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Nail disorders

Introduction

Nail problems are a frequent source of concern to patients. Tinea unguium and psoriasis account for the vast majority of nail disorders, but there are numerous other causes of nail dystrophies.The nail is important functionally and cosmetically. Fine motor skills such as picking up a pin from a flat surface are impossible without fingernails. The toenails—in particular the great toenails—provide counter-traction when walking and running, and the loss of these nails may lead to pain or an abnormal gait.The nail frequently suffers trauma in day-to-day activities and is also the focus of compulsive behaviours such as nail biting, picking, cleaning and polishing.

Anatomy

The nail apparatus consists of the nail matrix, the nail bed, the proximal and lateral nail folds, the cuticle and the nail plate. The nail matrix contains the germinative epithelium, which is protected from the environment by a waterproof seal created by the cuticle. The structural integrity of the nail unit requires an intact cuticle and solid adhesion between the nail plate and the nail bed. The nail bed is in close apposition to the distal phalanx and the shape of the nail reflects the shape of the underlying bone. The nail bed is thrown into longitudinal folds, much like corrugated iron. The undersurface of the nail plate has similar folds that interdigitate with the nail bed.

Diagnosis

There are only a limited number of ways in which injury, infection, inflammation and neoplasia may present in a nail. See Table 1 for important physical signs, and the main causes of each of these presentations. Some conditions (eg tinea) may present in a variety of ways.

Common nail disorders (Table 1)

Tinea of the nails (onychomycosis, tinea unguium)

Onychomycosis is the term used for fungal infection of the nail. The condition is unsightly and may cause discomfort. Toenails are affected more commonly than fingernails. It is most commonly produced by dermatophyte moulds such as Trichophyton rubrum and Trichophyton mentagrophytes var interdigitale. T. rubrum infections usually also involve the sole of the foot, particularly the areas of thick skin, and frequently produce moccasin tinea pedis. T. rubrum is an anthropophilic fungus—humans are the natural reservoir of infection. Infections are frequently chronic and resistant to therapy. T. mentagrophytes var interdigitale is also an anthropophilic fungus and frequently infects the toe web spaces or the soft parts of the sole of the foot.The first stage of onychomycosis is hyperkeratosis of the undersurface of the distal nail plate and the distal nail bed (hyponychium). This is known as distal subungual onychomycosis (DSO). The fungus seems to travel underneath the nail plate in the longitudinal folds of the nail bed to produce spears of subungual hyperkeratosis. These spears are one of the most useful clues to the diagnosis of onychomycosis. Progressive nail involvement produces total dystrophic onychomycosis (TDO).T. mentagrophytes var interdigitale may also produce an unusual form known as white superficial onychomycosis (WSO). The diagnosis is confirmed by taking scrapings from the nail surface. WSO is responsive to topical imidazoles, whereas DSO and TDO are unresponsive.Because many other disorders can mimic tinea of the nail, it is important to establish a diagnosis of tinea microbiologically before commencing treatment. This is done by first taking clippings of the affected distal nail plate and then scraping any subungual hyperkeratosis.Microscopy and then culture will be positive in approximately 80% of cases of onychomycosis. Nail plate histology can be used if the culture is negative. For histology, a clipping of the distal nail plate is sent to the pathologist in formalin and stained with PAS (periodic acid Schiff reaction) to demonstrate the fungal hyphae. This increases the diagnostic yield in difficult cases.Treatment options must be carefully considered, particularly if treatment is for cosmetic reasons only, as effective drugs are expensive and can have serious adverse drug reactions. However, the toenails can be a reservoir of infection which can precipitate recurrent cellulitis in association with tinea pedis.First-line treatment for all types of nail tinea consists of

Terbinafine has a cure rate of 70% to 80%. Itraconazole and fluconazole have been used extensively overseas and a 3-month course has a cure rate of 60% to 70%. There is limited published data for use of itraconazole or fluconazole for tinea of the nails in children; terbinafine is currently the drug of choice. Prior to the release of terbinafine, ketoconazole and griseofulvin were the main treatments, both of which needed to be taken continuously for 12 to 18 months. Ketoconazole use was limited by the potential complication of severe hepatic toxicity. Griseofulvin is safe but relatively ineffective; it has a cure rate of around 30% after 12 or more months of continuous therapy.Topical nail lacquers are also available over-the-counter in pharmacies for the treatment of onychomycosis. These agents have no effect on TDO, but may have limited efficacy on DSO in patients intolerant of oral antifungals or not wanting to take oral medication for this problem. For superficial or distal nail involvement, use

One difficulty in treating onychomycosis is determining when treatment has failed and a second course is required. At the end of the 3-month treatment period most nails still look abnormal, as a totally dystrophic nail takes up to 9 months to grow out. If normal nail is emerging proximal to the dystrophic nail, a scratch with a scalpel blade should be made at the base of the dystrophy. This scratch can then be followed by the patient until it grows out. If the dystrophic nail is growing out it remains distal to the scratch and no further treatment is required. If the dystrophy moves proximal to the scratch, this indicates ongoing fungal invasion of the nail which requires further treatment.

