what was distinctive about the end of europes african and asian empires compared to other cases

Clin Cosmet Investig Dermatol. 2020; thirteen: 309–318.

Asian Hair: A Review of Structures, Properties, and Distinctive Disorders

Kanchana Leerunyakul

ⁱDivision of Dermatology, Department of Medicine, Faculty of Medicine, Ramathibodi Hospital, Mahidol Academy, Bangkok, Thailand

Poonkiat Suchonwanit

^anePartitioning of Dermatology, Section of Medicine, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand

Received 2020 Jan 27; Accustomed 2020 Apr 8.

Abstract

Asian hair is known for its straightness, dark pigmentation, and big diameter. The cuticle layer in Asians is thicker with more compact cuticle cells than that in Caucasians. Asian hair generally exhibits the strongest mechanical properties, and its cross-sectional area is determined greatly by genetic variations, specially from the ectodysplasin A receptor gene. However, knowledge on Asian hair remains unclear with limited studies. This commodity aimed to review and summarize the characteristics and backdrop of Asian pilus. Information technology likewise aimed to hash out hair disorders including linear lupus panniculitis and pseudocyst of the scalp that occur distinctively in Asian populations.

Keywords: alopecia, biogeographic population, ethnicity, pilus loss, hair shaft disorders

Introduction

Human pilus is one of the significant parts of the human body that reflects an individual's appearance and identity. The diversity of human hair is the result of different genetics and demographic backgrounds together with hair grooming and cultural practices. Understanding the differences in hair morphologies, structures, and properties among various populations is important for clinicians to provide a right diagnosis and treatment as hair disorders present and progress differently. Human hair is generally categorized into three major groups according to indigenous origins, ie, Asian, African, and Caucasian. Each ethnic group possesses different hair features including hair thickness, curvature, pigmentation, and mechanical backdrop.

Currently, knowledge on Asian hair remains unclear due to limited studies. This review aimed to summarize the characteristics and properties of Asian hair and present hair disorders exclusively described in Asian population. It is based on a systemic literature search of published manufactures from the MEDLINE database via PubMed using specific search terms "Asian," "race," "ancestry," and "ethnic" combined with "pilus" and/or "alopecia." We conducted a transmission enquiry of each article's reference list to ensure a more consummate sample of existing literature.

Characteristics of Asian Hair

Hair in Asian population shows a distinctive appearance of existence straight, round, and having black or brown pigmentation.¹ Compared with Caucasian and African hairs, Asian hair shows multiple unique structures and properties. The comparisons of hair characteristics amongst the three major ethnic groups are summarized in Table ane.ⁱⁱ ^– ⁸

Table i

Comparisons of Hair Characteristics Among Three Major Indigenous Groups

	Asian	African	Caucasian
Hair density	175 ± 54 hairs/cm²	161 ± l hairs/cm^two	226 ± 73 hairs/cmⁱⁱ
Cross-exclusive expanse	4804 ± 159 µm^two	4274 ± 215 µm²	3857 ± 132 µm²
Hair curvature and shape	Relatively straightest Round cross-section	Curliest/screw Ellipsoidal cantankerous-department	Straight to curly Circular to oval cross-department
Pilus pigmentation	Blackness/brown Mainly eumelanin	Black/brown Mainly eumelanin	Dark-brown/blond: mainly eumelanin Blood-red: mainly pheomelanin
Hair growth charge per unit	411 ± 53 µm/mean solar day	280 ± 50 µm/day	367± 56 µm/solar day
Lipid content and hydration	Polar lipid and gratis fatty acid	Apolar lipid	Polar lipid and free fatty acid Greatest moisture content
Integrity	Endurable to stress and strain Stretching: stronger than Caucasian pilus	Most fragile No report of response when expose to stretching	Comparable force with Asian hair in response to stress and strain

Hair Shaft Structure

Hair shaft, mainly made up of keratin materials, consists of 3 layers, namely, the cuticle, cortex, and occasionally medulla. The medulla is located at the center, surrounded by the cortex, which is the primary structure of the hair shaft. The cuticle is the outermost layer that functions as a bulwark against physical and chemical damage.

