Hair shafts
From dermoscopedia
This chapter describes dermoscopy of hair shaft anormalities as seen in trichoscopy
It has the following subchapters:
- 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]
