Are there any characteristic nail changes in primarily dermatologic diseases?

Unfortunately, because the nail unit has only limited ways of responding to pathologic insults, pathognomonic changes are seldom encountered. However, examination of the nails is imperative because there are certain changes that, viewed in context with the entire clinical picture, can help establish a diagnosis (Table 68-2).

Rich P: Nail disorders: diagnosis and treatment of infectious, inflammatory, and neoplastic nail conditions, Med Clin North Am 82:1171–1182, 1998.

Table 68-2. Dermatologic Disorders with Nail Changes
	DISEASE		INCIDENCE		FINDINGS
	Psoriasis		10%–50%		Pits, “oil spots”
	Alopecia areata		20%–50%		Pits
	Lichen planus		10%		Pterygium
	Scleroderma Darier’s disease		Frequent High		Pterygium inversus unguium Wedge shaped, hyperkeratosis
	Pityriasis rubra pilaris		Majority		Yellow-brown, hyperkeratotic