Cuticle

The cuticle layers are composed of multiple sheaths of flat overlapping cells and cell membrane complex (CMC) between the cuticle cells. Cuticle cells are modest keratinized cells with a mean length of sixty µm and a thickness of most 0.5 µm.⁹ They are more meaty with a higher number of cell layers. A report found that the Asian's cuticle has a statistically significantly greater number of cuticle layers in 1 transverse section compared with the Caucasian'due south cuticle.¹⁰ ^, ¹¹ Although the total cuticle layers are significantly thicker in Asians, the thickness of one layer is specially similar betwixt the two ethnicities.¹¹ A recent study with larger samples agreed that Asian hair has a college median cuticle thickness than Caucasian and African hair.¹² The cuticular inclination of Asian hair is steeper than that of Caucasian hair, while the interval between each cuticle is wider. The Caucasian's cuticle is more fragile and tends to collapse into small pieces when exposed to extension stress.⁸ ^, ^ten By contrast, the Asian's cuticle has the ability to maintain its original shape and peels off as large fragments under stress or during the stretching procedure.⁸ ^, ^ten Among the 3 biogeographic populations, the cuticle layers closely attached more in Asian and Caucasian hairs, while instances of cuticle layer separation occur in African hair. Moreover, the African hair shows a college incidence of cuticle damage.¹²

Cortex

With regard to the cortex of the pilus shaft, cortical cell structures generally comprise macrofibrils, remnants, and pigment granules. Macrofibrils are the major components made upwards of intermediate filaments (IF) or microfibrils, which are cross-linked with keratin-associated proteins and embedded in the baggy materials called matrix.¹³ With regard to the gross diversity of hair amongst the three ethnicities, keratin filament structures are consistent.^xiv Depression-sulfur proteins and amino acrid composition establishing keratin filaments are invariable.¹⁵ ^, ¹⁶ Studies with X-ray scattering analysis did not observe whatever differences in the structures and configurations of the proteins (α-helical arrangements, coiled-roll structures, IF, and macrofibrils) beyond major biogeographic origins.^three ^, ¹⁴ In addition, the differences between wet and dry out states among pilus types observed from the lipid diffraction via Ten-ray scattering analysis indicated a variation of crystalline lipid structures among different pilus origins.¹⁴

Cross-Sectional Expanse

Asian hair has the greatest cross-exclusive area amidst the three human hair types. African and Caucasian hairs accept relatively equal cross-sectional areas that are smaller than Asian hair.¹ ^, ³ Asian hair possesses the most circular cross-sectional shape and the greatest mean ellipticity, calculated based on small-scale bore and large diameter ratio, indicating that it is more oval than African and Caucasian hairs.³

Genetic studies found that hair thickness in Asian populations is linked to genetic variations. Fujimoto et al observed a correlation between a nonsynonymous single nucleotide polymorphism (SNP) in ectodysplasin A receptor (EDAR) factor and hair thickness in Asians in a genome-wide analysis.¹⁷ The SNP (rs3827760) is located at the 1540th nucleotide from the transcription site (1540T/C) in the EDAR gene causing the commutation between valine and alanine (p.Val370Ala) and shows a stiff positive selection in Asians in several studies.¹⁷ ^, ¹⁸ The 1540C allele has loftier frequency only in Chinese and Japanese, but not in Nigerian or European ancestry.¹⁷ The 1540T/C shows a significant association with the cross-sectional area and hair diameter in Thais and Indonesians, whereas Melanesians, whose pilus diameter is similar to African and European hairs, show a lesser 1540C allele frequency.¹⁹ The cross-sectional area of pilus is associated with the diverseness of genotypes rather than the individual's ethnicity, and EDAR gene is a stiff determinant of hair thickness in Asians.¹⁷ ^, ^xix CC genotype was reported with the highest values of mean area, followed by TC and TT genotypes, respectively. Subsequent research confirmed that EDAR gene is a genetic contributor of hair thickness every bit the EDAR370A (1540C)-derived cells demonstrate a superior ability to activate NF-κB expression and enhancement of signal potency compared with the EDAR370V (1540T)-derived cells.²⁰ In vivo, transgenic mice with EDAR370A expression produce their hair phenotype mimicking the Asian pilus fiber. The high output from EDAR370A may influence the hair morphology in Asian populations. Also, the pilus thickness in Asian populations is besides linked to the FGFR2 polymorphism. Multiple regression assay when because the effect of EDAR revealed the significant associations of both hair bore and cross-sectional area, and the SNP in FGFR2 (rs4752566).²¹

