Introduction
Many scalp and hair disorders present with focal hairless patches which require meticulous examination to differentiate between cicatricial (scaring) and noncicatricial (non-scarring) alopecia and to identify their exact cause. Trichoscopy can be used as a non-invasive tool for rapid diagnosis of different types of alopecia.
Main causes of localised noncicatricial alopecia:
- Alopecia Areata (AA)
- Tinea Capitis (TC)
- Trichotillomania (TM)
- Tractional alopecia
- Temporal Triangular Alopecia (TTA).
Alopecia areata
Refer to generalised noncicatricial hair loss for further information on the trichoscopy of alopecia areata.
Tinea capitis
Tinea capitis is a superficial fungal infection of the scalp commonly affecting children, however it may present in immunosuppressed adults. The disease is primarily caused by dermatophytes, Trichophyton and Microsporum genera, that cause endothrix or ectothrix type hair shaft infection respectively.
The clinical presentation is typically of a single or multiple patches of hair loss, sometimes with a black dot pattern, that may be accompanied by inflammation, scaling, pustules, and itching.
Trichoscopic features
Specific features:
- Comma hairs
- Corkscrew hairs.
Comma and corkscrew hairs represent the bending of the affected hair shafts due to the invasion with fungal hyphae.
Other features:
- Heterogeneous black dots
- Broken and dystrophic hairs
- Zigzag hairs
- Morse code (barcode) hairs are reported: clue of ectothrix infection by Microsporum canis
- White or yellow greasy scales
- Erythematous perifollicular skin, V-shaped hair, crusts, and follicular pustules are observed in inflammatory types
- Follicular keratosis in non-inflammatory type
Dermoscopic image of tinea capitis showing zigzag hairs; focal weakening of the hair shaft in a male child
Dermoscopic image of tinea capitis showing morse code–like hair; interrupted hairs with multiple bands along the hair shaft in a female child.
Dermoscopic image of corkscrew hairs (white circles) with yellowish greasy scales (red arrows) denoting tinea capitis.
Trichotillomania
Trichotillomania is a body-focused repetitive behaviour disorder. Sufferers may derive pleasure, gratification, or relief when pulling out their hair. It presents with irregular patches of alopecia, with hairs of variable length commonly affecting the vertex or parietal scalp.
Trichoscopic features
Specific features:
- Hairs broken at different lengths
- Irregular coiled hairs
- Flame figures frequently in early childhood patients
- V-sign
- Hair powder.
Dermoscopic image of trichotillomania showing flame figures; hair remnants of recently pulled hairs
Trichotillomania showing V-sign that represents two hair shafts emerging from the same follicle and cut at the same level
Dermoscopic image showing hair cut at different levels (white arrows), hook hair (black arrows) and flame figures (red arrows) denoting trichotillomania
Other features:
- Heterogeneous black dots
- Hook hairs
- Trichoptilosis
- Extravasated blood
- Tulip hairs
- Upright regrowing hairs
- Yellow dots with cadeverized hair in the center
- Micro–exclamation mark hairs are sometimes described
- Pluck-out sign is described in beard trichotillomania as presence of hemorrhages around the hair follicles
- Less common: comma hairs, crusts, scales, dirty dots, and honeycomb pigment network.
Traction alopecia
Refer to trichoscopy of generalised noncicatricial hair loss for further information on the trichoscopy of tractional alopecia.
Temporal triangular alopecia
Temporal triangular alopecia is a non-scarring, circumscribed alopecia is often located unilaterally in the frontotemporal region during early childhood and remains stationary throughout life.
Trichoscopic features
- Normal follicular openings.
- Vellus hairs of variable length and white hairs are reported.
- Central tuft of terminal hairs may be present in some patients.
- Absent characteristic features suggestive of other disorders.
