Evaluation of nail lines: Color and shape hold clues.

Nail lines are a common presenting finding. A thorough inspection of the fingernails and toenails is an integral part of the complete physical examination. An understanding of basic nail anatomy and familiarity with several basic types of nail line enable the clinician to diagnose and treat nail disorders and to recognize underlying systemic diseases, as each type of nail line has a particular differential diagnosis. The authors review leukonychia striata (white lines), longitudinal melanonychia (brown-black lines), longitudinal erythronychia (red lines), and nail-plate grooves (Beau lines).