Evaluation of pigmented lesions of the nail unit.

Acquired pigmentary changes of the nail are secondary to a number of etiologies. These include nail matrix nevi; physical induction secondary to trauma; malignant melanoma; nutritional deficiencies; inflammation secondary to lichen planus; endocrine causes such as Addison's disease; or secondary to bacterial, fungal, or viral infections. The most important task faced by clinicians is to distinguish benign from malignant etiologies of nail pigmentation. We will briefly review the various entities that can yield dyspigmentation and their differentiation from melanoma of the nail.