Leukonychias

White discolorations of the nails are frequent changes. Mostly they are conditioned by traumatic injuries, but many other causes including hereditary diseases, different skin diseases, systemic diseases, and intoxications and exogenous influences can induce complete or partial whitening of the nail. For the diagnostic purpose of these signs, it is necessary to differentiate between leukonychias caused by alteration of the nail plate and conditions caused by modification of the subungeal tissue. Beyond this, the appearance of whitening--total, subtotal, punctuated, striated--has to be considered. For practical identification, the different forms of leukonychias are discussed according to their clinical picture.