New tools in nail disorders.

Tumors of the nail unit may be difficult to diagnose because of the screening effect of the nail plate. In longitudinal melanonychia, several new promising techniques assist with early diagnosis of melanoma (in vivo matrix dermoscopy and immunohistochemistry) as well as sparing as much of the healthy tissues as is possible (shave biopsy technique). Diagnosing nail disorders is in some instances difficult both for the clinician and the pathologist. New tools such as polymerase chain reaction have been proposed for onychomycosis, which accounts for more than half of nail conditions, will allow quick and accurate diagnosis. However, polymerase chain reaction analysis remains expensive and is not routinely used by clinicians. Scoring nail dystrophy by clinical observation remains very subjective; therefore, severity indexes have been proposed. Another emerging noninvasive technique is forensic analysis of nail clippings for detection of drug intake and abuse, as well as exposure to environmental pollution.