Background: The horizontal section of a scalp specimen offers an advantage over a vertical section by providing quantitative information. The reference data for hair counts in Asians, including Thais, are inconclusive. We aimed to determine the normal values of hair counts in scalp biopsy specimens in the Thai population.
Methods: A 4-mm punch biopsy was performed at the occipital area of the scalp from subjects presenting with clinically normal hair and scalp appearance. All specimens were horizontally sectioned and observed to assess the number of follicular units and hair follicles, type of hairs, and phase of the hair cycle. The results were further compared between sexes and with the pre-existing data from previous studies.
Results: Ninety specimens were collected from 90 subjects. The average number of total hairs, terminal hairs, vellus hairs, and follicular units per 4-mm punch scalp skin were 20.5 ± 5.2, 18.2 ± 4.1, 2 (range 0-7), and 9.1 ± 1.6, respectively. The mean ratio of terminal to vellus hair was 8.9:1 and of anagen to telogen hair was 91.9:7.9. There were no gender differences in any of the parameters and no correlations with changing age. Compared to other Asian populations, Thais and Taiwanese showed intermediate values between Iranians and Koreans; when compared to other ethnic groups, hair density in Asians showed lower than Caucasians and Hispanics but was comparable to Africans.
Conclusion: This study established reference values of scalp horizontal sections in the Thai population; this will be helpful for clinicians and researchers to evaluate hair disorders.
© 2020 the International Society of Dermatology.