Nails

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chapter 35 Nails

INTRODUCTION AND OVERVIEW

Nails are important for adornment. Smooth, lustrous nails are considered a sign of health and beauty. The rapid growth of nail salons demonstrates the value that women in particular assign to their nails. Fingernails are also important for fine touch and manipulation. Toenails are protective, especially the large toenails, which bear the brunt of force from jogging, footballing and many other sports.

The nail sits right on the bone of the terminal phalanx, and is closely associated with the distal interphalangeal joint. Toenails especially are prone to repeated microtrauma over the years from footwear, sporting injuries and changes due to arthritis. Fingernails suffer from whatever traumas we put our hands through—chemicals, soaps and detergents and, for some, the added insults of nail salons cutting and dissolving cuticles, using harsh chemicals to apply and remove polishes, false nails, acrylics and so on.

NORMAL NAIL STRUCTURE

The normal nail structure consists of the nail matrix, the nail bed, the proximal and lateral nail folds, the cuticle and the nail plate (Fig 35.1). The nail matrix is made up of the germinative epithelium, and is protected from the environment by the waterproof seal created by the cuticle.

FIGURE 35.1 Diagrammatic drawing of an adult fingertip, showing nail structures through a longitudinal midline plane.

The integrity of the nail depends on the close adhesion of the nail bed and the nail plate, as well as an intact cuticle. The nail bed is closely apposed to the distal phalanx, so changes in the bone and joint will affect the nail.

COMMON NAIL PROBLEMS

HYPERTROPHY AND SUBUNGUAL HYPERKERATOSIS

A number of conditions can cause this problem. Fungal infection, psoriasis and trauma are the most common causes, and may coexist. Fungal infection and trauma are most often seen in toenails; it is rare to have fungal disease in fingernails unless all the toenails are involved too.

Onychomycosis (fungal infection)

Onychomycosis is a relatively common nail disease. A recent European study (Achilles) of 90,000 people aged over 60 years in 16 countries estimated that half had a ‘fungal foot infection’ and that one-quarter of these had onychomycosis.^1,² An Australian study of the general population stated the prevalence as 2–8%, but this figure increases with age.³ An Australian nursing home study put the rate at 22%.⁴

Causes

Most cases of onychomycosis are due to dermatophytes, with Trichophyton rubrum and T. mentagrophytes var. interdigitale being the most common. They usually affect nails by the distal and lateral subungual route. Repeated microtrauma is a common predisposing factor, and tinea between the toes is often present too.

White superficial onychomycosis and proximal subungual onychomycosis may also occur but are less common.

Diagnosis

A diagnosis of onychomycosis should be made before embarking on treatment. Many diseases mimic onychomycosis. Unfortunately, using fungal microscopy and culture, a negative result is obtained in about 40% of cases where infection is truly present. Ideally, when sending a specimen for micro and culture, plenty of the subungual material should be collected and ground up before plating. Distal nail biopsy gives a much higher yield of positive results. Basically this involves cutting off as large a specimen as possible of distal nail (in fact the patient often does this best, and you must stop the nail clipping being lost over on the other side of the room). The piece is sent for histopathology as well as micro and culture, and the pathologist looks for hyphae in the nail plate.

Treatment

One option is to have no treatment apart from regular nail clipping. Oral therapy is usually necessary to cure infections in the nail plate. Other treatment options are:

1. Terbinafine (Lamisil®)—at present the treatment of choice for onychomycosis due to dermatophytes.

The usual dose is 250 mg daily. It comes as 42 tablets and one repeat. In nail clinics patients are often asked to take the second 42 tablets twice a week; this prolongs the therapy and still gives a reasonable dose in the nail plate.

It is important to stress to patients that the infected toenails will need to grow out, and this can take up to a year.

Side effects are normally minimal, but there are some worrying reports of agranulocytosis occurring after a month of therapy. Liver function abnormalities have been reported too. A white cell count and liver function test after a month of treatment are recommended.

2. Itraconazole (Sporanox®)—also highly effective, often given as ‘pulse therapy’. Two tablets twice daily (400 mg) are given for the first week of the month, each month, for 3 months of therapy.

3. Fluconazole—weekly oral fluconazole 150 mg for 3 months is used extensively in many countries.

4. Griseofulvin—500 mg, two tablets per day is usually required to achieve sufficient dosage in the nail. As this drug is only fungistatic, prolonged treatment of up to 2 years may be needed for toenails, especially in the elderly. Even so, the cure rate is around 50% and relapse is common. Nausea and headaches may occur, and liver function tests should be monitored with long-term therapy.

5. Ketoconazole—can be effective but is inadvisable because of potential liver toxicity.

6. Topical therapy—for white superficial onychomycosis or limited disease, topical treatment can be useful, especially in conjunction with removal of diseased nail. Amorolfine (Loceryl®) is the most effective agent currently available in Australia. It is a paint applied weekly after rubbing the nail plate with a file.

7. Physical treatment—nail removal, surgically or with 40% urea paste, can be helpful, especially in single nail disease. It is usually advisable to use topical or oral antifungal treatment as well, or the disease may re-occur.

Psoriasis

Involvement of the fingernails and toenails with psoriasis has been reported in up to 50% of psoriasis sufferers.⁵ The fingernails are more commonly involved than the toenails.

Pitting and onycholysis are common presentations of nail psoriasis, but the more disfiguring abnormality of hypertrophy and subungual hyperkeratosis is the most distressing. Often all the nails eventually become involved, whereas this is less common in onychomycosis. Fingernails are frequently involved and this appearance upsets patients more than that of their toenails, which can be hidden.

Another difference between onychomycosis and psoriasis is that the nails affected by psoriasis often change; some may recover spontaneously but this does not occur in onychomycosis.

Diagnosis

Distal nail biopsy, as described above, is useful. The pathologist looks for parakeratosis on the nail plate.

Treatment

No treatment is fully effective in all people, and often the patient opts for no treatment.

The following can be used.

1. Topical calcipitriol.

2. Intralesional steroids—Kenacort®-A10 (triamcinolone acetonide), diluted in Xylocaine® (lignocaine), injected into the proximal nail fold and/or nail bed can give several months of remission.

3. PUVA (psoralen plus exposure to ultraviolet A)—topical or oral psoralens with UVA sometimes helps.

4. Oral methotrexate—seldom used for nails alone, but if there is widespread skin involvement or arthritis as well, it can be useful.

5. Oral acitretin—again, seldom used for nails alone, but can be useful for severe hyperkeratosis.

An alternative approach is of a cosmetic nature. Preformed artificial nails or sculptured artificial nails may be applied if there is enough keratin for adherence. Nail abrasion, usually done by podiatrists, can also help with appearance, and in reducing discomfort from footwear.

Trauma

Trauma, especially to the toenails, is one of the most common causes of nail dystrophy. Repeated microtrauma is particularly common, from shoes and sports, especially jogging, netball and football. Changes to underlying bones and joints with arthritis and ageing can exaggerate the effects of trauma.

Onychogryphosis

Onychogryphosis is most common in the big toenails. The nail plate is thickened and opaque and the nail bed is hyperplastic. In the extreme form the nail looks like a ram’s horn. In older patients this is due to biomechanical factors and footwear, and secondary foot anomalies such as hallux valgus are commonly associated.

Pincer nails

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