Physical Signs

The key to accurate diagnosis of nail disease is through recognition and classification of clinically apparent alterations to the normal nail unit. Nail signs are classified as changes in both color and shape in the nail fold, matrix, nail bed, hyponychium, and the nail plate. This chapter on physical signs defines the alterations in normal structure and color, findings that can lead the clinician toward the diagnosis of a nail-associated systemic disease or a nail sign of a dermatological condition. An accurate diagnosis requires a discerning eye and a systematic nail examination. Criteria are defined for diagnosing such clinically important nail conditions as clubbing, koilonychia, Beau's lines, and onycholysis – nail conditions that are associated with systemic disease. An appreciation for nail changes associated with dermatological conditions as well as tumors and inflammatory changes in the nail unit begins with careful observation.