MIAMI — Unique structural and functional differences between the skin of black and white patients might help explain differences in the top five dermatology diagnoses for each ethnicity, according to study data presented at an international symposium sponsored by L'Oreal Institute for Ethnic Hair and Skin Research.
Prior to this study, the most recent survey of cutaneous diseases in black Americans was published more than 2 decades ago (Cutis 1983;32:388–90), said Dr. Amanda B. Sergay, a third-year dermatology resident at St. Luke's-Roosevelt Hospital Center in New York City.
Dr. Sergay and her associates, including principal investigator Dr. Andrew F. Alexis, retrospectively compared the diagnostic codes for 1,074 black and white patient visits treated at the Skin of Color Center at St. Luke's-Roosevelt Hospital Center, New York City, from August 2004 to July 2005. When ethnicity was unclear, the patient's own description was used.
Acne vulgaris was the most common diagnosis in both groups (ICD-9 code 706.1). “The pathophysiology of acne is not thought to differ between races or ethnicities,” she said at the symposium, which was also sponsored by Howard University.
Acne and dyschromia (code 709.09) are so common that they accounted for almost 50% of black patient visits (Cutis, in press: November 2007). Black patients also were commonly diagnosed with contact dermatitis and other eczema, unspecified cause (code 692.9), alopecia (code 704.0), and seborrheic dermatitis (code 690.1).
After acne vulgaris, the most common diagnoses in white patients were a lesion of unspecified behavior (code 238.2), benign neoplasm of the skin of the trunk (code 216.5), contact dermatitis or other eczema, and psoriasis (696.1).
In black patients, dyschromia and alopecia made the top-5 list, but they were not among the top 10 diagnoses for white patients, Dr. Sergay said. The dyschromia diagnoses included postinflammatory hyperpigmentation and melasma.
“Postinflammatory hyperpigmentation is a common sequela of cutaneous injury or irritation in skin of color,” Dr. Sergay said. It can also result from pseudofolliculitis barbae, which is more common in black than in white patients because of structural differences in the hair follicle and shaft.
The higher incidence of alopecia in black patients could be partially explained by the fact that there are fewer elastic fibers in black skin to anchor hair follicles to the dermis (Dermatol. Clin. 1988;6:271–81). Chemical and physical hair care practices may also contribute to alopecia, as could the significantly lower total hair density and number of hair follicles in black patients, compared with whites (Dermatol. Clin. 2003;21:595–600; Arch. Dermatol. 1999;135:656–8).
Racial variations in skin physiology may also lead to differences in eczema prevalence, Dr. Sergay said.
The single-center source of information was a limitation of the study, as was potential selection bias from participating physicians, she said, adding that categorization of patient ethnicity by a physician or assistant is less reliable than self-reporting.
Melasma, a skin pigmentation disorder, manifests as dark spots on the face.
Blacks' skin physiology and hair-care practices make them prone to alopecia. Photos courtesy Dr. Pearl E. Grimes