Racial/ethnic data on psoriasis lacking
Estimates of prevalence of the skin condition hampered by small number of studies and lack of balance in skin types (1,450 words, 7 minutes)
There is limited worldwide data on the prevalence of psoriasis broken down by race and ethnicity, which raises doubts about the commonly expressed idea that the disorder is less common in populations with skin of colour.
This view was described during a presentation by Dr. Yvette Miller-Monthrope at the 7th annual Skin Spectrum Summit on Nov. 4.
Dr. Miller-Monthrope is a dermatologist, pathologist, and dermatopathologist and is Assistant Professor of Medicine at the University of Toronto.
“Psoriasis affects about 125 million people worldwide, up to three per cent of the global population, with a higher rate among Caucasians,” said Dr. Miller-Monthrope.
“In Canada, it is thought to affect about a million people, but there is limited data on race and ethnicity. In the U.S., it affects about 3.7 per cent of the population, with Caucasians having the highest prevalence, followed by African Americans, then Hispanics, then other.”
“But we have to ask if it is really true that psoriasis is less prevalent in patients with skin of colour, and I would say probably not,” she said, noting that 81% of countries lack reported information on psoriasis epidemiology. Even in nations where data is reported there are factors that raise questions about its accuracy, she noted.
“In the U.S., we know that non-Caucasian populations are more likely to have undiagnosed psoriasis. Why? This could be because of issues with access to healthcare or decreased healthcare utilization. But it could also be because psoriasis presents differently in patients of colour, and this could lead to incorrect diagnoses,” she said.
Another factor is an under-representation of skin of colour patients in clinical trials across all dermatological conditions, she said. In U.S.-based psoriasis clinical trials, 84.3% of participants are recorded as white, even though nearly 40% of the U.S. population self-identifies as non-white.
Dr. Miller-Monthrope provided some prevalence information on psoriasis from around the world:
In Africa, the rate varies geographically, with rates in East African countries up to 3.3%, while reports from West Africa indicate only 0.05 to 0.3% have psoriasis. Dr. Miller-Monthrope’s own experiences in a dermatology clinic in Botswana in southern Africa suggest high rates of psoriasis in that region as well.
In Asia, rates are thought to be quite low, though potentially varying by region. Dr. Miller-Monthrope described a report that showed Malaysian and Indian children were found to have three to four times more psoriasis diagnoses than Chinese children.
Rates vary extensively in Latin America and the Caribbean. Up to 6% of dermatology consults in Cuba are reported to be for psoriasis. A study in Trinidad and Tobago showed 5.1% of patients had the condition. In Mexico and parts of South America, the rate ranges from 1.3 to 4.2%.
Bottom line: Psoriasis is likely under-diagnosed in people of colour, due to a lack of clinical data and misdiagnosis because of differences in clinical presentation.
From the literature on psoriasis in skin of colour
Psoriasis prevalence in adults in the United States
This population-based, cross-sectional survey used psoriasis prevalence data from the 2011-2014 U.S. National Health and Nutrition Examination Survey (NHANES) and compared it to similar data from the 2003-2004 NHANES.
Looking at data from 12,625 participants, of whom 4,828 were non-Hispanic white individuals, psoriasis prevalence among U.S. adults 20 years or older was 3.0%. Broken down by racial/ethnic groups, the prevalence was highest in white individuals (3.6%), followed by other groups (non-Hispanic, including multiracial, 3.1%, Asian at 2.5%, Hispanic including Mexican American and other Hispanic individuals at 1.9%, and Black at 1.5%. The prevalence of psoriasis was not different based on patients’ marital status, education, income, or medical insurance status.
Overall, these prevalence numbers did not differ significantly from the 2003 values, the authors note.
Dermoscopic characterization of guttate psoriasis, pityriasis rosea, and pityriasis lichenoides chronica in dark skin phototypes: An observational study
This retrospective observational study included 20 histopathologically confirmed cases each of pityriasis rosea (PR), guttate psoriasis (GP), and pityriasis lichenoides chronica (PLC) seen over a period of three years. Cases in the study were all in patients with Fitzpatrick phototypes III, IV, and V.
