Nail and Skin Disorders of the Foot and Ankle
Perla Lansang, MD, FRCPC
Edward Lansang, MD, FRCSC
Johnny Lau, MD, MSc, FRCSC
Dr. Perla Lansang or an immediate family member is a member of a speakers’ bureau or has made paid presentations on behalf of Abbott, Amgen Company, Bausch Pharma, Celgene, Eli Lilly, Johnson & Johnson, and Norvartis. Dr. Lau or an immediate family member has received royalties from Zimmer; is a member of a speakers’ bureau or has made paid presentations on behalf of Bioventus; and has received nonincome support (such as equipment or services), commercially derived honoraria, or other non-research-related funding (such as paid travel) from Integra and Stryker. Neither Dr. Edward Lansang nor any immediate family member has received anything of value from or has stock or stock options held in a commercial company or institution related directly or indirectly to the subject of this chapter.
ABSTRACT
Diseases of the skin and nails of the foot can greatly affect quality of life and can lead to significant morbidity, and rarely, mortality. These diseases can range from traumatic, infectious, inflammatory to neoplastic processes. Traumatic conditions include subungual hematomas and tache noir. Infections, including viral, bacterial, and fungal, are common, and treatment of these conditions is dependent on proper diagnosis and proper choice of anti-infective options. For fungal infections of the nails and feet, some topical treatment options are effective, but for more severe cases, especially for onychomycosis, oral therapy remains to be the most effective option. Inflammatory diseases of the skin and nails of the feet include psoriasis, dermatitis, and lichen planus. These conditions can be treated with topical steroids, but more severe involvement may warrant further work-up and systemic therapy. Melanoma of the acral skin and subungual melanomas tend to have a poorer prognosis because of several factors, delayed diagnosis being of one them. Inspection of the skin and nails of the feet may lead to earlier diagnosis and treatment of these malignancies.
Introduction
Nail and skin diseases of the foot and ankle represent a heterogeneous group of disorders, ranging from tumors to inflammatory conditions to infections. They may have a significant effect on the quality of life of patients; some tumors, such as melanoma, may even be life-threatening. This chapter reviews important diseases of the skin and nails of the foot.
Nail Disorders
Nail Anatomy
The five distinct anatomic regions of the nail apparatus are the nail plate, the proximal nail fold, the nail matrix, the nail bed, and the hyponychium. The nail plate is a fully cornified structure composed of tightly layered keratinized cells generated by the nail matrix. The proximal third of the nail plate is covered by the proximal nail fold, the tip of which forms the cuticle. The nail matrix also is part of the proximal nail fold. The visible white half-moon-shaped area of the nail, called the lunula, corresponds to the distal portion of the nail matrix. The nail bed begins where the lunula ends, and it underlies the entire nail plate. The hyponychium connects the nail bed to the epithelium of the fingertip.1 Morphologic terms related to nail disorders are outlined in Table 1.
Traumatic Subungual Hematoma
Subungual hematoma occurs when a traumatic injury leads to accumulation of blood between the nail plate and the nail bed. Compression of the nail matrix may cause secondary nail dystrophy. The color of a subungual hematoma can range from purple red to black. The possibility of a subungual melanoma should be considered in the diagnosis. Because nail bed lacerations and fractures of the distal phalanx are associated with subungual hematomas, a radiograph should be obtained. It may be necessary to evacuate a large hematoma by creating a hole through the nail plate. A nail bed laceration with a distal phalangeal fracture should be treated with irrigation, débridement, and antibiotics.2
The nail bed can be repaired after thorough cleansing and assessment using loupe magnification. The nail plate is removed to allow adequate visualization and repair,
and the repair is done using simple interrupted sutures with an absorbable monofilament (size 5-7).3 Replacing the nail plate after traumatic injury was found to delay healing and increase the risk of infection.4 A fractured distal phalanx can be reduced or stabilized using a fine Kirschner wire or hypodermic needle.3
and the repair is done using simple interrupted sutures with an absorbable monofilament (size 5-7).3 Replacing the nail plate after traumatic injury was found to delay healing and increase the risk of infection.4 A fractured distal phalanx can be reduced or stabilized using a fine Kirschner wire or hypodermic needle.3
TABLE 1 Morphologic Terms Related to Nail Disorders | ||||||||||||||
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Infectious Conditions
Onychomycosis
The term onychomycosis encompasses both dermatophytic and nondermatophytic infections of the nail. Dermatophytic nail infection is more specifically called tinea unguium and often is associated with tinea pedis. Trichophyton rubrum is the most common pathogen, but Trichophyton mentagrophytes and Epidermophyton floccosum also are common. The infection appears as subungual hyperkeratosis, thickening of the nail plate, and onycholysis (Figure 1).
