THE 101
- Psoriasis is a common skin condition affecting patients of all skin types.
- In the United States, the estimated prevalence is 3.0% (~7.5 million people) based on a recent popular cross-sectional study using 2011-2014 National Health and Nutrition Examination Survey (NHANES) data with sampling from general, noninstitutionalized United States civilian population in the adult population, with highest in white individuals at 3.6%, followed by non-Hispanic including multiracial at 3.1%, Asians at 2.5%, Hispanics at 1.9% and Blacks at 1.5%.2
- In other parts of the world, the prevalence of psoriasis varies, with the recent rising prevalence reported in some countries due to possibly an increased recognition of psoriasis or increased life span among psoriasis patients. From currently available data, in Africa, the prevalence of psoriasis is about 1.9-3.5% in Eastern Africa, 0.025%-0.9% in Western Africa, 0.14% in East Asia, 0.51% in Southeast Asia, 1.99% in Australasia, 1.92% in Western Europe, 1.83% in Central Europe, 1.3-4.2% in Mexico and Central/South America, 1.10% in southern Latin America.3,4,6,7,9,11,12
- Likely, the prevalence of psoriasis in patients of skin of color may be underestimated due to certain factors, such as non-white individuals being less likely to utilize healthcare and having increased barriers to care.8
Genetic Variations in Psoriasis Susceptibility Among Ethnic Groups
As the prevalence of psoriasis varies worldwide, genetic and environmental factors contributing to the pathogenesis of psoriasis vary between ethnic groups. HLA-Cw*06, the first gene shown to be associated with psoriasis susceptibility, varies among ethnic groups. In psoriasis patients, HLA-Cw*06 is found in 8-26% of Japanese, 76.1% of Korean, 15% of Thai, 6-17% of Taiwanese, 15-19% of Chinese, 34-53% of Indian, 5.7-33% of black, and 46-67% of Caucasian individuals.8 Other psoriasis genes may also explain the difference in psoriasis patterns worldwide, including HLA-B*46 and HLA-Cw*01 are more often found in Asians, HLA-A*02:07 in Chinese, and HLA-B*07 in white individuals.8 Mutations in the IL-36R have been implicated in generalized pustular psoriasis in Japanese and European patients.8 Several genetic polymorphisms encoding components of the Th17-axis, skin barrier function, and pathways within the innate and adaptive immune systems may also play roles in developing psoriasis within non-white populations.
Challenges in Diagnosing Psoriasis in Individuals with Darker Skin
In addition to the genetic changes affecting those of different ethnic backgrounds, psoriasis may be challenging to diagnose in darker-skinned individuals. The classic presentation of the most common type of psoriasis, chronic plaque psoriasis, often presents as sharply demarcated erythematous plaques with silvery micaceous scales. The photos in medical textbooks often reflect a light-skinned individual with this clinical presentation. However, in darker-skinned individuals, erythema may not be as evident, and often patients may present with more hyperpigmented or violaceous plaques, thicker scales, and a more widespread distribution of psoriasis involvement.1 Furthermore, in resolving psoriasis, the post-inflammatory hypo- and hyper-pigmentation may make it challenging to identify which skin areas have active versus non-active psoriasis. The discoloration and scars resulting from psoriasis in darker skin tones may take months to years to fade and contribute to a decreased quality of life for these individuals.
Incorporating Skin of Color in Dermatology Education and Resources
For learners new to the field of dermatology, the current resources that are readily available and accessible may not be adequate for education on psoriasis patients of skin of color. As difficult as it is to diagnose psoriasis in patients with darker skin, distinguishing between psoriasis mimickers may be even more challenging. For example, psoriasis, pityriasis rosea, pityriasis rubra pilaris, and cutaneous T cell lymphoma all fall under the papulosquamous eruptions but remain difficult to identify in darker-skinned individuals.5 One way an early learner can understand the subtleties between different dermatitides is by comparing photographs of common skin conditions in textbooks. The distinguishing features between these conditions are often taught by repeating numerous clinical presentations in textbooks and kodachromes. However, our current textbooks may have limited photos of patients with different skin colors. Fortunately, the modern learner can now access online visual resources beyond classic textbooks. A proposal to consider creating a pipeline for all physicians and physician extenders to incorporate skin of color into teaching slide decks and conferences from medical school to beyond residency at continued medical education events will encourage clinical competency in diagnosing psoriasis and its mimickers in patients of all skin types.
Impact of Psoriasis on Quality of Life in Non-White Individuals
Given the difficulty in diagnosis and often increased severity at clinical presentation, quality of life is affected. It usually is worse in non-white individuals with psoriasis compared to white individuals, even when controlling for disease severity.8 Factors contributing to lower scores in quality of life measures in non-white individuals may include post-inflammatory sequelae, cultural variations in perception of skin disorders, social stigma, emotional support, socioeconomic status, employment status, and educational level.8 Additionally, the tools used to measure the quality of life in patients of diverse ethnic groups may not be adequate for each group. Patients with the same health-related quality of life impairments respond differently to questionnaires and survey items depending on their country of origin. This suggests that better questionnaires may be developed to represent all ethnicities.
