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  • The nail apparatus is made up of:

    • Nail plate, the horny "dead" product.

    • Four specialized epithelia: Proximal nail fold, nail matrix, nail bed, and hyponychium.




  • Associated with damage to the cuticle, mechanical or chemical (See Fig. 32-1).

  • At risk: Adult women, food handlers, and house cleaners.

  • Chronic dermatitis of proximal nail fold and matrix: chronic inflammation (eczema, psoriasis) with loss of cuticle, separation of nail plate from proximal nail fold (Fig. 32-2).

  • Predisposing factors:

    • Dermatosis: Psoriasis, dermatitis [atopic, irritant (occupational), allergic contact], and lichen planus.

    • Drugs: oral retinoids (isotretinoin, acitretin), indinavir.

    • Foreign body: Hair, bristle, and wood splinters.

  • Manifestations: First, second, and third fingers of the dominant hand; proximal and lateral nail folds erythematous and swollen; cuticle absent.

  • Secondary infection/colonization: Candida spp., Pseudomonas aeruginosa, or Staphylococcus aureus. Nail plate may become discolored; green undersurface with Pseudomonas. Infection associated with painful acute inflammation.

  • Management:

    • Protection.

    • Treat the dermatitis with glucocorticoid: topical, intralesional triamcinolone, or a short course of prednisone.

    • Treat secondary infection.

Figure 32-1

Schematic drawing of normal nail.

Figure 32-2

Chronic paronychia The distal fingers and periungual skin are red and scaling. The cuticle is absent; a pocket is present, formed as the proximal nail folds separate from the nail plate. The nail plates show trachonychia (rough surface with longitudinal ridging) and onychauxis (apparent nail plate thickening caused by subungual hyperkeratosis of nail bed). The underlying problem is psoriasis. Candida albicans or Staphylococcus aureus can cause space infection in the "pocket" with intermittent erythema and tenderness of the nail fold.


  • Detachment of the nail from its bed at distal and/or lateral attachments (Fig. 32-3).

  • Etiology

    • Primary: Idiopathic (fingernails in women; mechanical or chemical damage); trauma (fingernails, occupational injury; toenails, podiatric abnormalities, poorly fitting shoes).

    • Secondary: Vesiculobullous disorders (contact dermatitis, dyshidrotic eczema, herpes simplex); nail bed hyperkeratosis (onychomycosis, psoriasis, or chronic contact dermatitis); nail bed tumors; drugs.

    • In psoriasis, the yellowish-brown margin is visible between the pink normal nail and white separated areas (Fig. 32-3). In "oil spot" or "salmon-patch" variety, nail plate–nail bed separation may start in the middle of nail.

  • Colonization with P. aeruginosa results in a biofilm on the undersurface of the onycholytic nail plate, causing a brown or greenish discoloration (Fig. 32-4).

  • Other secondary pathogens that can colonize/infect the space are Candida spp., dermatophytes, and numerous environmental fungi.

  • Underlying disorders in fingernail onycholysis: trauma (e.g., splinter), psoriasis, photoonycholysis (e.g., doxycycline), dermatosis adjacent to nail bed (e.g., psoriasis, dermatitis, and chemical exposure), and ...

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