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Nail Disorders

»	What functions do nails serve?
»	Why are nails important in medicine?
»	Do any systemic diseases have specific nail findings?
»	What are Beau’s lines? How are they formed?
»	What is a splinter hemorrhage?
»	Are splinter hemorrhages always associated with subacute bacterial endocarditis?
»	What is the difference between Mees’ lines and Muehrcke’s lines?
»	What are “half-and-half” nails, and with what internal disease are they associated?
»	What is nail fold capillaroscopy? How is it useful?
»	What is clubbing?
»	How is hypertrophic osteoarthropathy related to clubbing?
»	What is the yellow nail syndrome?
»	Are there any characteristic nail changes in primarily dermatologic diseases?
»	What are nail pits?
»	Are there any differences between the nail pits of psoriasis and alopecia areata?
»	What other nail findings are seen in psoriasis? What is the significance of nail changes?
»	How does a pterygium differ from pterygium inversus unguium?
»	What is the most common cause and sequela of a subungual hematoma? How is it treated?
»	Do malignant melanomas occur in the nails?
»	How do you tell the difference between a subungual hematoma and a malignant melanoma?
»	What nail changes are considered peculiar to human immunodeficiency virus (HIV) infection?
»	What is onychocryptosis? Why does it occur?
»	What is a paronychia?
»	Which infectious organisms cause paronychia?
»	How do you treat an acute paronychia?
»	What is the most common cause of green nails?
»	What is the difference between onychomycosis and tinea unguium? What organisms most commonly cause tinea unguium? Where does the infection typically start?
»	List the antifungal medications most often used in the treatment of toenail onychomycosis.
»	What should patients expect when undergoing treatment of onychomycosis?
»	What is “habit tic” disorder? How is it different from median nail dystrophy?
»	List the common benign “tumors” that occur in and around the nail unit.
»	What is an exostosis?
»	Name the four most common malignant tumors of the nail unit.

What are “half-and-half” nails, and with what internal disease are they associated?

Fig. 68.1 Half-and-half nails in a patient with chronic renal disease. (Courtesy of the Fitzsimons Army Medical Center teaching files.)

Half-and-half nails are characterized by apparent leukonychia (white color that disappears with pressure) that affects the proximal half of the nail (Fig. 68-1). Although it may be seen in normal individuals, it is associated with patients with chronic renal disease in approximately 10% of patients.