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NAIL INFECTIONS AND PREDISPOSING FACTORS

Predisposing factors for nail and periungual infection

A number of factors may increase the risk of infection in the vicinity of the nail apparatus, or may complicate its diagnosis. Relevant issues include the following.

Most of these conditions are dealt with later in this or in other chapters, but onycholysis is discussed further at this point.

Onycholysis

Separation of the nail plate from the bed is called onycholysis and may be due to a variety of causes (Figs 29.1–29.4 and Table 29.1).

    Look for all the causes given in Table 29.1 and eliminate any (e.g. take off all acrylic nails). If none is found, ask the patient to trim the nail back as far as the onycholysis will allow, to prevent lifting and promote dryness. No cleaning beneath the nail should be performed, as this aggravates the condition.

    Onycholysis is often misdiagnosed as a fungal infection (although there is no nail plate thickening); this incorrect view may unfortunately appear to be confirmed by results of clippings for mycology. However, when fungi are identified in onycholysis, they are simply colonizing the onycholytic space rather than causing nail plate infection (Fig.29.5). Most are opportunistic yeasts or saprophytic molds. Therefore topical therapy is indicated, such as an antiyeast topical solution (in contrast to onychomycosis, where oral antidermatophyte agents are necessary).

    Bacterial infections may also invade the onycholytic space, notably Pseudomonas infection, which causes a greenish black color (see later).

Figure 29.1 Onycholysis. This young woman had long nails and onycholysis of uncertain etiology.

Figure 29.2 Onycholysis from allergic contact dermatitis to artificial nails.

Figure 29.3 Onycholysis from nail-hardening glue.

Figure 29.4 Onycholysis from chronic trauma.

Figure 29.5 Onycholysis with colonization of the subungual space by Candida. Note the brown discoloration that has resulted. Compare this with Figure 29.10, where pseudomonal colonization has caused a green color, and with Figure 29.1, where no discoloration has occurred.

Fungal infections

Onychomycosis is most commonly due to dermatophyte infections (most commonly causing distal and lateral subungual onychomycosis, Figs 29.6–29.8) but may be due to yeasts (e.g. in chronic mucocutaneous candidiasis, Fig. 29.9). The role of yeasts in chronic paronychia is discussed here. Otherwise, fungal infections of the nail are dealt with in Chapter 26.

Figure 29.6 Distal subungual onychomycosis in an older adult.

Figure 29.7 Distal subungual onychomycosis in a 5-year-old. Note how heavily infected nails occur adjacent to totally normal nails. Cutting back the big toe’s nail plate has revealed the friable subungual debris. This material is the most desirable for culture.

Figure 29.8 Distal subungual onychomycosis. Although, most of the time, a culture shows a dermatophyte, a yeast or mold may be grown. This nail grew out Aspergillus.

Figure 29.9 Chronic mucocutaneous candidiasis.

Pseudomonas colonization

Pseudomonas often grows in the moist environment created by an onycholytic nail (onycholysis is a separation of the nail plate from the nail bed and has many causes; it is discussed later). A green or black discoloration of the nail is seen when there is Pseudomonas colonization (Figs 29.10 and 29.11). Note that the nail is not thickened, as would occur in a fungal infection, also that the pigmentation is of the undersurface of the nail rather than of the skin (in melanoma, pigmentation is of the skin and is simply visible through the nail). Rarely, the green color of Pseudomonas may extend on to the skin (Fig. 29.12).

    For treatment, cut the nail as far back as possible. Then have the patient apply gentamicin otic solution twice daily. If this alone is not sufficient, one may try nightly 5-min soaks with either vinegar or hibitane. Following the soak, apply the gentamicin (either ointment or solution). Alternatives are 3% thymol twice a day or ciprofloxacin (500mg orally twice daily for 2 weeks). A fungal infection (candida) may coexist, so combination treatment is often indicated.

Figure 29.10 Colonization of an onycholytic nail by Pseudomonas. Nothing but Pseudomonas creates this green color.

Figure 29.11 Pseudomonas infection of many nails.

Figure 29.12 Pseudomonas of the nail and skin. The green color is secondary to Pseudomonas colonization of the nail. A greenish hue of the tip of the involved toe can also be appreciated.

PRACTICE POINTS

Paronychia, acute

Etiology and pathogenesis

The potential space between the nail apparatus and tissue along the lateral nail fold is a weak area in the body's defenses. Bacterial infection may occur, usually due to Staphylococcus aureus or streptococci. Anaerobes or Candida may also be found.

    Risk factors include trauma, manipulation, and oral isotretinoin treatment. Herpetic whitlow should be excluded.

Clinical

An acutely tender, red, periungual swelling occurs in acute paronychia (Fig.29.13). Pustules may be visible below the cuticle (Figs 29.14 and 29.15). The nail is usually not dystrophic unless the acute infection occurs on a background of chronic paronychia.

Figure 29.13 Acute paronychia. Acutely red, inflamed skin unilaterally about one lateral nail fold is characteristic.

Figure 29.14 Acute paronychia. Often the patient is able to express pus. This pus should be cultured.

Figure 29.15 Acute paronychia. In acute paronychia, pus is often visible through the lateral or proximal nail fold.

Differential diagnosis

This is discussed in Table 29.2.

Treatment

The area should be drained if fluctuant. Always send swabs for culture from any pustule or discharge. Soaking should be prescribed if the area is crusted or already draining. Oral antibiotics should be given.

Paronychia, chronic

Etiology and pathogenesis

The etiology is frequently multifactorial and includes the following.

Clinical

The periungual areas of many nails are swollen, red, and inflamed in chronic paronychia (Fig.29.16). The cuticle is lost, and significant dystrophy of the nail often occurs.

Figure 29.16 Chronic paronychia. The periungual areas are swollen and tender. Repeated flares have caused nail dystrophy.

Differential diagnosis

This is discussed in Table 29.2.

Treatment

Eczema in the periungual area should be treated with a topical steroid, together with allergen avoidance where proven relevant.

    Whatever the cause, the area should be kept meticulously dry, which may require use of gloves or altering hobbies or activities. If wet work is unavoidable, a greasy emollient may give some protection, but prolonged occlusion of the space under the nail fold should be avoided.

    A topical antiyeast solution should be applied twice to three times a day. The topical antiseptic 3% thymol in alcohol, applied twice to three times a day, in addition to the antiyeast medication, has been recommended. If necessary, a combined steroid with an antiyeast agent may be appropriate, the logic being to treat both the inflammation and the secondary yeast colonization that provides an ongoing inflammatory stimulus. Specifically for candidal infection, systemic therapies such as ketoconazole are effective, but no more so than topical treatment, and have both side effect and cost implications.

    Marsupialization has been suggested if more conservative measures fail.

PRACTICE POINTS

Periungual verruca

Periungual warts are common in children. When the wart (or any tumor) presses down on the matrix sufficiently, a groove in the nail results (Fig.29.17).

Figure 29.17 Periungual warts and grooved nail.

White/Cox: Diseases of the Skin, 2ed.(c) 2006, Elsevier Inc. All rights reserved.