Onychoscopy.

Dermatoscopy can be used to evaluate the nail apparatus (ie, onychoscopy), and it is helpful for the diagnosis of numerous nail diseases and tumors. This article reviews the information that can be obtained in cases of nail dyschromia and especially in cases of melanonychia, in which the distinction between benign melanocytic activation or proliferation and malignancy is crucial. Dermatoscopic changes that accompany specific nail diseases are also reviewed, such as those observed with subungual hemorrhage, bacterial and fungal nail infections, psoriasis of the nail, lichen planus of the nail, and vascular abnormalities of the nail fold.