Hair Curvature

Hair curvature is greatly diverse amid different indigenous populations. In contrast to African pilus that is more flattened and often has twists and turns, Asian pilus tends to exist round in shape, directly, and more cylindrical.¹ ^, ²² The low values of average curvature in Asian hair suggest a relatively straight hair. There are multiple proposed mechanisms of hair curvature: uneven expression of hair keratins in the precortex; asymmetrical distribution of proliferating cells and unbalanced proliferative compartment of the hair follicle; uneven bilateral distribution of cortical cell types that are adamant by the unlike arrangements of IF within the cortical cells; inner root sheaths incorporated in shaping pilus fiber; and differences in dermal papilla shape that influences hair curl.²³ ^– ²⁵

Hair Straightness

Hair straightness is i of the morphological features that are diverse amid races, implying an influential genetic linkage. A genome-broad browse exhibited a significant association between EDAR370A variant and hair straightness in E Asian populations.²⁶ EDAR370A was owing to three.66% of the total variance.²⁷ On the other hand, a genome-wide analysis in Europeans found that the trichohyalin (TCHH) cistron variant is accounted for their direct hair phenotypes, although information technology explained but around half dozen% of the variance.²⁸ The TCHH gene does not show loftier frequency in East Asians. Likewise, the EDAR variant cannot explain the hair straightness in Europeans. A genome-broad analysis in admixed individuals with eastern and western ancestries (Uyghur population) revealed that EDAR tin explain hair straightness variation better and has a greater effect than TCHH. No interaction was institute between these ii genes, indicating their effects on hair straightness through different mechanisms.²⁷ In addition, recent genome-wide clan studies reported the links of gyre formation in African individuals to polymorphic variation in trichohyalin, a copper transporter protein CUTC, and keratin 74 of the inner root sheath.²³

Pilus Pigmentation

The diversity of hair pigmentation, as well as skin color, mainly results from various amounts of admixed eumelanin and pheomelanin. Dark hair contains a high level of eumelanin and a small level of pheomelanin. Blond pilus contains a depression level of eumelanin and a trace of pheomelanin, whereas red hair has low to medium levels of both eumelanin and pheomelanin.^v ^, ⁶ Follicular melanogenesis in the hair follicles is characteristically circadian as the melanogenic activity of follicular melanocytes is mainly coupled to the anagen phase of the pilus cycle.²⁹ The biosynthetic mechanism is regulated by several regulators including hormones, neurotransmitters, cytokines, growth factors, eicosanoids, cyclic nucleotides, nutrients, and the physicochemical milieu.³⁰ Positive regulators include melanocyte-stimulating hormones, adrenocorticotrophic hormone, β-endorphin, estrogens, androgens, prostaglandins, leukotrienes, endothelin 1 and iii, histamine, stem jail cell factor, bone morphogenic proteins, and vitamin D3.^xxx ^, ³¹ The nutritional factors L-tyrosine and L-dihydroxyphenylalanine that serve as substrates and intermediates of melanogenesis also act as positive regulators of melanocyte functions.³² Too, hair follicles and skin produce diverse substances and neuromediators including corticotropin-releasing hormone, proopiomelanocortin, melatonin, serotonin, and steroids that can affect hair physiology and pathology.³³ ^– ³⁶

The dark pigmentation is mostly determined by an eumelanin production from melanocytes residing in the basement membrane encircled past the dermal papillae. Losing a melanocortin 1 receptor (MC1R) function from the mutation leads to pheomelanin overproduction and reddish hair color phenotype. The loftier degree of polymorphisms in human MC1R had been reported, simply an Arg163Gln variant was detected merely in Asian, Indian, and African-Indian populations with great differences in frequency.³⁷ ^, ³⁸ The extraordinary loftier frequencies were observed in Due east and Southeast Asians.³⁸ Although the supportive evidence is not clearly elucidated, there is a presumption that the Arg163Gln variant may exist involved in pheomelanin production in these populations.³⁸

Size and density of melanosomes in a pilus fiber contribute to hair pigmentation. Black hair has the largest melanosome and tightly packed eumelanin content. Brown hair has a smaller melanosome with ellipsoid shape.⁴ Hairs from individuals with African descendants display larger melanosome size and higher melanosome density than those of Caucasians and Asians.¹² A study demonstrated that human pilus becomes darker with age.³⁹ The finding was considerably affected by the increase in total melanin amount correlating to the enlargement of the melanosome size.^xl Further inquiry regarding melanosome is advocated to identify genetic markers and improve knowledge of human being hair pigmentation.