Psoriasis of the nail Psoriasis of the nail plate may present as pitting, onycholysis (lifting of the nail plate from the nail bed) or subungual hyperkeratosis. Rarely salmon spots may be seen in the nail plate as a manifestation of pustular psoriasis when a pustule forms in the nail bed itself. Psoriasis can closely mimic onychomycosis and it is therefore necessary to exclude tinea by fungal culture or histology before commencing therapy. In psoriasis, nail plate histology may reveal parakeratosis, which is suggestive but not diagnostic of nail plate psoriasis.There is no effective topical therapy for psoriasis of the nails, although potent topical corticosteroids, may be worth trying. Intralesional injections of corticosteroids into the nail apparatus help in some cases but are painful and need to be repeated regularly. Calcipotriol ointment under occlusion has been used for distal onycholysis and subungual hyperkeratosis. Systemic therapy might result in improvement of nails, but it would not usually be indicated for nail disease alone.

Twenty nail dystrophy Twenty nail dystrophy is an uncommon disorder seen in pre-adolescent children. It is characterised by thinning and roughening of all (or almost all) twenty nails. It tends to be self-limiting. It may be a precursor of psoriasis (and precede it by many years), lichen planus or alopecia areata. Management of twenty nail dystrophy is expectant. It tends to spontaneously resolve after 2 to 3 years. No therapy has been reliably shown to hasten resolution.

Onycholysis Onycholysis is a sign rather than a disease per se. It refers to separation of the nail plate from the underlying nail bed. This makes the previously transparent nail plate opaque, as an air interface is introduced between the nail and the nail bed. There are many causes of onycholysis, the most common being psoriasis, tinea and trauma. Other causes include thyrotoxicosis (Plummer’s nails), photosensitivity (especially associated with tetracyclines and thiazide diuretics), warts, tumours, collagen vascular diseases, lichen planus, Reiter’s disease, blistering disorders, exposure to chemicals and solvents, and peripheral vascular disease. Examine the other nails for evidence of psoriasis, ask about a history of psoriasis and inflammatory arthritis and carry out a full cutaneous examination (including the scalp), looking for psoriasis. Examine the interdigital web spaces of the toes for tinea and take distal nail plate clippings to culture for tinea. Ask about a history of trauma and what the patient is inserting beneath the nail to clean out accumulated debris.Treat any associated infection (seen as olive green discolouration on the undersurface of the onycholysis) with

Advise patients to:

· cut the nail short and keep it short

· avoid inserting things beneath the nail to clean out debris

· keep their hands out of water

· use a mild soap and shampoo

· protect the growing nail by covering the nail apparatus with tape. Refer unresponsive cases to a dermatologist.

Lichen planus of the nail Lichen planus of the nail most commonly presents with atrophy of one or more nails. The nail plate appears thin and may be predisposed to splitting and breakage. More advanced disease produces pterygium, whereby the nail matrix is destroyed and the proximal nail folds develop an adhesion to the nail bed. Finally, total loss of the nail may occur. Nail changes may appear in conjunction with skin or mucosal changes of lichen planus (seelichen planus). Lichen planus may be preceded by twenty nail dystrophy.A biopsy of the nail matrix is desirable but not always practicable prior to treatment. The aim of treatment is to prevent scarring in the nail unit that will lead to permanent dystrophy. If the patient is seen before destruction of the nail unit occurs, use intralesional corticosteroids. Use

If multiple nails are affected, consider giving a course of oral corticosteroids. Use

Prednisolone has been reported to induce long-term remissions of nail lichen planus; however, it usually relapses.

