Hair flag sign: Macroscopic and trichoscopic feature of hair regrowth in alopecia areata.

Abstract

Souissi et al.1 recently described the trichoscopic flag sign in regrowing hair in alopecia areata (AA). We would like to communicate a case presenting with simultaneous macroscopic and trichoscopic hair flag sign as features of hair regrowth in AA. A healthy 32-year-old man presented with a four-month history of patchy hair loss of the scalp and beard. Clinical examination revealed six oval alopecic lesions with black dots and broken hairs on dermoscopy, findings consistent with AA. He was treated with monthly intralesional triamcinolone acetonide (4 mg/mL). After five months of treatment, he presented a bundle of hairs with alternating horizontal bands of depigmented and normally pigmented hairs (macroscopic flag sign) over the scalp in areas of prior alopecic patches (Fig. 1a). Meticulous evaluation revealed multiple alternating bands in the same hair shaft, finding known as segmental heterochromia2 (Fig. 2a - 2b). Dermoscopy demonstrated black and white horizontal bands in the same hair shaft (Fig. 1b), corresponding to the trichoscopic flag sign.1 Microscopic evaluation showed gradual pigmentation from distal to the proximal segment of the hair shaft (Fig. 2c). The patient had a good nutritional status and denied alcoholism or usage of any systemic medications.