Structural differences in skin phototypes
Variations in melanosome size and density, collagen, fibroblasts, and other features drive variations in dyspigmentation and scarring (1,400 words, 7 minutes).
Differences in the structure and composition of different skin types drive variations in their prevalence and susceptibility to dermatologic conditions.
This message was part of a presentation by Dr. Archana Kakadekar at the 3rd annual Indigenous Skin Spectrum Summit. Dr. Kakadekar is a dermatopathology fellow in Halifax.
In Brown and Black skin, melanosomes have increased size and density, there are smaller collagen bundles, a compact stratum corneum, larger dermal fibroblasts, fewer ceramides, and larger granules in mast cells, which function to release histamine, said Dr. Kakadekar.
“These differences in ceramides and histamine production are important factors in why patients with phototypes III to VI may present with increased dryness and pruritis,” she said. She also noted that East Asian skin tends to have a thinner stratum corneum, increased serum lipid levels and a weaker skin barrier.
Dr. Kakadekar said the increased density and size of melanosomes in phototypes III and higher contribute to the prevalence of post-inflammatory hyperpigmentation. The body reacts to endogenous or exogenous trauma “by stimulating melanocytes to produce more melanin as a protective mechanism in the dermis and epidermis. This is called pigment incontinence and can lead to deeper pigmentation.”
Keloids are another cutaneous condition seen in richly pigmented skin at 10 to 15 times the rate seen in lighter phototypes, said Dr. Kakadekar. “This is thought to be related to the increased number of dermal fibroblasts, which react to stimulus on a cellular level. That causes them to produce far more collagen in response to an exogenous trauma.”
Bottom line: Fundamental differences in the cellular and extracellular structure of the skin between phototypes contribute to variations in the prevalence and severity of dermatologic conditions. Understanding these differences can support a physician’s management of dyspigmentation and scarring risk.
From the literature on dermatology in skin of colour
Dexamethasone mesotherapy: An alternative for keloid treatment in Hispanic skin
This is a case report of a 32-year-old man with Fitzpatrick skin phototype VI and a six-month history of a keloid on the dorsum of his right hand that caused functional and cosmetic morbidity.
The authors note that intralesional steroid injection is recommended as a first-line treatment for keloids, even though the outcomes are often suboptimal. They write that in keloids, vascular density is higher in the marginal area at subepidermal level due to the elevated expression of vascular endothelial growth factor.
Mesotherapy is a safe and easy technique used in cosmetic medicine, the authors note, which allows for a slower diffusion of dexamethasone and prolongs its pharmacological action, reducing the risk of local side effects.
In this case, the authors performed an intralesional injection of dexamethasone using a mesotherapy technique. This approach led to a significant shrinking of the patient’s keloid and complete recovery of range of motion after two sessions, with no regrowth at the one-year follow-up.
“This technique has the potential to be standardized, but its main drawback is the need for proper sedation. Randomized clinical trials are required to further evaluate the clinical efficacy of dexamethasone mesotherapy,” they write.
A role for vitamin D and the vitamin D receptor in keloid disorder
The authors of this review article note that while several distinct genetic loci have been associated with keloid formation in different populations, no single causative gene has been identified, and the molecular mechanisms guiding keloid development are incompletely understood.
The basis for increased keloid risk in skin of colour is not yet known.
They note that the elevated risk of vitamin D deficiency among individuals with dark skin has led to an increased interest in the role of vitamin D in keloid pathology among the keloid research community.
This review examines the evidence supporting the role of vitamin D and the vitamin D receptor in keloid pathology, including studies that found lower serum vitamin D levels in patients with keloids and reduced expression of the vitamin D receptor in keloid lesions compared with uninjured skin.
Successful treatment of rare adverse event after radiofrequency microneedle on Fitzpatrick skin type IV: a case report
The authors of this paper note that tram-track scarring, also known as uniform papular eruptions, is a rarely-reported but difficult-to-manage adverse event that can occur after radiofrequency microneedle (RFM) treatment.
They report a case of a 27-year-old woman with Fitzpatrick skin type IV and a three-year history of acne vulgaris. The patient had been undergoing treatment for acne vulgaris for the past two years but complained about some acne scars and also expressed a desire for firmer and glowing face skin.
To address these issues, the patient underwent RFM, after which they were instructed to apply gentamycin cream 0.1% for the next three days, avoid excessive sun exposure, use sunscreen with an SPF of 30, and follow up via teledermatology one week after treatment.
