Usefulness of high-frequency ultrasonography in the assessment of alopecia areata – comparison of ultrasound images with trichoscopic images

Introduction
Trichoscopy allows us to distinguish between different types of alopecia and to determine the stage of the disease. High-frequency ultrasonography (HF-USG) enables the evaluation of structures that are not available for clinical and trichoscopic examination, but it has not been widely used to date in the evaluation of patients with alopecia areata (AA) and other scalp disorders. Aim: To characterise the ultrasound images of patients with AA, including different stages of the disease, and to compare them with trichoscopic images and other scalp diseases.

Material and methods
Twenty-five patients with AA, on the basis of trichoscopic examination, were qualified to three groups: with active, inactive, and regrowth phase. Next, HF-USG (20 MHz) with qualitative and quantitative evaluation of various elements of the images was performed: entrance echo (EE), dermis (dermal background; DB), follicular structures (FS), dermal/ subdermal border (D/SB). The results were compared with 10 healthy volunteers, 10 patients with androgenic alopecia (AGA), and 12 with seborrhoeic dermatitis (SebD).

Results
Active AA was characterised by FS with distinct borders, drop-like shaped, with a widened distal end located in the lower layers of DB. Inactive AA was characterised by a smaller number of FS without distinct borders. In the regrowth phase, FS of different widths, elongated, and with widened distal parts located at different DB depths were observed.

Conclusions
HF-USG (20 MHz) may be a valuable diagnostic method in patients with AA. Ultrasound images of AA vary according to the stage of the disease and in comparison with AGA, SebD, and healthy individuals.