Nail psoriasis

What is nail psoriasis?

Nail psoriasis is nail disease associated with psoriasis. It is also known as psoriatic nail dystrophy.

Who gets nail psoriasis?

Only 5% of patients present with typical nail psoriasis as an isolated disorder; most patients have chronic plaque psoriasis. About 50–80% have psoriatic arthritis, particularly arthritis mutilans.

Patients with nail psoriasis may be of any age or race. Nail dystrophy is often precipitated or aggravated by trauma.

What causes nail psoriasis?

Nail psoriasis arises within the nail matrix. The specific pathogenesis of nail psoriasis is unknown.

What are the clinical features of nail psoriasis?

Nail psoriasis can affect any part of one or more nails. There are often scaly plaques on the dorsum of the hands and fingers due to associated plaque psoriasis. Signs depend on the part of the nail affected. Its severity may or may not reflect the severity of the skin or joint psoriasis.

• Psoriasis can enhance the speed of nail growth and thickness of the nail plate.
• Pitting is a sign of partial loss of cells from the surface of the nail plate. It is due to psoriasis in the proximal nail matrix.
• Leukonychia (areas of white nail plate) is due to parakeratosis within the body of the nail plate and is due to psoriasis in the mid-matrix.
• Onycholysis describes the separation of the nail plate from the underlying nail bed and hyponychium. The affected distal nail plate appears white or yellow.
• Oil drop or salmon patch is a translucent yellow-red discolouration in the nail bed proximal to onycholysis. It reflects inflammation and can be tender.
• Subungual hyperkeratosis is scaling under the nail due to excessive proliferation of keratinocytes in the nail bed and hyponychium.
• Transverse lines and ridges are due to intermittent inflammation causing growth arrest followed by hyperproliferation in the proximal nail matrix. The lines and ridges move out distally as the nail grows.
• Psoriatic inflammation can also lead to nail plate crumbling, splinter haemorrhages, and a spotted lunula.
• Acrodermatitis continua of Hallopeau is a rare pustular eruption that affects nail bed, nail matrix and tips of digits.

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Complications of nail psoriasis

Nail psoriasis is unsightly. It can also lead to:

• Pain and tenderness
• Functional disability
• Psychological distress
• Secondary bacterial infection (acute paronychia) or fungal infection (chronic paronychia, onychomycosis).

How is nail psoriasis diagnosed?

Psoriatic nail disease is readily recognised in a patient with current or prior chronic plaque psoriasis. It is frequently confused with fungal nail infection. Fungal infection can also complicate nail psoriasis.

If in doubt, or antifungal treatment is planned, nail clippings and scrapings of subungual debris should be sent for potassium hydroxide microscopy and fungal culture.

A biopsy of the proximal nail matrix is occasionally needed to confirm the diagnosis of nail psoriasis, particularly if dystrophy affects a single nail and a tumour is a possible explanation. The biopsy can lead to permanent nail deformity.

What is the treatment for nail psoriasis?

It is difficult to treat nail psoriasis effectively.

Topical treatment must be applied to the nail matrix and hyponychium for months or years, and its effects are often disappointing. Options include:

• Calcipotriol solution twice daily
• Topical high-potency corticosteroid solution or ointment as weekend pulses under cellophane occlusion at night
• Clobetasol propionate 8% in a lacquer vehicle twice daily for 3 weeks then twice weekly 
• 5-fluorouracil cream twice daily.

Other options include:

• Intralesional triamcinolone acetonide injections into proximal nail folds; this is painful
• Localised phototherapy with UVB or photochemotherapy (PUVA)
• Systemic treatment with methotrexate, acitretin, ciclosporin and biologics.

Note: acitretin thins the nail plate and reduces its speed of growth, which can be helpful or not, depending on the type of nail psoriasis.

Topical and oral antifungal treatment may be prescribed if fungal infection is present.

Chemical or surgical avulsion therapy, i.e. complete removal of the nail, is occasionally recommended. A risk is that the regrowing nail may be as bad, or more severely affected than prior to the procedure.

How can nail psoriasis be prevented?

At this time, we do not know how to prevent nail psoriasis. Avoidance of trauma is essential.

What is the outlook for nail psoriasis?

Nail psoriasis varies in severity over time. In some patients, it resolves completely spontaneously or as a response to systemic treatment. In others, it persists long term.