Hair Growth Rate

Asian hair shows the fastest growth charge per unit in comparison to the other two hair types. African hair has the everyman growth charge per unit.² ^, ⁴¹ Hair growth rate and pilus diameter were reported to be associated with cuticle interscale distance. Hairs with larger cross-sectional expanse abound faster and have a shorter cuticle interscale altitude, and vice versa. This relationship was reported in Asians and Caucasians with straight or semi-direct hairs.⁴² The cuticle interscale altitude of the wavy hair shafts exhibits high variations amid convex and concave regions. Hence, it can be inferred that a curly pilus would grow with a different rate correspondent to various cellular partition rates in the convex and concave parts.⁴²

Lipid Content and Hydration

In 2003, Franbourg et al found that African hair has a lower radial swelling percent in water compared with Asian and Caucasian hairs, which leads to a possibility of lipid differences among ethnic pilus types.³ To appointment, few studies take evaluated the differentiation on hair lipids among human populations. Pilus lipid components can be separated into internal and external lipids according to their origins. Internal lipids are biosynthesized inside the hair matrix cells and mostly comprise free fatty acrid (FFA), cholesterol, and polar components, such equally ceramide, cholesterol ester, and cholesterol sulfate. External lipids, including sterol esters and squalene, are known to ascend from the surface sebaceous lipids.⁷ ^, ⁴³

Experimental results showed that among the three ethnicities, African hair has the largest amount of total hair lipid extractions, followed by Caucasian and Asian hairs.⁴³ The lipids in African pilus mainly come up from the sebaceous lipids, and those in Asian and Caucasian hairs mainly come from the internal lipids.⁴³ However, African hair still has ane.7 times greater internal lipid contents than the other two indigenous groups.¹³ With regard to percentages over weight of whole fibers, contents of FFA, sterol, and polar lipids are the highest in African hair.^vii ^, ^thirteen The internal lipids were postulated to intercalate the keratin dimers and influence the organization of keratin fibers, which may lead to various hair morphologies.¹³ ^, ¹⁴ In relation to the external lipids, African fiber presents the greatest proportion of apolar lipids, and Asian and Caucasian extracts show a higher amount of FFA and polar lipids.^seven The high amount of apolar lipids with hydrophobic property in African fiber is associated with lesser swelling in water as it blocks the entrance of water into the pilus.³ ^, ¹³

Integral hair lipids located in the CMC of pilus cuticle layers are accountable for hair integrity, maintenance of hydrophobicity, wet, and hair stiffness. All three hair origins similarly show a smaller amount of lipids in the cortex compared with the cuticles.⁷ Asian hair demonstrates a greater corporeality of integral lipids than the other two indigenous hairs, which exhibit bottom damage to ultraviolet irradiation. In addition, Takahashi and Yoshida detected glycoside-like lipids (specially Due north-acetyl glycoside) in Japanese female hairs at the interface betwixt the cuticle and the cortex producing an adhesive effect between the ii layers.⁴⁴ They also found unsaturated fatty acids, such as linoleic acrid and alpha-linoleic acid, that reside in the hair seedling and melanin granules. The alpha-linoleic acid-derived oxidative metabolites comprise tightly in the melanin granules, implying the possibility of their participation during melanosome synthesis and melanogenesis.⁴⁴

Among homo races, Caucasian cobweb is the most hydrated ane, which is dissimilar from African and Asian hairs that relatively have similar moisture content.⁴³ Asian and Caucasian hairs demonstrate lower permeability due to lower diffusion coefficients compared with African hair.^seven ^, ⁴³ Optimum permeability is important in preserving humidity retention of the fiber from existence modified by a rapid change of h2o uptake and desorption. When the lipid was extracted, Caucasian hair was shown to have the greatest decreased hydration despite higher contents of lipid extraction in African fiber. Asian and African hairs share the same reduction level in moisture content. The diminution of water was speculated to be related to lipid saturation degree or the internal lipid content rather than the total amount of lipids.^seven ^, ⁴³