One month after the first session of treatment, the patient experienced multiple uniform skin-coloured papules with a needle-tip pattern on their forehead area and hyperpigmented macules with a tram-track pattern that was similar to the needle-tip pattern on their right zygomaticus arch.
These tram track lesions were successfully treated using a combination of 640 nm light-emitting diode therapy and a salicylic acid peel, along with home treatment with azelaic acid and retinoic acid. The lesions completely resolved within six months.
Dermatoses in overweight and obese children and their relationship with insulin and skin colour
This study was conducted to investigate the prevalence of obesity-related dermatoses in obese children and the association between these dermatoses, insulin resistance, and skin colour.
Researchers included 70 girls and 41 boys (mean age 12.37±3.14 years) who had been followed up and treated in the outpatient clinics in the study. Investigators performed dermatologic examinations of the participants and checked fasting insulin and glucose levels. A group of 101 healthy children with average weight (59 girls, 42 boys, mean age 12.15±2.43 years) were used as controls.
The five most common dermatoses in the patient group, when compared with the control group, were keratosis pilaris (KP), striae distensae, hyperhidrosis, acanthosis nigricans (AN), and plantar hyperkeratosis. The five dermatoses with the most positive correlation between their formation and insulin resistance were KP, striae distensae, AN, hyperhidrosis, and plantar hyperkeratosis. The investigators found that the darker the skin colour, the higher the probability of AN and KP (Odds Ratio (OR), 0.298; 95% Confidence Interval (CI), 0.106-0.834, p=0.021; OR, 0.306; 95% CI, 0.117-0.796, p=0.015, respectively).
The authors conclude that their findings suggest that many skin morbidities may be prevented by avoiding and treating obesity and insulin resistance early.
At the intersection of skin and society
The Black Physicians’ Association of Ontario held a conference in Toronto on Saturday, May 4, 2024, for family doctors, nurse practitioners, psychiatrists, psychologists, social workers, and other healthcare providers to address barriers Black youth face regarding access to mental health services, reports The Globe and Mail.
“Black youth experience the mental health system very differently than other races,” said Dr. Mojola Omole, president of the association and a general surgeon in Toronto.
“That is in part due to anti-Black racism and implicit biases,” said Dr. Omole, who also works with the Canadian Medical Association Journal on addressing those issues in health care.
Many Black youth have experienced trauma, sometimes stemming from racism or discrimination, which can affect their mental health and the way they express themselves, she said.
“What might seem like apathy is the sign of actually having problems,” Dr. Omole said.
“There’s been a lot of adjustment made from constant PTSD and just active trauma that they don’t necessarily have the same reaction that you would see in others.”
Dr. Omole said that when Black youth speak loudly, it is often falsely perceived as aggression.
The event’s keynote talk, “Laying the Groundwork—What do Black youth bring with them into care encounters?” was presented by Dr. Samra Sahlu, an adult psychiatrist who practices in Saskatoon and Toronto. She is also part of the SAPACCY (Substance Use Program for African Canadian and Caribbean Youth) team at the Centre for Addiction and Mental Health (CAMH) in Toronto and the Mobile Crisis Team supported by the TAIBU Community Health Centre in Scarborough, Ont.
This week
May 12 to 18 is Food Allergy Awareness Week
May 15 is International Vascular Birthmarks Awareness Day
May 19 is Malcolm X Day
Something to think about in the week ahead. . .
—Eknath Easwaran, Indian author and translator (1910-1999)
Next week
In a presentation at the 2023 Indigenous Skin Spectrum Summit, Kristian Blind, RN, discusses barriers to dermatology care in remote Indigenous communities and some available resources.
If you like Skin Spectrum Weekly, why not check out Chronicle’s other publications, podcasts, and portal?
Established in 1995, The Chronicle of Skin & Allergy is a scientific newspaper providing news and information on practical therapeutics and clinical progress in dermatologic medicine. The latest issue features:
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Dr. Afsanah Alavi (Rochester, Minn.) details recent research showing a link between lower limb lymphedema and skin cancer.
Drs. Reetesh Bose (Ottawa), Morvarid Hessami (Toronto), and Marissa Joseph (Toronto) describe the establishment of dermatology clinics specializing in skin colour and the outcomes they are achieving.
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Good article!!