The visual appearance of psoriasis can be quite different in skin types V and VI, presenting challenges to diagnosis, said New York dermatologist Dr. Andrew F. Alexis. Cultural practices and quality-of-life issues also require a different therapeutic approach in this population, he said.
Dr. Alexis is the chair of the Department of Dermatology and the director of Skin of Color Center at Mount Sinai St. Luke’s and Mount Sinai West Hospitals, and an associate professor at the Icahn School of Medicine at Mount Sinai. He spoke about psoriasis in individuals with darkly-pigmented skin during the second annual Skin Spectrum Summit in Montreal on May 13, 2017.
While past epidemiological studies have reported psoriasis incidence rates as low as 0.22% among individuals with African ancestry compared to rates above 1% in Caucasians, more recent studies have found incidence rates are much closer between the two groups, said Dr. Alexis.
“A recent study found a prevalence rate of 1.9 per cent in African-Americans—considerably higher than previous reports, and 1.3 per cent of African-Americans in another population study over 27,000 adults in the U.S. So clearly not a rare disease. But probably under-detected,” he said.
Part of the difficulty of detecting psoriasis in individuals with very dark skin—Fitzpatrick skin types V and VI—is that it is much harder to clinically diagnose.
“Once we get into the darker phenotypes, the erythema may not look like erythema,” said Dr. Alexis. “It may look more purplish-brown and dark.”
“Sometimes you do not notice any erythema at all. You may just see grey, and the clue here is the quality of the scale, the sharp demarcation of the plaques, and the anatomic areas of involvement help to clinch the diagnosis of psoriasis.”
In many cases a dermatologist will find evidence of psoriasis from different clues, he said, such as pitting of the nails, the appearance of the scalp, behind the ears, and the sacral area. “But in many cases you do have to rely on biopsy. Much more so in this population than in others,” Dr. Alexis said.
Treatment in dark skinned individuals
Once a diagnosis has been made, treating psoriasis can have unique challenges in this population as well, he said.
Psoriasis appears to have a greater impact on quality of life in non-white individuals, said Dr. Alexis. “In a survey from the National Psoriasis Foundation, 72 per cent of African Americans with psoriasis said it interfered with their capacity to enjoy life. That compared to 54 per cent of Caucasians who answered that question the same way.”
Part of that difference may be due to the vulnerability of dark skin to post-inflammatory pigment changes. Dr. Alexis presented a case in which a psoriasis patient treated with adalimumab achieved PASI-75 with regards to redness, scaling and elevation after 12 weeks of treatment. However, the patient was convinced that the medicine was not working at all because the pigmentary changes on her legs remained severe enough that she felt unable to wear clothes that exposed her legs.
“So the timeline to treatment success in our practice is longer when treating darker skin. And it is important to emphasize what the realistic expectations are for clearance of not just the psoriasis but also the pigmentary sequelae. [We need to] make sure the patients are on board with the plan, remain compliant with our therapy, and do not lose hope by seeing the pigment change persist much longer than the psoriasis itself,” said Dr. Alexis.
Treating scalp psoriasis in patients of African ancestry can also be challenging, said Dr. Alexis, both because of differences in hair structure and cultural differences in hair care practice.
Because of the thinner, dryer, and more fragile hair shaft in this population, as well as the use of hair straightening techniques and labour-intensive hair styles, it is common for individuals of African background to only wash their hair once a week on average. Therefore it is impractical to prescribe daily use of a medicated shampoo, said Dr. Alexis. Instead, he recommends instructing patients to use the medicated shampoo when they would normally wash their hair, to use their regular conditioner, and to apply fluocinolone acetonide the day before they shampoo to help loosen scale. As well, he suggests they apply a potent topical steroid—either clobetasol or fluocinonide—either daily or three times a week for maintenance in a vehicle that is acceptable to that patient’s hair care regimen.
More information about the Skin Spectrum Summit can be found at www.skinspectrum.ca. Registration is still open for the Vancouver Skin Spectrum on May 27.