Trichoscopy

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 Editor: Anna Waskiel Burnat

 Author(s): Lidia Rudnicka, Anna Waskiel Burnat, Adriana Rakowska

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Description	This chapter describes dermoscopy of hair and scalp (Trichoscopy).
Author(s)	Lidia Rudnicka · Anna Waskiel Burnat · Adriana Rakowska
Responsible author	Anna Waskiel Burnat → send e-mail
Status	released
Status update	May 22, 2019
Status by	Ralph P. Braun

This chapter describes dermoscopy of hair and scalp (Trichoscopy).

It has the following subchapters:

Trichoscopy, Hair, Scalp Trichoscopy – cite! Trichoscopy (message) Trichoscopy – participate!

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Normal trichoscopy findings

Trichoscopy in healthy persons is characterized by:

1. Mean hair thickness more than 0,053 mm in the frontal area and more than 0,050 mm in the others (temporal and occipital)

2. Percentage of thin hairs less than 10% in the frontal and occipital area and less than 13% in the temporal areas

3. The percentage of pilosebaceous units with single hair less than 35% in the frontal area, 30% in the occipital area and 40% in the temporal areas

4. Yellow dots less than 4 in 4 fields of vision with 70-fold magnification in the frontal area and only 1 in the others

5. Perifollicular discoloration lower than 25% in the frontal area, lower than 15% in the occipital area and 20% in the temporal area

6. Pinpoint vessels in the frontal area (80% of patients) and thin arborizing vessels in occipital and temporal areas

Trichoscopic structures and patterns

Hair shafts

Fractured hairs

Trichoptilosis	Trichoschisis or trichoclasis	Broken hairs	Golf tee hairs
Longitudinal splitting of the distal end of hair shaft	A clean transverse fracture across the hair shaft	Irregular transverse fracture across the hair shaft	A hair with a concave distal end
Unspecific manifestation of a defect in hair shaft structure	Trichothiodystrophy, secondary to conditions that weaken the hair shaft	Trichotillomania, traction alopecia, alopecia areata, tinea capitis	Specific for Netherton syndrome

Narrowings

Monilethrix	Monilethrix-like congenital Hypotrichosis	Monilethrix-like hairs (Pohl-Pinkus constriction)	Pseudomonilethrix	Exclamation mark hairs	Tapered hairs
Hair with regularly distributed nodes and narrowings The nodes correspond to normal hair shaft thickness; the internodes are the narrowings	As in monilethrix, but the spaces between narrowings are extremely short	Hair with irregularly distributed narrowings (Pohl-Pinkus constrictions)	Differs from monilethrix—nodes appear thicker than the normal hair shaft and internodes have the thickness of the normal hair	Hairs with a thin, usually hypopigmented proximal end and thicker, pigmented distal end	Long exclamation mark hairs, the distal end is outside the field of view of a dermoscope
Specific for monilethrix	Specific for monilethrix-like congenital hypotrichosis	Alopecia areata, chemotherapyinduced alopecia, bleeding, malnutrition Artificial: monilethrix-like effect from hair styling gel or immersion fluid	Controversial	Alopecia areata, chemotherapyinduced alopecia, intoxication, trichotillomania	Alopecia areata, cicatricial alopecia, trichotillomania, bleeding, malnutrition, chronic intoxication

Node-like appearance

Trichonodosis (hair knotting)	Trichorrhexis nodosa	Trichorrhexis invaginata (bamboo hairs)	Hair casts (peripilar keratin casts)
A single or double knot in the hair shaft	A hair shaft with a restricted area where the shaft splits longitudinally into numerous small fibers The outer fibers bulge out, causing a segmental increase in hair diameter	The hair shaft telescopes into itself The proximal part of the abnormality is concave and the distal end is convex (bulging), producing an impression of nodular swelling along the hair shaft	Firm, white, tubular masses that encircle the hair shafts
No clinical significance	Multiple acquired and inherited diseases, commonly due to mechanical or chemical trauma	Specific for Netherton syndrome	A nonspecific finding, commonly associated with scaling or epidermal detachment Traction alopecia