The diagnosis of onychomycosis involves potassium hydroxide preparation and examination of nail scrapings and fungal cultures to identify the pathogen. Specimens are best taken by clipping part of the affected nail for laboratory microscopic examination and culture.
The use of an oral antifungal agent such as itraconazole, fluconazole, or terbinafine provides a cure rate as high as 80%, but recurrent disease is common. Liver toxicity and drug interaction, especially with the azoles, must be considered when a systemic antifungal agent is used.5 The treatment of choice for onychomycosis is oral terbinafine. In clinical studies, terbinafine was found to be more effective for treatment than azoles such as itraconazole and fluconazole.6,7,8,9 Oral therapeutic options for toenail onychomycosis are listed in Table 2. Surgical avulsion with topical therapy can be considered, especially for single nail involvement, but a low response rate and a high recurrence rate were reported when this treatment modality was used.10
 FIGURE 1 Photograph showing toenail onychomycosis. In this patient, fungal culture identified Trichophyton rubrum as the pathogen. (Courtesy of Scott Walsh, MD, Toronto, Ontario, Canada.) |
Topical antifungal therapy for limited onychomycosis has become available in the past few years. Efinaconazole has been shown to be superior to placebo in randomized controlled trials.11 Tavaborole is another topical agent that is available for the treatment of onychomycosis.12 Topical therapy is a suitable option for patients who have limited disease or have comorbidities that preclude the use of systemic antifungals.
Paronychia
Acute paronychia appears as redness, swelling, and pain of the periungual area. The most common cause of acute paronychia is Staphylococcus aureus. The infection may be secondary to trauma or toenail ingrowth. Recurrence of acute paronychia should raise suspicion of a herpes simplex infection. The treatment of acute paronychia depends on the causative agent,
and culturing is necessary to identify the agent. Incision and drainage can relieve pain if there is a local collection of pus.
and culturing is necessary to identify the agent. Incision and drainage can relieve pain if there is a local collection of pus.
TABLE 2 Oral Drugs for Treating Toenail Onychomycosis | |||||||||
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Chronic paronychia is characterized by redness and swelling of the proximal nail fold. There is much less pain than in acute paronychia, and the absence of the cuticle is a hallmark finding. Candida is a common pathogen. Chronic paronychia is common in workers whose feet are exposed to water and irritants. The treatment consists of avoidance of water and irritants. There is evidence that the use of topical steroids and topical azole antifungal agents is effective.1
Inflammatory Conditions
Psoriasis
Nail involvement is extremely common in psoriasis and may be the only manifestation of the disease. Pitting is the most common finding in nail psoriasis. Onycholysis and the appearance of an oil drop under the nail (the oil drop sign) also are common. Other findings include subungual hyperkeratosis, thickening of the nail plate, and splinter hemorrhages. A diagnosis of nail psoriasis should alert the clinician to search for psoriatic arthritis because there is an association between the two conditions.
Nail psoriasis is difficult to treat. The first-line treatment is with topical steroids and/or calcipotriol. Systemic therapy with methotrexate, cyclosporine, or biologic agents is effective but reserved for patients with moderate to severe skin involvement.13,14,15,16 More recently, clinical trials using biologics for nail psoriasis have been published and systemic therapy for nail psoriasis has been studied, recognizing that this disease has significant impact on function and quality of life.17,18
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