Psoriatic onychodystrophy
Other names	Psoriatic nails
Psoriasis of the toenails
Specialty	Dermatology
Causes	Psoriasis
Differential diagnosis	Onychomycosis
Treatment	Medications, radiation
Frequency	10% to 78% of those with psoriasis

Psoriatic onychodystrophy or psoriatic nails is a nail disease. It is common in those with psoriasis, with reported incidences varying from 10% to 78%. Elderly patients and those with psoriatic arthritis are more likely to have psoriatic nails.^{[1]: 781–2}

Psoriatic nails are characterized by a translucent discolouration in the nail bed that resembles a drop of oil beneath the nail plate.^[2] Early signs that may accompany the "oil drop" include thickening of the lateral edges of the nail bed with or without resultant flattening or concavity of the nail; separation of the nail from the underlying nail bed, often in thin streaks from the tip-edge to the cuticle; sharp peaked "roof-ridge" raised lines from cuticle to tip; or separation of superficial layers of the nail followed by loss of patches of these superficial layers, leaving thin red nails beneath; or nail pitting–punctate changes along the nail plate surface.

The causes of nail psoriasis are unknown. It has been suggested that fungi may play a role.^[3]

The Nail Psoriasis Severity Index (NAPSI) is a numeric, reproducible, objective, simple tool for evaluation of nail psoriasis.^[4] It evaluates several signs separately, each on a 1–3 scale: pitting, Beau's lines, subungual hyperkeratosis and onycholysis. A 2005 study proposed a modified NAPSI scale for persons with psoriasis and named the title of their publication "Modification of the Nail Psoriasis Severity Index".^[5] Then, in 2007, a study found that there was a high level of inter-rater variability of the 2003 NAPSI scale and proposed another index which was, like the 2005 article, a modification of the 2003 article, and was named modified NAPSI.^[6]

A 2008 study found that Cannavo's qualitative system^[7] correlated with NAPSI (p<0.001) and is less time-consuming.^[8]

There is a risk of misdiagnosis with onychomycosis.

There exist numerous treatments for nail psoriasis but there is little information concerning their effectiveness and safety.^[9] Treatments include topical, intralesional, radiation, systemic, and combination therapies.

• Tacalcitol ointment^[10] obtains a significant improvement in all nail parameters, both of the matrix and of the bed.
• Clobetasol nail lacquer and tacalcitol ointment^[11]
• 5-fluorouracil. A reported side-effect is yellow nails^[12]
• Calcipotriol^[13]
• Calcipotriol plus betamethasone dipropionate ointment.^[14]
• Efalizumab^[15]
• Infliximab^[16]
• Golimumab^[17]
• Low dose methotrexate^[18]
• Intralesional corticosteroid injection^[19]

Available studies lack sufficient power to extrapolate a standardized therapeutic regimen.^[9]

As of April 2009, ^{[needs update]} an assessment of the evidence for the efficacy and safety of the treatments for nail psoriasis is in progress.^[20]

• Infliximab appears to be the most effective treatment for nail psoriasis to date.^[21]
• Results from low-dose acitretin therapy show NAPSI score reductions comparable with those studies evaluating biologic drugs for nail psoriasis and suggest that low-dose systemic acitretin should be considered in the treatment of nail psoriasis.^[21]

A 2013 meta-analysis showed improvement of nail psoriasis with infliximab, golimumab, superficial radiotherapy, electron beam, and grenz rays compared to placebo.^[22] Although systemic therapies have been shown to be beneficial, they may have serious adverse effects.^[22] Topical treatments have not been well studied but may be beneficial.^[22]

Active clinical trials investigating nail psoriasis:^[23]

• Effects of Etanercept.^[24]
• Effects of Golimumab.^[17]

• Dose response and safety of topical Methotrexate.^[25]

• Psoriasis
• Nail disease

• Nail psoriasis at Medscape