Curls and twists

Pigtail hairs	Coiled hairs	Comma hairs	Corkscrew hairs	Zigzag hairs	Pili torti	Wooly hairs
Short, regularly coiled hairs with tapered ends	Irregularly coiled hairs with a jagged end When not fully coiled, they may have a hook-like appearance	Short, comma-like (C-shaped) hairs, homogeneous in thickness and pigmentation	Hairs with multiple twists and coils, forming corkscrew-like structures	Hairs, bent at sharp angles, form zigzag structures	Hairs that are flattened and twisted on their own axis at irregular intervals, usually through an angle of 180°	Hair shafts with waves at very short intervals, giving a crawling snake appearance
Alopecia areata	Trichotillomania	Tinea capitis	Tinea capitis	Tinea capitis, alopecia areata	Associated with multiple inherited and acquired hair diseases	Inherited syndromes

Bands

Continuous Medulla	Interrupted Medulla	Pili annulati	Interrupted (Morse Code-like) hairs
Longitudinal white band along the midpart of the hair shaft that covers less than 50% of the hair shaft thickness	Interrupted longitudinal white band along the midpart of the hair shaft The band covers less than 50% of the hair shaft thickness	Hair shafts with transverse light, blurry, whitish bands covering (nearly) the width of a hair	Hairs with multiple thin white bands across the hair shaft
Normal	Normal	Hair shafts with transverse light, blurry, whitish bands covering (nearly) the width of a hair	Tinea capitis

Short hairs

Upright regrowing	Vellus hairs	Dark lines	Tulip hairs	Block hairs	i-Hairs	Broom hairs	Broom fibers	Flame hairs
New, healthy, regrowing hairs that have a tapered end and a straight-up position	Short, thin, hypopigmented, delicate, nonmedullated hairs, usually somewhat wavy in shape	Thin, short, intensely pigmented hairs, appearing tapered at both sides	Short hairs with a tulip leaf-like hyperpigmentation at the distal end	Very short hairs with a transverse horizontal distal end	i-Hairs are block hairs with an accented dark distal end	Few or more linear, short hairs emerging from one follicular opening	Few or more linear, short, dark fibers (significantly thinner than terminal hairs) emerging from one follicular opening	Hair residues, semitransparent, wavy, and cone-shaped, resembling a fire flame
Normal; If abundant, may reflect a regrowth phase of telogen effluvium	Normal; If abundant, may reflect androgenetic alopecia	Noncicatricial alopecia	Trichotillomania	Noncicatricial alopecia associated with shaft hair fragility	Noncicatricial alopecia associated with high shaft hair fragility (eg, tinea capitis)	Observed in diverse entities, both cicatricial and noncicatricial	Observed in diverse entities, both cicatricial and noncicatricial	Trichotillomania

Hair follicle openings

"Dots" correspond to hair follicle openings observed in trichoscopic examination [1].

Black dots

Black dots, also known as “cadaverized hairs”, represent pigmented hairs broken or destroyed at scalp level [1]. They are commonly observed in alopecia areata [3], dissecting cellulitis [4, 5], trichotillomania [6] and tinea capitis [4]. Black dots may be also detected in chemotherapy-induced alopecia [4], lichen planopilaris [7], discoid lupus erythematosus [7], traction

"Dots" correspond to hair follicle openings observed in trichoscopic examination [1].

Yellow dots

Yellow dots correspond to follicular infundibula filled with sebum and/or keratotic material [10]. They present as yellow, or whitish, round or polycyclic dots, varied in size and uniformed in color, devoid of hairs or containing miniaturized, cadaverized or dystrophic hairs [10-12].
In alopecia areata, yellow dots are characterized by an abundant amount and regular distribution and predominate in long-lasting, inactive disease [3, 13].
The predominance of yellow dots (they are predominantly sebaceous) in the frontal area compared to the occipital area is characteristic for androgenetic alopecia [14]. They correspond to empty follicular openings of follicles in kenogen phase.
In discoid lupus erythematosus, large, dark yellow dots that correspond to wide infundibula filled with keratotic material are observed [1, 5].
Yellow dots, appearing as large "3D" soap bubbles imposed over dark dystrophic hairs are specific for dissecting cellulitis [1, 5].
Sparse yellow dots may also be detected in chronic telogen effluvium [8, 9], traumatic alopecia [8] traction alopecia [7], congenital hypotrichoses and kerion celsi [15].

Red dots

Red dots correspond to widened infundibula plugged by keratin and surrounded by dilated vessels and extravasated erythrocytes [16]. They are characteristic trichoscopic finding for active discoid lupus erythematosus and believed to be a positive prognostic factor [5].

