ReviewHair and scalp dermatoscopy
Section snippets
Dermatoscopy devices
All dermatoscopes can also be used for trichoscopy. However, optimal evaluation of scalp vascular patterns requires a magnification greater than ×20. Images can be acquired by attaching the dermatoscope (Dermlite, 3 Gen LLC, San Juan Capistrano, CA) to a digital camera, which also allows for the zooming of the images.6, 7 Special dermatoscopes that attach to the iPhone (Apple, Cupertino, CA) have been developed by FotoFinder Systems (Handyscope, Bad Birnbach, Germany) and Canfield (DermScope,
Normal scalp
There are only 3 studies on dermatoscopy of the normal scalp, all in Caucasians.10, 12, 13 In the healthy scalp there are evenly spaced groups of few hair shafts coming out of the same follicular ostium. Rakowska et al12 reported that the temporal scalp had mostly single- and double-hair units and the occipital scalp, triple-hair units. The mean hair thickness was 0.061 ± 0.008 mm in the frontal versus 0.058 ±.007 mm in the occipital scalp.
Normal scalp vessels include interfollicular simple red
Seborrheic dermatitis and psoriasis
Dermatoscopy is very useful to distinguish scalp seborrheic dermatitis form scalp psoriasis based on the vascular pattern.10, 18
The vascular pattern of psoriasis is characterized by twisted loops (100% of the cases)10 (Fig 1). Kim et al19 recently evaluated with dermatoscopy 55 patients with scalp psoriasis and 41 patients with seborrheic dermatitis. They concluded that vascular patterns allow distinguishing the two conditions. In psoriasis they describe red dots and globules (most common in
Androgenetic alopecia
Dermatoscopy of androgenetic alopecia (AGA) is characterized by hair diameter variability greater than 20%, which is a very important distinguishing feature.27 Recently, in analogy to anisocytosis in hematology, the term “anisotrichosis” has been proposed to describe diversity of hair shaft diameter observed in AGA.28 Hair shaft variability can also be observed in patches of alopecia areata (AA). However, in AA dermatoscopy shows uniform miniaturization instead of hair shafts with different
Scarring alopecia
Dermatoscopy of both primary and secondary types of scarring alopecia is characterized by decreased hair density and loss of follicular openings. This is easily appreciated in nonpigmented scalp but not in the dark scalp, where both follicular openings and acrosyringeal openings appear as white dots (Fig 5). The only exception is discoid lupus erythematosus (DLE) where white dots disappear because the inflammation also affects the adnexal structures.
Congenital triangular alopecia
Dermatoscopy is a helpful tool to recognize congenital triangular alopecia in atypical locations. Dermoscopic features show absence of terminal hairs and presence of long thin vellus hair.56
Aplasia cutis congenita
Dermatoscopy was helpful to distinguish aplasia cutis congenita from sebaceous nevus, which are the two most common differential diagnoses of congenital patchy alopecia in early infancy.57 In sebaceous nevus, dermatoscopy showed the presence of sebaceous glands that appeared as bright yellow dots not
Conclusion
The literature and our personal experience indicate that dermatoscopy and videodermatoscopy are very useful to differentiate nonscarring from scarring alopecia, diagnose early AGA, distinguish AA from other patchy alopecia, and provide fast diagnosis of tinea capitis. Trichoscopy is a noninvasive technique that does not require expensive instruments and is very well accepted by patients. It definitely improves the quality of care of patients with alopecia and reduces the necessity of taking
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2023, Journal of the American Academy of DermatologyScarring Alopecia
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Funding sources: None.
Conflicts of interest: None declared.