SECTION 32: DISORDERS OF THE NAIL APPARATUS

NORMAL NAIL APPARATUS

• 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.

COMPONENTS OF THE NORMAL NAIL APPARATUS

LOCAL DISORDERS OF NAIL APPARATUS

CHRONIC PARONYCHIA ICD-10: L03.0

• 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.

ONYCHOLYSIS ICD-10: L60.1

• 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 ...