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Section 32: Disorders of the Nail Apparatus

NORMAL NAIL APPARATUS

  • The nail apparatus is made up of:

    • Nail plate, proximal and lateral nail folds, nail matrix, nail bed, and hyponychium.

COMPONENTS OF THE NORMAL NAIL APPARATUS

(see Fig. 32-1)

FIGURE 32-1

Schematic drawing of normal nail.

A diagram depicts the structures of the nail apparatus.
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LOCAL DISORDERS OF NAIL APPARATUS

ACUTE PARONYCHIA

BACTERIAL

PARONYCHIA ICD-10: L03.0

  • Nail fold inflammation.

  • Acute: Bacterial

    • Staphylococcus > Streptococcus, Escherichia coli.

    • Often occurs after a minor trauma.

    • Nail fold is erythematous, swollen and warm, can also have visible pus.

    • Treat with incision and drainage, antibiotics (dicloxacillin, cephalexin, clindamycin, trimethoprim/sulfamethoxazole).

  • Chronic: inflammatory (Fig. 32-2)

    • Associated with damage to the cuticle, mechanical or chemical.

    • Candida, trauma, wet exposure, medications (targeted chemotherapy, retinoids, indinavir).

    • Nail fold is erythematous, sometimes scaly and sensitive, with mild swelling and an absent hyponychium (cuticle).

    • Treat by avoiding irritants, manipulation and excessive water exposure. Topical and/or intralesional steroids, consider topical antifungal if suspected infection.

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.

A patient with chronic paronychia exhibits red scaly skin on the fingertips, blue, swollen proximal nail folds, and vertical ridges in the nail plate.
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ONYCHOLYSIS ICD-10: L60.1

  • Lifting of the nail plate from the nail bed (Fig. 32-3).

  • Etiology

    • Inflammatory: Psoriasis (Fig. 32-3), contact dermatitis, photodrug reaction (doxycycline, fluoroquinolones, griseofulvin, voriconazole).

    • Infection (Candida).

    • Trauma.

    • Nail bed tumors.

  • Can become secondary infected with P. aeruginosa, causing a brown or greenish discoloration (Fig. 32-4).

  • Management: For inflammatory causes, can treat with topical steroid solution (apply under nail) or intralesional steroids. Can also consider systemic therapies for psoriatic onychloysis. Prescribe antifungals for onycholysis secondary to a yeast infection.

FIGURE 32-3

Onycholysis A 60-year-old female with distal onycholysis of fingernails, mild chronic paronychia, and loss of cuticle. Psoriasis is the likely underlying problem.

A patient with onycholysis exhibits dry, scaly, pale yellow nail plates, which appear detached from the nail bed at the distal end. The cuticles are absent.
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FIGURE 32-4

Onycholysis with Pseudomonas colonization (A) Psoriasis has resulted in distal onycholysis of the thumbnail. (B) Infection with Pseudomonas aeruginosa has produced the green-black discoloration of the undersurface of the onycholytic nail.

Two examples of the clinical appearance of onycholysis with Pseudomonas colonization.
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ONYCHAUXIS AND ONYCHOGRYPHOSIS

  • Onychauxis: Thickening of entire nail plate. Can be seen with trauma, older age, psoriasis, and fungal infection.

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