This chapter describes dermoscopy of hair and scalp (Trichoscopy).
It has the following subchapters:
- 1 Normal trichoscopy findings
- 2 Trichoscopic structures and patterns
- 3 Perifollicular and interfollicular skin surface
- 4 Blood vessels (scalp)
- 5 Aqcuired nonscarring alopecia
- 6 Primary cicatricial alopecia
- 7 Inflammatory scalp diseases
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
|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|
|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|
|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|
|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|
|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 .
Black dots, also known as “cadaverized hairs”, represent pigmented hairs broken or destroyed at scalp level . They are commonly observed in alopecia areata , dissecting cellulitis [4, 5], trichotillomania  and tinea capitis . Black dots may be also detected in chemotherapy-induced alopecia , lichen planopilaris , discoid lupus erythematosus , traction
"Dots" correspond to hair follicle openings observed in trichoscopic examination .
Yellow dots correspond to follicular infundibula filled with sebum and/or keratotic material . 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 . 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  traction alopecia , congenital hypotrichoses and kerion celsi .
Red dots correspond to widened infundibula plugged by keratin and surrounded by dilated vessels and extravasated erythrocytes . They are characteristic trichoscopic finding for active discoid lupus erythematosus and believed to be a positive prognostic factor .
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 .
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 .
Perifollicular and interfollicular skin surface
In trichoscopy, following perifollicular and interfollicular skin surface abnormalities may be observed: scaling, discoloration, discharge and surface structure.
Epidermal scaling can be divided into perifollicular and diffuse .
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 .
White perifillicular, tubular scaling is characteristic for lichen planopilaris. In folliculitis decalvans, yellowish, tubular with collar formation is observed .
It needs to be emphasized, that diffuse “scaling” with formation of white perifollicular clusters may be present in monoclonal gammopathy .
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 . Perifollicular brown coloration results from perifollicular lymphocytic infiltration  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 .
Pink, “strawberry ice cream” areas are characteristic trichoscopic findings of cicatricial alopecia and correspond to early fibrosis .
Red areas may be observed in case of inflammation, extravasation, epidermal detachment and vascular abnormalities .
White areas are common feature of cicatricial alopecia and correspond to late fibrosing process . They may be also observed in epidermal detachment and edema .
Yellow areas are detected in dissecting cellulitis, follicular pustules, dissecting cellulitis and bacterial infections .
Yellow or yellow-red discharge is detected in folliculitis decalvans, bacterial infections, dissecting cellulitis or tinea capitis .
Starburst pattern hyperplasia results from fibrosis and is characteristic trichoscopic findings of folliculitis decalvans .
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|