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.
"As diversity increases in the U.S., understanding these differences becomes important," 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.
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), Dr. Sergay said during a presentation at an international symposium sponsored by L'Oreal Institute for Ethnic Hair and Skin Research. "The survey highlights the variability in skin disorders for which individuals of different racial/ethnic groups present to a dermatologist."
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).
Dyschromia and alopecia made the top 5 list for black patients but did not appear among the top 10 diagnoses for white patients, Dr. Sergay commented.
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. Postinflammatory hyperpigmentation can also result from pseudofolliculitis barbae, which is more common among black patients because of structural differences in the hair follicle and shaft compared with white patients.
Fewer elastic fibers in black skin to anchor hair follicles to dermis might partially explain the higher incidence of alopecia among black patients (Dermatol. Clin. 1988;6:271-81). Chemical and physical hair care practices may also contribute. Other possible explanations are the significantly lower total hair density and number of hair follicles among black patients, compared with white patients (Dermatol. Clin. 2003;21:595-600; Arch. Dermatol. 1999;135:656-8).
Racial variations in skin physiology may lead to differences in eczema prevalence, Dr. Sergay said. Black skin, for example, typically features a greater number of stratum corneum layers. "There is no consensus, however, about the propensity to develop eczema and race or ethnicity."
The single-center source of information is a limitation of the study, as well as potential selection bias from participating physicians, Dr. Sergay said. In addition, categorization of patient ethnicity by a physician or assistant is less reliable than self-reporting.
Melasma is one of the dyschromia diagnoses. Dyschromia and acne accounted for almost half of all black patient visits.
Lower total hair density and number of hair follicles might explain the higher incidence of alopecia in black patients. Photos courtesy Dr. Pearl E. Grimes