1. MORPHOLOGIC NAIL ABNORMALITIES
Acquired nail disorders may be classified as local or associated with systemic or generalized skin diseases.
Onycholysis (distal separation of the nail plate from the nail bed, usually of the fingers) is caused by excessive exposure to water, soaps, detergents, alkalies, and industrial cleaning agents. Candidal infection of the nail folds and subungual area, nail hardeners, drug-induced photosensitivity, hyperthyroidism, hypothyroidism, and psoriasis may cause onycholysis.
Distortion of the nail, including nail splitting, occurs as a result of chronic inflammation or infiltration of the nail matrix underlying the eponychial fold. Such changes may be caused by impingement on the nail matrix by inflammatory diseases (eg, psoriasis, lichen planus, eczema), warts, tumors, or cysts.
Discoloration and crumbly thickened nails are noted in dermatophyte infection and psoriasis.
Allergic reactions (to resins in undercoats and polishes or to nail glues) are characterized by onycholysis or by grossly distorted, hypertrophic, and misshapen nails.
Paronychia is inflammation of the lateral or proximal nail folds. Acute paronychia presents as a painful erythematous papulonodule or frank abscess of the nail fold and is most commonly due to infection with S aureus (Figure 6–41, eFigure 6–113, eFigure 6–114). Chronic paronychia is most often caused by irritation from water or chemicals with resultant inflammation and possible Candida superinfection.
Acute paronychia. (Used, with permission, from E.J. Mayeaux Jr, MD, in Usatine RP, Smith MA, Mayeaux EJ Jr, Chumley HS. The Color Atlas and Synopsis of Family Medicine, 3rd ed. McGraw-Hill, 2019.)
Cross-sectional view of the anatomy of the distal phalanx, showing the location of a paronychia. (Reproduced, with permission, from Chesnutt MS et al. Office & Bedside Procedures. Originally published by Appleton & Lange. Copyright © 1992 by The McGraw-Hill Companies, Inc.)
Incision of a paronychia. (Reproduced, with permission, from Chesnutt MS et al. Office & Bedside Procedures. Originally published by Appleton & Lange. Copyright © 1992 by The McGraw-Hill Companies, Inc.)
B. Nail Changes Associated with Systemic or Generalized Skin Diseases
Beau lines (transverse furrows) affect all nails and classically develop after a serious systemic illness (eFigure 6–115).
Atrophy of the nails may be related to trauma or to vascular or neurologic disease.
Clubbed fingers may be due to the prolonged hypoxemia associated with cardiopulmonary disorders (Figure 6–42) (eFigure 6–116) (see Chapter 9).
Spoon nails may be seen in anemic patients.
Stippling or pitting of the nails is seen in psoriasis, alopecia areata, and hand eczema (Figure 6–8) (eFigure 6–22...