As the lipids are involved in keratin conformation, they may contribute to hair tensile strength. Lipid extraction does not affect African cobweb'south mechanical backdrop, simply decreases deformation at the break of Asian pilus and increases the pause tenacity of Caucasian hair.⁷ Lipid diminution may decrease matrix plasticity leading to the lower full general mechanical property of Asian hair.⁴³

Mechanical Backdrop

Mechanical properties vary among different ethnicities. Asian hair demonstrates the highest hardness and elastic modulus, followed by Caucasian and African hairs, respectively. All 3 hair types that were studied in this research presented a decrease of both properties at the hair tip due to cuticle damage.⁴⁵ Compared with Asian and Caucasian hairs, African pilus is more fragile, which is associated with lower breaking stress and lower breaking elongation of fibers. It requires the earliest breaking fourth dimension and a lower stress at breaking. With regard to the influence of hair size, Asian and Caucasian hairs showroom like response to stress and strain even though Asian pilus has a bigger cross-sectional area.³ The fragility of African pilus accompanied past traumatic hairstyles leads to a high prevalence of hair shaft abnormality in the African population.²² By contrast, the pilus shaft disorder is less problematic and uncommon in Asians.

Stretching of hair can distort hair structure as well as its properties. A study conducted on Asian and Caucasian hair samples observed the elevated level of cysteine residues, indicating disulfide bond ruptures from cysteine oxidation during the stretching process.⁸ Equally the stretching ratio increases, the α-helix conformations in the fibers transform into β-pleated sheets, β-turn structures, and matted content. The β-plough structures are easier to retract against the increased stretching ratios and may have a secondary transformation to the β-pleated sheets.⁸ ^, ⁴⁶ The matted content represents the destroyed macromolecular structures of fibers. Asian pilus has greater stability than Caucasian hair due to its larger diameter and its power to easily transfer to β-turn structures. The disordered content in Caucasian hair is raised at lower stretching ratios compared with that in Asian pilus.⁸

Hair Damage from Chemic Products

Chemical products, such as hair bleaching and hair dye, can alter hair shaft morphology and its properties. The cortex from the three major ethnic groups shows a similar response to straightening and coloring handling, but African hair exhibits greater tolerance to combination treatment (straightening and coloring). Hairs from all studied indigenous groups demonstrate like patterns of CMC damage after straightening and combination handling, but Asian pilus displays a bulged CMC and has lesser endurance than the others after treatment of coloring products.⁴⁷ Nevertheless, the cuticle's forcefulness confronting chemical treatments is inconclusive due to disagreeing outcomes in existing studies.⁴⁷ ^, ⁴⁸ Therefore, more research focusing on hair strength and hair change from the styling is warranted to provide a better understanding of Asian hair.

Hair Disorders in Asian Populations

Diagnosis and management of hair and scalp disorders take always been a challenge for dermatologists. Increasing evidence suggests that the prevalence, likewise as clinical presentation and severity of diseases, vary greatly among different ethnicities. This section discusses the dissimilar characteristics of common and distinct hair disorders in Asian populations.

Not-Scarring Alopecias in Asians

Androgenetic alopecia (AGA) and female blueprint hair loss (FPHL) are mutual non-scarring alopecia in Asian population. Several studies performed on Asians reported a lower prevalence of AGA and FPHL compared with the Europeans.⁴⁹ ^– ⁵² The evolution of AGA in Japanese men is approximately x years slower than that in Europeans, with 1.4-times lower in prevalence in each decade.⁵¹ Past contrast, the prevalence of AGA in Thais is higher and relatively similar to Caucasians, suggesting that the prevalence may be influenced past various genetic backgrounds.⁵³

Alopecia areata affects 0.1–0.2% of the population worldwide.⁵⁴ Most Asian patients experience the onset during their get-go four decades of life. The mean historic period of onset is like to Caucasians. Family history and vitiligo in Asians are lesser associated compared with the Westerners, but the percentages of autoimmune thyroid diseases are comparable.⁵⁵ ^, ⁵⁶