White dots

There are two types of white dots.
The classic, big, irregular white dots correspond to areas of perifollicular fibrosis and are observed most commonly in lichen planopilaris [1].
The small, regular pinpoint white dots represent hair follicle openings and eccrine sweat gland openings and are observed in sun exposed areas and in dark skin phototypes regardless of hair loss [1].

Perifollicular and interfollicular skin surface

In trichoscopy, following perifollicular and interfollicular skin surface abnormalities may be observed: scaling, discoloration, discharge and surface structure.

Scaling

Epidermal scaling can be divided into perifollicular and diffuse [13].

Mild diffuse scaling may be observed in healthy persons with dry skin. White moderate to severe diffuse scaling is detected in psoriasis, discoid lupus erythematosus and contact dermatitis. Yellowish moderate to severe diffuse scaling is presented in seborrheic dermatitis, discoid lupus erythematosus and ichthyosis [13].

White perifillicular, tubular scaling is characteristic for lichen planopilaris. In folliculitis decalvans, yellowish, tubular with collar formation is observed [13]. It needs to be emphasized, that diffuse “scaling” with formation of white perifollicular clusters may be present in monoclonal gammopathy [13].

Discoloration

Brown areas in trichoscopy may occur in three different patterns.
Honeycomb pattern comprises a homogenous, mosaic or contiguous brown rings. It may be observed in chronically sun-exposed areas of thinning or complete hair loss and the scalp of dark-skinned patients [17]. Perifollicular brown coloration results from perifollicular lymphocytic infiltration [14] and is commonly detected in androgenetic alopecia, telogen effluvium. It may be presented in up to 10% of hair follicle openings in healthy persons [14, 18]. Scattered brown discoloration is typical feature of discoid lupus erythematosus [5].

Pink, “strawberry ice cream” areas are characteristic trichoscopic findings of cicatricial alopecia and correspond to early fibrosis [5].

Red areas may be observed in case of inflammation, extravasation, epidermal detachment and vascular abnormalities [13].

White areas are common feature of cicatricial alopecia and correspond to late fibrosing process [5]. They may be also observed in epidermal detachment and edema [13].

Yellow areas are detected in dissecting cellulitis, follicular pustules, dissecting cellulitis and bacterial infections [13].

Discharge

Yellow or yellow-red discharge is detected in folliculitis decalvans, bacterial infections, dissecting cellulitis or tinea capitis [13].

Surface structure

Starburst pattern hyperplasia results from fibrosis and is characteristic trichoscopic findings of folliculitis decalvans [5].

Blood vessels (scalp)

Comma vessels	Dotted vessels	Hairpin vessels	Elongated hairpin vessels	Straight linear vessels	Thin arborizing vessels	Thick arborizing vessels	Capillary blood extravasations	Concentric perifollicular vessels	Milky red globules	Linear helical vessels	Lace-like vessels	Glomerular vessels	Serpentine vessels	Thick root-like vessels	Vessel nets
C-shaped or slightly curved vessels	Tiny, red dots densely aligned next to each other	Small, linear looped vessels	Elongated, linear looped vessels	Straight linear vessels	Thinner than the average terminal hair arborizing vessels	Thicker than the average terminal hair arborizing vessels	Round or oval, sharply demarcated, intensely red areas	Vessels (loops or linear) arranged concentrically around a follicular unit	Globules or larger areas of a fuzzy or unfocused milky red color	Linear vessels twisted along a central axis	Combination of serpentine and looped vessels	Coiled or twisted vessels	Bending, scarcely branching vessels	Thick, irregularly banded, linear vessels	Interfollicular network of blood vessels
Inflammatory scalp diseases (seborrheic dermatitis, psoriasis), healthy persons	Healthy persons in the frontal area, eczema	Healthy persons in the frontal area	Cicatricial alopecia (lichen planopilaris, folliculitis decalvans), T-cell lymphoma	Pemphigus vulgaris	Healthy persons (the occipital and temporal area), seborrheic dermatitis	Discoid lupus erythematosus, basal cell carcinoma	Active psoriasis	Cicatricial alopecia (lichen planopilaris, folliculitis decalvans)	T-cell lymphoma, psoriasis	Psoriasis, pemphigus, T-cell lymphoma	Psoriasis	Psoriasis	Discoid lupus erythematosus	Discoid lupus erythematosus, congenital capillary malformations	Healthy persons, after topical corticosteroids