Nail lichen planus is an inflammatory disorder of the nails with potential for significant cosmetic disfigurement and functional impairment. Nail manifestations may be isolated or appear concurrently with other forms of lichen planus. Longitudinal ridging is the most common clinical finding, but progressive disease may result in irreversible scarring (dorsal pterygium) or permanent nail loss (anonychia). Data on treatment are limited to retrospective studies and case reports. The mainstays of treatment are intralesional and intramuscular corticosteroid injections and oral retinoids. There is a need for randomized controlled trials on nail lichen planus to more rigorously assess efficacy and outcomes.

Trachyonychia is a disorder of the nail unit that most commonly presents with rough, longitudinally ridged nails (opaque trachyonychia) or less frequently, uniform, opalescent nails with pits (shiny trachyonychia). The term trachyonychia refers to \'rough nails.\' This article comprehensively reviews the clinical, histologic, and therapeutic aspects of trachyonychia. The authors\' preferred evaluation and management strategies of trachyonychia are included.

OBJECTIVE: The term trachyonychia, also known as twenty-nail dystrophy, is used to describe thin, brittle nails with excessive longitudinal ridging. The term twenty-nail dystrophy has been incorrectly applied to other conditions that can affect all twenty nails. Therefore, we have conducted a comprehensive review of the clinical features of trachyonychia and have included a discussion regarding the diagnostic accuracy of this condition in the literature.
METHODS: In November and December 2015, we conducted a thorough literature search using the following search terms: \'trachyonychia\', \'twenty nail dystrophy\', and \'sandpaper nails\'. Articles that reported the epidemiology, disease associations, clinical presentation, histopathology, and treatment options for trachyonychia were included. Particular attention was given to case reports to identify misdiagnosed cases of twenty-nail dystrophy.
RESULTS: Our preliminary search yielded 184 results with 72 unique articles ultimately selected for review. Excluded articles included 27 articles in languages other than English, 18 commentaries or reviews, and 67 irrelevant articles. Twelve additional articles described nail abnormalities clinically different from trachyonychia.
CONCLUSIONS: Many other conditions can cause widespread nail dystrophy. The specific characteristics of trachyonychia need to be considered to make the diagnosis of twenty-nail dystrophy.