Advancing Treatment Approaches for Psoriasis in Diverse Ethnic Populations
Treatment of psoriasis is based on disease severity which often considers clinical presentation, quality of life measures, and individual patient factors. Current therapies for psoriasis, including topicals, oral agents, injectable systemics, and light therapy, are safe and effective for all ethnic groups.13,14 Some adjustments may need to be made for certain ethnic groups, such as hair practices should be taken into consideration, or higher doses may be necessary for light therapy in higher skin phototypes.1,10 However, most clinical trials for psoriasis treatments have been performed in white individuals. A systematic review investigating the diversity of dermatology clinical trials discovered that psoriasis studies had 84.3% of white participants.15 More research is underway on treatment options for patients of diverse ethnic backgrounds in clinical trials. Hopefully, this will allow physicians to apply clinical data to patients of different ethnicities and guide more personalized, optimized, and tailored treatment for all skin types.
References
- Common Dermatologic Disorders in Skin of Color: A Comparative Practice Survey. Alexis AF, Sergay AB, Taylor SC. Cutis. 2007;80(5):387–94.
- Psoriasis Prevalence in Adults in the United States. Armstrong AW, Mehta MD, Schupp CW, Gondo GC, Bell SJ, Griffiths CEM. JAMA Dermatol. 2021;157(8):940-946.
- A Study of the Spectrum of Skin Disease Occurring in a Black Population in South-east London. Child FJ, Fuller LC, Higgins EM, Du Vivier AW. Br J Dermatol. 1999;141(3):512–7.
- Incidence and Prevalence of Psoriasis in Multiethnic Johor Bahru, Malaysia: A Population-based Cohort Study Using Electronic Health Data Routinely Captured in the Teleprimary Care (TPC®) Clinical Information System From 2010 to 2020: Classification: Epidemiology. Choon SE, Wright AK, Griffiths CEM, Tey KE, Wong KW, Lee YW, Suvelayutnan U, Mariapun J, Ashcroft DM; Global Psoriasis Atlas. Br J Dermatol. 2022 Nov;187(5):713-721.
- Top Dermatologic Conditions in Patients of Color: An Analysis of Nationally Representative Data. Davis SA, Narahari S, Feldman SR, Huang W, Pichardo-Geisinger RO, McMichael AJ. J Drugs Dermatol. 2012;11(4):466–73.
- Skin Diseases in Ghana and the UK. Doe PT, Asiedu A, Acheampong JW, Rowland Payne CM. Int J Dermatol. 2001;40(5):323-326.
- About Global Psoriasis Atlas. Global Psoriasis Atlas. Accessed April 9, 2023. https://www. globalpsoriasisatlas.org/
- Psoriasis in Skin of Color: Insights into the Epidemiology, Clinical Presentation, Genetics, Quality-of-Life Impact, and Treatment of Psoriasis in Non-White Racial/Ethnic Groups. Kaufman B, Alexis A. Am J Clin Dermatol (2018) 19:405–423.
- The Variable Incidence of Psoriasis in Sub-Saharan Africa. Leder RO, Farber EM. Int J Dermatol. 1997 Dec;36(12):911-9.
- Issues in Dermatologic Health Care Delivery in Minority Populations. McMichael AJ, Jackson S. Dermatol Clin. 2000;18(2): 229–33, viii.
- Prevalence of Skin Diseases in Ibadan, Nigeria. Ogunbiyi AO, Daramola OO, Alese OO. Int J Dermatol. 2004;43(1):31-36.
- National, Regional, and Worldwide Epidemiology of Psoriasis: Systematic Analysis and Modelling Study. Parisi R, Iskandar IYK, Kontopantelis E, Augustin M, Griffiths CEM, Ashcroft DM; Global Psoriasis Atlas. BMJ. 2020 May 28;369:m1590. doi: 10.1136/bmj.m1590. PMID: 32467098; PMCID: PMC7254147.
- A Retrospective Study to Investigate Racial and Ethnic Variations in the Treatment of Psoriasis with Etanercept. Shah SK, Arthur A, Yang YC, Stevens S, Alexis AF. J Drugs Dermatol. 2011;10(8):866–72.
- Efficacy and Safety of Secukinumab in Taiwanese Patients with Moderate to Severe Plaque Psoriasis: Subanalysis from ERASURE Phase III Study. Wu NL, Hsu CJ, Sun FJ, Tsai TF. J Dermatol. 2017 Oct;44(10):1129-1137. doi: 10.1111/1346-8138.13900. Epub 2017 May 11. PMID: 28493369.
- Diversity in Dermatology Clinical Trials: A Systematic Review. Charrow A, Xia FD, Joyce C, Mostaghimi A. JAMA Dermatol. 2017 Feb 1;153(2): 193-198. doi: 10.1001/jamadermatol.2016.4129.