Tinea capitis is another mutual hair trouble worldwide and is acquired by Trichophyton and Microsporum spp. Etiologic agents diversely depend on the regions. In Asians, the near common causative organisms are Trichophyton ferrugineum and Trichophyton violaceum.⁵⁷ The prevalence of tinea capitis in African populations is higher compared with that in Asian populations. The triglyceride-rich sebum production in adults was hypothesized to have a fungistatic outcome creating a greater innate protection against ecthotrix fungal infections and a lower prevalence compared with that in children.⁵⁷ Therefore, it may be plausible that the lower prevalence in Asians is associated with different types and a lower corporeality of lipid content. Other contributing factors to fungal infection are pilus care practices. A low frequency of shampooing links to decreased spore disposal. The traction hairstyle in Africans allows easier access to mucus.⁵⁷ ^– ⁵⁹

Scarring Alopecias in Asians

Scarring or cicatricial baldness results from irreversible injury of follicular stem cells and replacement of hair follicles with fibrous tissues or hyalinization of collagen. Primary scarring alopecia (PSA) is characterized by an idiopathic folliculocentric inflammation that leads to a permanent hair follicular destruction. Secondary scarring alopecia is caused by inflammatory infiltrates of scalp skin that harm their nearby hair follicles.⁶⁰

According to the North American Hair Inquiry Gild, PSA can be classified into 3 groups: lymphocytic, neutrophilic, and mixed inflammation.⁶¹ Caucasians including Hispanics take high proportions of lymphocytic PSA compared with other indigenous groups, with PSA from 4:i to 8.2:1.⁶² ^, ⁶³ Diseases with neutrophilic or mixed PSAs are known to predominantly agonize African populations.²² A recent retrospective study of PSA in Taiwanese patients reported that the ratio of lymphocytic to neutrophilic PSA is ane.2:i. Lymphocytic PSA has a female person predominance, and neutrophilic PSA mainly affects males with younger historic period of onset.⁶⁴ By contrast, a study from China reported a ratio of lymphocytic to neutrophilic PSA of 1:1.three. Neutrophilic PSA too occurs more than in men, but mostly in their middle historic period.⁶⁵ Altogether, nosotros observed a trend of lymphocytic PSA in older females, and neutrophilic PSA in young males. Dissimilar Asians, Caucasians are dominated with lymphocytic PSA, eg, lichen planopilaris and chronic cutaneous lupus erythematosus.

The curly and frizzy pilus of African populations, together with markedly curved hair follicles and manipulation cause hairs to curl back into the dermis, which then leads to a strange-torso reaction. Therefore, pseudofolliculitis barbae and acne keloidalis nuchae, which are characterized past an "ingrown hair" inflammation, have the highest prevalence in African populations, followed by the Hispanic and Asian populations.²² ^, ⁶⁶ Moreover, androgen-dependent follicular occlusion diseases, such as dissecting cellulitis of the scalp (DCS), are significantly found more in African populations than in other populations.²² We speculate that the genetic variations may play a function in androgen level amending, unequal lipid contents of the hair and scalp among unlike ethnicities, and pathophysiology of diseases.

Given the lower pilus tensile forcefulness combined with the high degree of curl and dryness, African hair fibers are more than vulnerable to damage from daily traction-producing hair cares compared with Asian hair. These properties are speculated to exist the causes of cardinal centrifugal cicatricial alopecia (CCCA) and traction alopecia.²² ^, ⁶⁶ ^, ⁶⁷ Excessive hair intendance practice too leads to a higher incidence of hair shaft abnormalities in Africans including acquired trichorrhexis nodosa and chimera pilus.²²

Exclusively Described Hair Disorders in Asians

Linear Lupus Panniculitis of the Scalp

Linear lupus panniculitis of the scalp (LLPS) or linear and annular lupus panniculitis was firstly described by Nagai et al.⁶⁸ It is a rare entity that manifests as chronic not-scarring alopecic patches that follow the Blaschko'due south lines. The morphologies of LLPS lesion are linear, annular, and arch-shaped (Effigy one), and LLPS can be found in whatever area of the scalp. Erythema, atrophic change, and follicular plugging may accompany the alopecic surface area.⁶⁹ ^, ^lxx The LLPS has a predilection for Asians with few reports in Caucasians.⁶⁹ ^, ⁷⁰

An external file that holds a picture, illustration, etc. Object name is CCID-13-309-g0001.jpg

Linear lupus panniculitis of the scalp: non-scarring alopecic patch in a linear configuration.

