Hair and scalp

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Trichoscopic structures and patterns

Hair shafts

• A normal terminal hair are more than 55 µm wide and are uniform in thickness and color [1].
• The trichoscopic classification of hair shaft abnormalities is proposed by Rudnicka et al. [2].

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

Adapted from Rudnicka et al. [2]