Trichoscopy: Essentials for the dermatologist

Table 1 Hair shafts

> 20% of vellus hairs	AGA, long lasting AA
Exclamation mark hairs	AA, trichotillomania, chemotherapy-induced alopecia
Pohl-Pinkus constrictions	AA, chemotherapy-induced alopecia, blood loss, malnutrition, chronic intoxication
Comma hairs	Tinea capitis
Corkscrew hairs	Tinea capitis
Coiled hairs	Trichotillomania
Flame hairs	Trichotillomania
Tulip hairs	Trichotillomania, AA
Regrowing pigtail hairs	AA, cicatricial alopecia
Zig-zag-shaped hairs	Tinea capitis

AGA: Androgenetic alopecia; AA: Alopecia areata.

Table 2 Dots

Black dots	Active AA, dissecting cellulitis, tinea capitis, chemotherapy-induced alopecia, trichotillomania, after laser depilation, after trichogram, incidental finding in other diseases
Yellow dots	AA: Marker of disease severity Discoid lupus erythematosus: Large, dark yellow to brownish-yellow dots Androgenic alopecia: "Oily" appearance and predominance in frontal area Dissecting cellulitis, trichotillomania: Imposed over dark dystrophic hairs
White dots	Primary folliculocentric alopecias, lichen planopilaris: Fibrotic white dots Dark skin, sun exposed areas: Pinpoint white dots
Red dots	Discoid lupus erythematosus, vitiligo
Pink-grey/grey dots	Frontal fibrosing alopecia (eyebrows)

AA: Alopecia areata.

Table 3 Peri- and interfollicular areas

Epidermal scaling	Diffuse scaling: Healthy individuals, psoriasis, seborrheic dermatitis Perifollicular scaling and tubular scaling structures: Lichen planopilaris, frontal fibrosing alopecia, folliculitis decalvans
Hyperpigmentation	Honeycomb: Sun exposed areas, dark skin phototypes Perifollicular: Androgenetic alopecia Scattered interfollicular: Discoid lupus erythematosus
Yellow or yellow-red discharge	Folliculitis decalvans, bacterial infections, dissecting cellulitis, tinea capitis
Structural changes in the skin surface	Starburst pattern hyperplasia in folliculitis decalvans

Table 4 Trichoscopic findings in common types of non cicatricial alopecia

AGA	AA	Telogen effluvium	Trichotillomania
Hair shaft thickness heterogeneity	Exclamation mark hairs	Empty follicles	Simultaneous, chaotic coexistence of multiple hair shaft abnormalities
Increased proportion of vellus hairs	Broken hairs	Increased proportion of single-hair follicular units	Hairs broken at different lengths
> 10% thin hairs in the frontal area	Clustered short vellus hairs	Short regrowing hairs	Short hairs with trichoptilosis (split ends)
Increased proportion of single-hair follicular units	Pigtail hairs	< 20% hair diameter diversity	Coiled hairs
Yellow dots	Black dots	Brown perifollicular discoloration	Exclamation mark hairs
Perifollicular discoloration (peripilar sign)	Numerous yellow dots	No significant difference between frontal and occipital areas	Black dots
All the trichoscopic features appear most prominently in the frontal scalp area compared to the occipital area			Others: flame hairs, V-sign, hook hairs, hair powder and tulip hairs

AGA: Androgenetic alopecia; AA: Alopecia areata.

Table 5 Trichoscopic findings in common types of cicatricial alopecia

LPP	FFA	DLE
Intense perifollicular scaling, tubular structures	Minor perifollicular scaling	Large yellow dots (follicular keratotic plugs)
Violaceous inter or perifollicular areas	Perifollicular erythema	Mottled dyschromia
Fibrotic white dots	Strong predominance of single-hair follicular units at the hair-bearing margin	Thin and radial arborizing vessels that emerge from yellow dots (“red spider in yellow dot”)
Blue grey dots	Absence of vellus hairs	Thick arborizing vessels at the perifery ot the lesion
Small hair tufts	Pink-grey and grey dots in the lateral eyebrow area	Follicular red dots

LPP: Lichen planopilaris; FFA: Frontal fibrosing alopecia; DLE: Discoid lupus erythematosus.