Genetic predisposition may exist associated with this disorder that is predominantly institute in Asians. Histopathologically, the lesion is characterized by a lobular panniculitis with mainly lymphocytic infiltrates, mucin deposition, hyaline fat degeneration, and fat necrosis. The dermis shows abnormality with lymphocytic infiltration effectually the follicles, eccrine glands, and vessels. Granular degradation of IgM, IgG, and C3 can be observed at the peribulbar area and along the basement membrane past straight immunofluorescence in some cases. Patients with LLPS generally accept a good prognosis and a complete recovery after treating with oral hydroxychloroquine and oral/intralesional corticosteroids. Only a few patients have partial response or recurrence.⁶⁹ ^, ⁷⁰ The disease rarely develops systemic involvement. Half of the cases take positive antinuclear Antibody titer, but none of the reported cases evidence any sign of systemic lupus erythematosus.⁶⁹

Pseudocyst of the Scalp

In 1992, Iwata and Niimura described 19 Japanese patients with pseudocyst of the scalp (PCS) represented as a solitary reddish nodule that might exist associated with pain then gradually evolved into a dome-shaped mass with alopecia. Some lesions are bloody, yellowish-fluid, or purulent discharge.⁷¹ Abdennader et al later proposed another name called "alopecic and aseptic nodules of the scalp (AANS)," suggesting that it was more suitable for describing the condition. PCS predominantly affects immature Asian men with unknown prevalence.⁷² ^, ⁷³ Patients are clinically present with one or few, oft asymptomatic, nodules that are implicated with non-scarring alopecia and surrounded by an expanse of normal skin (Figure ii). In contrast to DCS, AASN lesions are unremarkably non-fluctuating.⁷² Some authors believed that PCS and AANS are two different diseases; nevertheless, nigh of them agreed that both conditions take the aforementioned entity with a varied histopathologic spectrum.⁷² ^, ⁷⁴ A well-divers subcutaneous hypoechoic nodule was observed using ultrasonography.⁷⁵ A positive puncture tin exist constitute in both atmospheric condition with varied material. The content inside the lesions is e'er sterile with negative microbiological cultures. Histopathologically, a pseudocyst formation is non always nowadays, but it is always observed in the PCS.⁷² The presence of pseudocyst was suspected to be influenced by the severity and elapsing of the inflammatory procedure and developed as a secondary change.⁷⁴

An external file that holds a picture, illustration, etc. Object name is CCID-13-309-g0002.jpg

Pseudocyst of the scalp/alopecic and aseptic nodules of the scalp: soft and dome-shaped alopecic nodules, slightly erythematous and pustules on surface, surrounded by an area of normal pare.

The etiology remains questionable. Some authors assumed that it was a spectrum of follicular occlusions that cause deep folliculitis, leading to not-scarring alopecia and eventually a pseudocyst formation. Some believed that the follicular occlusion was only a predisposing gene every bit it was not observed in every case. In our opinion, the PCS/AASN could be a minor severity spectrum of DCS with milder inflammation and less noticeable follicular occlusion. Nosotros hypothesized that the unlike racial or genetic backgrounds may exist associated with the variation every bit Africans tend to have neutrophilic PSA with college severity compared with Asians. Meanwhile, the inflammation targeting the hair follicles may be induced past an immune process and the reaction may secondarily develop from a follicular modification, a foreign body or an unknown factor.⁷² ^, ⁷⁶ PCS/AASN shows a good response with a spontaneous resolution after treatments of doxycycline 100 mg/d for at least three months, repetitive aspiration, or surgical excision, and other alternatives including intralesional corticosteroids and topical iii% indomethacin.⁷¹ ^, ⁷² ^, ⁷⁶

Conclusion

Asian pilus presenting every bit a cylindrical and straight cobweb with black or brown coloration is one of the renowned characteristics that distinguish among the three major indigenous origins. This review provides the currently available cognition and presents various interesting points of view of Asian hair, including characteristics, morphological features, and singled-out hair disorders involving Asian populations. However, much remains to exist explained regarding differences in pilus microstructures, genetics and diseases. Therefore, farther clinical inquiry is encouraged to assistance gain meliorate knowledge on the nature of Asian hair and pilus disorders.

Ideals and Consent Argument

The patients provided written informed consent to perform all necessary investigations, to accept clinical photographs, and to use them for research purposes and publication.

Disclosure

The authors study no conflicts of interest in this piece of work.

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