Trauma to the nail Trauma to the nail apparatus is a common cause of nail dystrophy. A haematoma in the nail bed or a deformity of the nail plate following a major injury such as jamming a finger in a door is obvious to both patient and doctor; however, a lesser but repetitive injury such as jogging with ill-fitting footwear may cause confusion.Patients with habit tics may present with short nails due to biting, or with horizontal depressions in the nail plate at the same angle as the cuticle due to vigorously pushing back the cuticle. Vigorous cleaning of the undersurface of the nail may produce a purely traumatic onycholysis, or aggravate a psoriatic or fungal onycholysis.Long nails frequently get knocked, and pressure on the undersurface may initiate lifting of the nail plate away from the nail bed. Once a space is created beneath the nail plate, it tends to accumulate moisture and debris; secondary infection is common and can produce discolouration of the nail plate—Pseudomonas and Aspergillus stain the nail plate green. Attempts to clean out this space under the nail plate will extend the onycholysis proximally and further aggravate the condition. The management of onycholysis is discussedelsewhere.The nature of the trauma needs to be identified and any further trauma avoided. Protecting the nail by daily taping with surgical tape can be helpful. Some cases will be amenable to surgical correction, while others will be beyond treatment.

Paronychia

Chronic paronychia

Chronic paronychia is painless and is a traumatic nail dystrophy. Pushing back the cuticles, or removal of the cuticles through keratolytics (as used by manicurists) damages the waterproof seal between the proximal nail fold and the nail plate that protects the nail matrix. Once damaged, water and debris can enter the nail matrix and produce inflammation of the undersurface of the proximal nail fold.Loss of the cuticle is an essential feature of the diagnosis; if the cuticle is intact, consider other causes of swelling of the proximal nail fold. Nail biting is commonly associated. Treatment is dependent on correct care of the cuticle.Secondary infection with Candida is common. Although Candida may aggravate the problem, it does not cause it; paronychia is essentially a problem caused by nail manicure that damages the integrity of the cuticle. Chronic paronychia may be aggravated by episodes of acute paronychia caused by secondary infection with staphylococci. Advise patients to:

· not push back their cuticles or manicure their nails

· avoid playing with or picking at their cuticles

· never insert anything beneath the cuticle to clean out debris

· keep their hands out of water, and wear cotton-lined rubber gloves when doing the dishes or other wet work

· wear cotton gloves in the garden and leather gloves in cold weather

· use a mild soap and shampoo to minimise irritation in the shower

· continue with meticulous hand care until the cuticle regenerates (approximately 6 weeks). Topical corticosteroids are helpful. Use

If there is secondary Candida infection, add

When there is persistent exudate, use an antiseptic tincture to dry out the area:

When the area is dry and without exudate, to waterproof and protect the area, use

Refer unresponsive cases to a dermatologist.

Acute paronychia

Acute paronychia is due to bacterial (usually staphylococcal) or, rarely, viral (herpes simplex virus) infection. It may aggravate chronic paronychia. The proximal nail fold becomes painful and pus should be drained.For staphylococcal infection not responding to drainage, use

For patients hypersensitive to penicillin (excluding immediate hypersensitivity), use

For patients with immediate penicillin hypersensitivity, use

For infection caused by herpes simplex virus (herpetic whitlow), use

Aciclovir is the preferred treatment in children with acute paronychia caused by herpes simplex virus.

Ingrown toenails

Ingrown toenails are one of the most common nail problems seen in general practice. The condition is painful and is usually seen in young adults. The aetiology is frequently multifactorial and includes constitutional and environmental factors. Congenital malalignment of the nail, hereditary overcurvature of the nail and imbalance between the width of the nail matrix and the nail bed are the main predisposing factors, while convex or excessive cutting of the nail, pointed-toe and high-heeled shoes, and onychomycosis are precipitating factors. Occasionally, oral retinoids may also precipitate ingrown nails.An ingrown nail occurs when the corner of the nail pierces or is about to pierce the lateral nail fold epithelium, and the keratinous nail plate and associated debris irritate the lateral nail fold dermis. Improper trimming of the nail may also result in a spicule of nail burrowing under the skin of the lateral nail fold and producing inflammation, much akin to an ingrowing hair.Initially there is slight pain and swelling of the skin of the lateral nail fold. The oedema aggravates the condition by compressing the nail from above and further embedding it into the lateral nail fold. The condition becomes more painful, especially with pressure from footwear, and granulation tissue may form. Discharge of fetid seropurulent exudate may occur from the oedematous lateral nail fold, due to bacterial colonisation. Staphylococcal infection may occur.Finally, epidermis grows over the granulation tissue, making it impossible to elevate the corners of the nail out of the lateral nail folds.Conservative management is indicated initially in all cases and includes treatment of any coexisting bacterial infection with topical antiseptic soaks, such as

