Quantification of Hair Follicles in the Scalp in Mexican Mestizo Population

Evaluation of Scalp Hair Density and Diameter in the Arab Population: Clinical Office-Based Phototrichogram Analysis

Background

Knowing normal values of scalp hair thickness and density is beneficial for diagnosing hair disorders, monitoring responses to therapy, performing hair transplants, and conducting relevant research. Such normal values have not yet been studied for Arabs.

Objective

To assess the hair density and diameter of the Arab population at different scalp sites using phototrichogram.

Methods

A cross-sectional descriptive study was performed at King Saud University Medical City from December 2021 to August 2022. The study was conducted on Arab adults who were not suffering from any hair disorder. The study was conducted using a questionnaire and clinical examination by phototrichogram.

Results

A total of 120 participants were enrolled in this study. The mean hair density was 147.1± 7.8 hairs/cm2, and the mean hair diameter was 87±4.9 μm. There were significant differences between hair density (P=0.0001) and diameter (P=0.0001) in different regions of the scalp. Females had higher hair density than males at occiput (P=0.038).

Conclusion

Arab hair has a higher thickness and lower density than hair of other ethnicities. This needs to be considered when diagnosing and/or treating hair problems in Arabs.

Variations in genetics, biology, and phenotype of cutaneous disorders in skin of color - Part I: Genetic, biologic, and structural differences in skin of color

Skin of color (SOC) populations include those who identify as Black/African, Hispanic/Latinx, Asian/Pacific Islander, American Indian/Native Alaskan, Indigenous Australian, Middle Eastern, biracial/multiracial, or non-White; this list is far from exhaustive and may vary between and within cultures. Recent genetic and immunological studies have suggested that cutaneous inflammatory disorders (atopic dermatitis, psoriasis, and hidradenitis suppurativa) and malignancies (melanoma, basal cell carcinoma, and cutaneous T-cell lymphoma) may have variations in their immunophenotype among SOC. Additionally, there is growing recognition of the substantial role social determinants of health play in driving health inequalities in SOC communities. It is critically important to understand that social determinants of health often play a larger role than biologic or genetic factors attributed to "race" in health care outcomes. Herein, we describe the structural, genetic, and immunological variations and the potential implications of these variations in populations with SOC. This article underscores the importance of increasing the number of large, robust genetic studies of cutaneous disorders in SOC to create more targeted, effective therapies for this often underserved and understudied population. Part II of this CME will highlight the clinical differences in the phenotypic presentation of and the health disparities associated with the aforementioned cutaneous disorders in SOC.

Comparison Between Trichoscopic and Histopathological Evaluations of Hair Parameters

Background

Collecting data on hair counts helps dermatologists diagnose hair diseases more accurately. Quantitative trichoscopy analysis and pathologic examination are two common ways to evaluate hair parameters.

Purpose

The study aims to compare the effect of quantitative trichoscopy analysis and pathologic examination in hair counting and quantify the hair density of average Chinese people.

Methods

Trichoscopy was performed in four scalp regions with a total of twenty-three volunteers without alopecia: frontal, vertex, occipital, and parietal. Hair density parameters were recorded. A 4-mm punch biopsy was performed in the occipital area, and all specimens were transversely sectioned serially and observed to calculate the hair densities.

Results

The average hair density, hairs per follicle unit, and vellus hair ratio from quantitative trichoscopy analysis in the occipital region were 163.07±28.17/cm², 1.87±0.25 and 6.60±3.95%, lower than those from biopsy significantly (214.97±48.73/cm², 2.24±0.30 and 10.48±6.43%). The hair shaft diameter measured by quantitative trichoscopy analysis was 74.52±8.02μm, higher than that by histopathologic examination (68.65±8.00μm) (p<0.05).

Conclusion

Quantitative trichoscopy is a noninvasive, quick, and convenient way to evaluate hair density. Histopathologic examination is an invasive way but provides more accurate data. The data obtained from trichoscopy and pathological examination are different to some extent, which cannot be substituted entirely for each other. This study established the reference for hair density in the adult Chinese population.

Clinical, trichoscopy, and light microscopic findings in hypohidrotic ectodermal dysplasia: Report of 21 patients and a review of the literature

INTRODUCTION

Hypohidrotic ectodermal dysplasia (HED) is a genetic condition typified by alterations in skin structures including sweat glands, hair, nails, and teeth. Hair findings in HED have been poorly characterized in larger series.

OBJECTIVE

To characterize scalp and hair findings of patients with HED clinically and with trichoscopy and light microscopy.

METHODS

A cross-sectional study in 21 pediatric HED patients was performed using available clinical and scalp dermatoscopic images, as well as pulled-hair samples for clinical evaluation, trichoscopic, and light microscopic analyses.

RESULTS

Seventeen out of 21 patients (81%) were men. Twenty patients had straight hair. Sixteen patients had decreased hair density, 6 of whom had hair loss mainly in the temporal and occipital regions. Fourteen patients had hair whorls. On trichoscopy, we observed: single-hair follicular units (n = 19, 90%), scalp hyperpigmentation (n = 13, 62%), variable diameter of the hair shafts (n = 12, 57%), perifollicular scales (n = 8, 38%), scalp erythema (n = 8, 38%), and short curly pigtail hairs (n = 6, 29%). On light microscopy, findings included: hair shafts with irregular diameter (n = 7, 33%), heterogeneous hair color (n = 6, 29%), trichoptilosis (n = 2, 10%), and pili torti (n = 1, 5%).

CONCLUSIONS

In this series, hair findings in HED were similar to those described in previous studies. However, we describe two new clinical and two trichoscopic findings: decreased hair density mainly in the temporal and occipital regions, oblique upwards occipital hair follicles orientation, angled hairs, and short curly pigtail hairs. These heterogeneous findings may reflect the multiple factors and signaling pathways that can be affected in these syndromes.

The study of hair follicle counts from scalp histopathology in the Thai population

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.

Evaluation of Hair Density and Hair Diameter in the Adult Thai Population Using Quantitative Trichoscopic Analysis

The data of hair density and hair diameter in the Asian population, especially in Thais, are limited. We aimed to evaluate hair density and hair diameter of members of the Thai population at different scalp sites and to determine the effect of sex and aging as well as to compare the results with those in groups of other ethnicities. Healthy Thais whose hair examination findings were normal were evaluated. Two hundred and thirty-nine subjects participated in this study, of whom 79 were male and 160 were female. Hair density and hair diameter were analyzed at four different scalp sites using quantitative trichoscopic analysis. The highest hair density in Thais was observed in the vertex area. Hair densities at four different scalp sites were significantly different from one another; only hair density at the vertex site showed no significant difference from that in the occipital area. In contrast, hair diameter did not show any statistically significant differences for the different sites. We observed decreased mean hair density with increasing age and found statistically significant differences between participants in their 20s and those in their 60s, while hair diameter remained consistent. Comparing our results with a previous study in other ethnicities, the hair densities in Asians are generally lower. In conclusion, hair density in the Thai population varies at different scalp sites. Aging is a factor in declining hair density. Asians have a lower hair density compared to Caucasian and African populations.