasma represents the overproduction of pigmentation, vitiligo presents as the opposite problem: no pigmentation at all. Vitiligo affects about 1% of the population, incidence does not vary by skin color, and it affects men and women equally.32 The pathogenesis of vitiligo remains controversial, however a common theory supports an autoimmune origin since many patients with vitiligo tend to be diagnosed with autoimmune diseases, especially those involving the thyroid33. These factors add to the burden of disease, which has been studied in patients with vitiligo. A national study by American Academy of Dermatology was completed using 2013 claims data to examine the burden of disease in various skin diseases. The medical costs for vitiligo were calculated at $49 million and lost productivity of $6 million.34 Although this was on the lower end of the spectrum compared to the other skin diseases studied, it still demonstrates the financial burden posed by this disease. Patients with darker skin types tend to fail conservative treatments and are more likely to need phototherapy, which can be more expensive and time consuming.35
That being said, some may argue that the psychosocial burden of vitiligo is even more salient. Across ethnicities, patient vignettes on the effect of this disease show themes of low self-esteem, grief, and humiliation that affect every day life. There is not a consensus on the effect of skin color on psychosocial burden from vitiligo. Several studies demonstrate that patients with darker skin types (Middle Eastern, Caribbean and Indian heritage) perceived greater burden compared to lighter-skinned individuals 36, and another claimed that African Americans experience loss of racial identity37, yet the overall stress associated with vitiligo was the same across ethnic groups in more recent works.38 The burden of disease in vitiligo is significant across every group, and dermatologists need to keep psychosocial factors in mind when treating all patients with vitiligo.
UNITED COLORS OF DERMATOLOGY
There are important differences affecting people of color that need to be addressed and explored. Ideally, dermatologists will unite around their patients by continuing public education on skin exams and skin protection in various languages, and working with primary care colleagues to enhance screening and referrals. Increasing diversity among practicing dermatologists may also help to combat these disparities. While patients may feel more comfortable and increasing diversity in medicine will likely help, until that time, it is important to be aware of these disparities and important differences.
Any dermatologist can become more knowledgeable about these issues by joining the Skin of Color society, whose mission to educate both providers and patients on issues related to the wellbeing of skin of color.39 There is also a need to increase diversity of enrollment in research trials, and make them more representative of the populations most affected by each condition in order to ultimately have evidence-based treatment recommendations for each skin type. In the meantime, we hope to continue to explore these issues, and strive to improve outcomes for all.
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