Nail disorders as clues to systemic disease.

Disorders of the nail unit can provide important clues to underlying systemic diseases. Onychodystrophy or nail abnormalities include altered nail color, shape, or texture with morphology and growth patterns often related to local anatomic factors such as edema, vascular supply, and neurologic innervation. Associated pain or loss-of-function can also affect daily activities. Because nail changes may be due to a range of systemic diseases, the authors provide a systems-based broad overview of the common nail findings in patients with internal disease.