Nail Psoriasis

Nail psoriasis is involvement of the nail matrix and nail bed in psoriasis, found in up to half of patients with psoriasis and over 80 percent of those with psoriatic arthritis. It is a marker of more severe disease and may precede skin lesions.

• Nail matrix disease causes pitting, leukonychia and crumbling; nail bed disease causes onycholysis, oil drop discolouration, splinter haemorrhages and subungual hyperkeratosis.
• Distal interphalangeal joint arthritis is closely linked to nail involvement.

Fingernail and toenail pitting (irregular, deep), onycholysis with erythematous border, salmon patch (oil drop), subungual hyperkeratosis, splinter haemorrhages, nail plate thickening and crumbling.

• Painful and cosmetically disfiguring; difficulty with fine hand function.
• Differential diagnosis: onychomycosis (tinea unguium), lichen planus, alopecia areata (pitting), eczema, trauma, chronic paronychia, yellow nail syndrome, Darier disease, bacterial infection, subungual melanoma.
• Complications: pain, functional impairment, secondary fungal and bacterial infection, psoriatic arthritis, psychosocial distress.

Clinical with exclusion of fungal infection.

• Nail clippings for KOH, fungal culture and PAS stain; dermoscopy.
• Examine skin, scalp, natal cleft and joints; screen for psoriatic arthritis (dactylitis, enthesitis); cardiovascular risk assessment (lipids, glucose, blood pressure).
• Biopsy of nail bed or matrix for unusual cases.

Choose by number of nails, severity, joint disease and patient priorities.

• Supportive: keep nails short, avoid trauma, wear gloves for wet work, moisturise nail folds, cover or lacquer nails, stop smoking, weight loss, limit alcohol.
• Pharmacological, topical: clobetasol propionate 0.05 percent or calcipotriol 0.005 percent with betamethasone 0.05 percent applied to the nail folds and under the nail edge once daily for 6 months; tacrolimus 0.1 percent ointment twice daily; tazarotene 0.1 percent gel at night. Intralesional triamcinolone acetonide 10 mg/mL into the proximal nail fold, 0.1 mL per site, every 4 to 6 weeks for up to 6 injections. Systemic for severe nail disease or joint involvement: methotrexate 7.5 to 25 mg once weekly with folic acid 5 mg once weekly; acitretin 25 to 30 mg daily; ciclosporin 2.5 to 5 mg/kg/day; apremilast 30 mg twice daily; biological agents such as adalimumab 40 mg every 2 weeks, secukinumab 300 mg monthly, or ixekizumab, where available.
• Procedures: narrowband UVB, PUVA to hands; nail debridement; pulsed dye laser.
• Special groups: pregnancy, topical steroids and emollients only; avoid methotrexate, acitretin and apremilast; certolizumab pegol if biological therapy is essential; children, topical therapy; liver disease, avoid methotrexate and acitretin.
• Red flags: single nail with pigmented band, painful swollen joints or dactylitis, rapid onychodystrophy, suspected secondary infection.
• Follow-up: review at 3 and 6 months; monitor liver tests, full blood count and creatinine every 3 months on methotrexate; repeat cardiovascular risk review yearly.