Trichoscopy and LC-OCT findings in sonidegib-induced alopecia in patients with advanced basal cell carcinoma.

Sonidegib is a Hedgehog pathway inhibitor (HHI) used as a first-line systemic treatment for patients with advanced basal cell carcinoma (aBCC). Alopecia is reported as a frequent adverse event (AE), occurring in 49% of patients. Forty-five patients with aBCC were treated with sonidegib between December 2022 and December 2023; among them, 11/45 patients developed alopecia. Trichoscopic features included yellow dots, black dots, exclamation mark hairs, and broken hairs. Upon LC-OCT examination, yellow dots were seen as dilated follicular dark spaces containing malted, nonhomogeneous material and outlined by bright collarets. Black dots corresponded to normal-sized follicular ostia filled with bright, homogeneous material and cadaverized hair. Exclamation mark hairs were short, dark dysmorphic hairs with different sizes of proximal and distal ends, and broken hairs were short dysmorphic hairs. LC-OCT may provide additional insights into early signs and clinical evolution of sonidegib-induced alopecia in patients with aBCC.