trichoscopic

Trichoscopy, also called trichoscopic examination, is a noninvasive diagnostic technique that uses a dermatoscope to visualize hair shafts, follicles, and scalp skin at magnifications typically from 20x to 70x. Performed in outpatient settings, it can be done with contact or noncontact modes and with polarized or nonpolarized light. Immersion fluids may be used to improve visualization of hair shafts and skin structures.

Indications include evaluation of nonscarring and scarring alopecias, differentiation among causes of hair loss, assessment of hair shaft disorders, and monitoring disease activity or treatment response. Trichoscopy complements clinical history and dermal biopsy when needed, and it can guide biopsy site selection to maximize diagnostic yield.

Characteristic findings are described as patterns or features. In alopecia areata, yellow dots and black dots, short broken hairs, and exclamation mark hairs are commonly observed. Androgenetic alopecia often shows variable hair shaft thickness (anisotrichosis) with perifollicular yellow-brown pigmentation and a reduction in follicular openings. Lichen planopilaris and other cicatricial alopecias may display perifollicular erythema, blue-gray perifollicular dots, and perifollicular scaling. Tinea capitis can present with comma hairs and corkscrew hairs. Trichotillomania may show hairs of different lengths, irregular frayed ends, and flame hairs. Additional findings include pili torti, pigtail hairs, and hair shaft abnormalities.

Limitations include operator dependence, variability in equipment, and overlapping patterns between conditions. Trichoscopy should be interpreted in the broader clinical context, and histopathology remains definitive in uncertain cases.