THE FOUR KEY POINTS OF TRICHOSCOPY
The use of trichoscopy for the evaluation and diagnosis of hair and scalp disorders has been established in recent years as an indispensable tool in the field of dermatology.
It is a noninvasive tool which allows for magnified observation of possible defects of the hair shaft, as well as of the hair follicle openings, as well as the perifollicular epidermis and the area’s blood vessels. Defects and abnormalities in the appearance of these four structural components of the scalp contribute in the differential diagnosis of hair loss, i.e. for the exclusion of disorders with similar symptoms and to finally detect the actual cause.
A. HAIR SHAFT
Structural abnormalities of the hair shaft may provide diagnostic clues for multiple acquired and hereditary causes of hair loss. For instance, hairs that look like an exclamation mark may indicate alopecia areata, trichotillomania and chemotherapy-induced alopecia. Similarly, hair that look like a comma – comma hairs – indicate a diagnosis of tinea capitis, while coled hairs are the main characteristic of trichotillomania. As far as Pohle Pinkus constrictions are concerned, hair in which there is a disruption of the medulla, these are a sign of alopecia areata, chemotherapy-induced alopecia, blood loss, malnutrition and chronic intoxication.
B. HAIR FOLLICLE OPENINGS
Hair follicle openings appear in trichoscopy as small round structures, called ‘‘dots’’ and their colour constitutes a significant point for diagnosis.
- Black dots are observed in 40% of patients with alopecia areata and are considered a marker of high disease activity. Nevertheless, black dots may be present in dissecting cellulitis, tinea capitis, trichotillomania and chemotherapy-induced alopecia. On the other hand, black dots are not present in healthy individuals or in patients with male pattern hair loss or telogen effluvium.
- Yellow dots are follicular openings filled with keratotic material and/or sebum. Distributed yellow dots are usually present in 60% of patients with alopecia areata and are considered a marker of major disease severity and less favorable prognosis. Large, dark yellow to brownish-yellow dots are considered as a characteristic of discoid lupus erythematosus. Furthermore, yellow dots are also seen in patients with male pattern hair loss, but they differ from the yellow dots observed in other diseases in terms of their ‘‘oily’’ appearance.
- White dots may appear either as as small, irregular fibrotic areas, observed in primary, folliculocentric cicatricial alopecias, and most commonly in lichen planopilaris, or as small spots on a contrasting, pigmented background, observed in healthy individuals with dark skin and in patients with noncicatricial alopecia.
- Red dots have been observed in patients with discoid lupus erythematosus and in individuals with vitiligo, while dots of pink-grey and grey colour have been observed in the eyebrows of patients with frontal fibrosing alopecia.
C. PERIFOLLICULAR AND INTERFOLLICULAR AREAS
In trichoscopy, the classification of perifollicular and interfollicular skin surface abnormalities is carried out based on features related to the following elements: scaling, colour, discharge, and surface structure.
- Epidermal scaling is a common finding in healthy individuals. However, intense and/or diffuse scaling it may be an indication of various types of inflammatory scalp diseases, such as psoriasis and seborrheic dermatitis.
- Scalp hyperpigmentation may appear in three different distribution patterns: honeycomb, perifollicular, and scattered interfollicular. Honeycomb hyperpigmentation is a normal finding in areas that have been exposed to the sun and in patients with Fitzpatrick skin phototypes IV, V, and VI. Perifollicular hyperpigmentation is common in patients with male pattern hair loss, while scattered hyperpigmentation is characteristic of discoid lupus erythematosus.
- Yellow or yellow-red discharge can be detected through trichoscopy and may be related to conditions such as folliculitis decalvans, bacterial infections and dissecting cellulitis.
- Structural changes in the surface of the skin can be detected through trichoscopy and may be related to conditions such as starburst pattern hyperplasia, a characteristic of folliculitis decalvans.
D. BLOOD VESSELS
- The significance of blood vessel abnormalities in the scalp has not been explored in detail so far. Nevertheless, according to a recently completed classification the following vessel types can be distinguished: elongated vessels in lichen planopilaris, thick arborizing vessels in discoid lupus erythematosus and glomerularor coiled vessels in linear or circular alignment in psoriasis.