Nail Lichen Striatus and Its Differential Diagnoses.

Background: Lichen striatus (LS) is a benign, mostly self-limiting dermatological condition, primarily affecting the skin, and sometimes the nails. It is characterised by the sudden onset of a band-like rash, typically following Blaschko lines. The exact cause of LS is not well established, but it is believed to be an abnormal immune response to the altered keratinocyte clone after a triggering event. Summary: Although nail LS is regarded as rare, it is probably underreported. Single-visualised nail dystrophy, especially partial involvement of the nail, with or without skin rash, should prompt the LS diagnosis among differentials. Onychoscopy might be helpful to better visualise the clinical signs. Nail dystrophy often has a prolonged course even after the resolution of skin lesions. Topical steroids, calcineurin inhibitors, and intralesional steroid injections might be an option for symptomatic patients or for severe and prolonged nail dystrophy. Key Messages: (i) Single nail involvement, nail changes located on one portion of the nail, and the presence of typical linear band-like skin rash should prompt the LS diagnosis. (ii) Onychoscopy might be helpful to better visualise the clinical signs and to avoid unnecessary biopsies. (iii) Nail unit biopsy should be performed if the diagnosis is uncertain to exclude nail involvement of more severe and progressive disease course like nail lichen planus and/or nail unit tumours.