The investigators found that the most common background colour under dermoscopy in PR (86.7%) and PLC (96.7%) was yellow to yellow-orange. In GP, the most common background colour was dull red to pink (70%). Vessels were visualized in all GP lesions with the most characteristic pattern being regular (93.3%) and dotted vessels (95%). In PR 63.3% of lesions had dotted vessels mostly in a patchy distribution (56.7%). The most prominent scale coloP.R. in PR was yellow-white (88.3%) aG.P. in GP was white-grey (80%). Scale colours varied in PLC with brown being most prominent (53.3%).
Researchers saw hypopigmented areas (13.3%), brown dots and globules (53.3%) and orange-yellow structureless areas (61.7%) only in PLC. The authors conclude that there are specific dermoscopic findings that can differenG.P.ate GP, PR, and PLC and that the known dermoscopic criteriG.P.for GP, PR, and PLC also apply for dark skin prototypes.
Transcriptome analysis reveals intrinsic pro-inflammatory signalling in healthy African American skin
To better understand the underlying mechanisms behind the differences in prevalence and clinical features of inflammatory skin diseases (including psoriasis) in dark skin, researchers compared baseline gene expression in full-thickness skin biopsies from African American and non-Hispanic white individuals.
They identified 570 differentially expressed genes (DEG) in African American skin including immunoglobulins and their receptor; pro-inflammatory genes such as TNFα, IL-32; EDC (epidermal differentiation cluster) and keratin genes. The DEGs were functionally enriched for inflammatory responses, keratinization, cornified envelope formation. When the investigators analyzed 3D human skin equivalents (HSE) made from African American and non-Hispanic white primary keratinocytes they found 360 DEGs, some of which were shared with skin, which were enriched by similar functions. The AA HSE appeared more responsive to TNFα pro-inflammatory effects. Researchers also found a significant overlap between DEGs specific to African Americans in skin and HSE and the molecular signatures of skin in AD and psoriasis patients.
The authors conclude their findings suggest the existence of intrinsic pro-inflammatory circuits in African American keratinocytes and skin that may account for disease disparities. They write that this discovery may help to build a foundation for the development of targeted skin disease prevention.
Association of HOTAIR polymorphisms with susceptibility to psoriasis in a Chinese Han population
The goal of this study was to investigate the association between HOX transcript antisense RNA (HOTAIR) polymorphisms and psoriasis in a Chinese Han population.
Researchers enrolled 269 patients diagnosed with psoriasis and 273 healthy control subjects. From samples from these participants, the investigators genotyped three single nucleotide polymorphisms (SNPs) of HOTAIR: SNP1 (rs12826786), SNP2 (rs1899663), and SNP3 (rs4759314). They found a statistically significant difference in the distribution of the rs4759314 genotype in the control group and case in all of their models except the recessive model. They also found that the rs12826786 SNP was associated with a risk of psoriasis.
The authors conclude that a genomic variant within HOTAIR was associated with a risk of psoriasis in this population, and the clinical value of this study should be further evaluated in the future.
VIDEO: Psoriasis in Patients of Colour
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At the intersection of skin and society
Efforts are underway to expand the IndigeFame’sport Gallery at the British Columbia Sp“rts Hall of Fame into an interactive online experience, as well as to translate the gallery’s content into Indigenous languages. This news cB.C.es via a press release from the government of B.C.
Funded by the province of B.C., the expansion project is being conducted in partnershipprovince’sgenous Pe”p“es, communities and sports organizations.
Completion is expected in spring 2023.
According to the Hall of Fame’s website, the Indigenous Sport Gallery “celebrates the rich history”and many contributions to sport by more than 40 Indigenous athletes, teams, coaches, builders and volunteers in BC, and att“mpts to remedy the fact that Indigenous athletes and teams have not been properly celebrated and honoured over the course of the province’s history.”
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This week
Dec. 10 is international Human Rights Day
Dec. 12 is International Universal Health Coverage Day
Something to think about in the week ahead…
Next week
In our Dec. 13 edition, we cover Dr. Jaggi Rao’s presentation from the 2021 Skin Spectrum Summit, in which he discusses the four types of rosacea and how they present and are treated in skin of colour.