Oral antibiotics are rarely required, and in general are used only if there is frank suppuration from the lateral nail fold or cellulitis developing around the toe. Di/flucloxacillin or cephalexin may be used empirically (see acute paronychia); however, the most appropriate antibiotic will be determined by culture and sensitivities.The patient should be advised to cut the distal free edge of the nail in a straight line and not to cut the nail too short.Granulation tissue should be treated with

The nail edge should be gently lifted out of the lateral nail fold and moistened cotton wool (eg soaked in alcohol 60%) packed beneath the nail to maintain elevation of the distal nail plate. The nail should be repacked daily with the maximum amount of cotton wool that can be inserted until the problem is rectified in 7 to 14 days. To increase pliability and facilitate elevation of the corners of the nail plate, the centre of the nail may be filed down until it is quite thin and the pink nail bed shines through.A lacerating spicule of nail may have burrowed into the skin of the lateral nail fold, where it acts as a foreign body. It is important to look for this and remove it. Local anaesthetic may be required for full examination of the area.If epidermis has grown over the granulation tissue in the lateral nail fold, and the nail plate cannot be lifted out of the lateral nail fold, the lateral nail fold should be excised first.Surgical procedures may be used if conservative therapy fails (see Table 2).

Surgical procedures for ingrowing toenails (Table 2)

In general, nail avulsion and destruction of the lateral nail matrix with either segmental phenolisation, cryosurgery or CO2 laser ablation is the favoured treatment if surgery is required. The aim is to reduce the width of the nail by about 20%; the procedure is generally well-tolerated.Dermatitis of the nails Dermatitis may affect the proximal nail folds and produce nail pitting or horizontal depressions (Beau's lines). In contrast to habit tic deformity of the nail, these depressions mirror the lunula rather than the cuticle.To treat, avoid irritants and use

This will usually reverse any associated nail dystrophy.

Nail changes associated with alopecia areata Koilonychia Koilonychia is a relatively common nail dystrophy that is sometimes caused by iron deficiency anaemia. However, most adult cases are idiopathic, and some are due to trauma. Paradoxically, iron overload as seen in haemochromatosis may also produce koilonychia.In cases of iron deficiency, iron replacement therapy usually leads to normalisation of the nail plate contour.Alopecia areata (patchy areas of hair loss) is often associated with pitting of the nails, which is a poor prognostic sign for regrowth of the alopecia (see Hair disorders). Twenty nail dystrophy may occur in prepubescent children as a prodrome to alopecia areata. There is no treatment that has been shown to be effective for the nail changes associated with alopecia areata. The activity of nail disease does not seem to correlate with the activity of the scalp disease.

Half-and-half nails Half-and-half nails, where there is pallor of the proximal half of the nail plate and erythema of the distal half, is a distinctive picture that may be seen in patients with renal, hepatic or cardiac failure. However, many patients with half-and-half nails are well, with no obvious systemic disease. If a systemic illness is identified, treating that illness will lead to resolution of the half-and-half nails.

Myxoid pseudocyst A myxoid pseudocyst may occur when osteoarthritis of the distal interphalangeal joint is associated with leakage of myxoid fluid into the surrounding tissue. This fluid may collect and form a pseudocyst that exerts pressure on the nail matrix and leads to nail plate deformity. The most common site is in the proximal nail fold and pressure on the dorsal surface of the nail matrix may lead to the production of a nail plate with a gutter-like depression.Some pseudocysts resolve spontaneously. If persistent and symptomatic, try

If the pseudocyst persists, refer for surgery. As many pseudocysts are connected to the joint, surgery has a significant failure rate unless the communicating pedicle is identified and tied off.

Nail apparatus melanoma Nail apparatus melanomas are rare but frequently fatal neoplasms. They account for between 1.5% and 3% of all melanomas. All age groups can be affected, although it is most common in the seventh decade. As they occur with approximately equal incidence in people with black skin, Asians and Caucasians, and in people in tropical versus nontropical climates, solar irradiation does not seem to be important in the aetiology.Melanoma of the nail initially presents as a longitudinal pigmented streak. Later, the proximal nail fold may become pigmented—Hutchinson's sign. Even later, the nail plate is destroyed. By this stage the disease is often advanced, with lymph node metastasis frequently present. If nail melanoma is suspected, refer to a dermatologist.

Brittle nails Brittle nails is an age-related phenomenon. The condition is exacerbated by wear and tear and, in particular, frequent immersion in water. Although numerous cosmetics are promoted to treat this, none can be recommended.

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