Nail Psoriasis – Causes, Symptoms and Treatment

What is Nail Psoriasis?

Nail psoriasis is a specific manifestation of psoriasis that affects the finger and toenails, either in isolation or alongside skin psoriasis. It is estimated that 50 to 80 percent of all people with psoriasis will develop nail involvement at some point during their lifetime. In some cases, the nails may be the only part of the body affected, without any visible skin changes.

Although nail psoriasis is not life-threatening, it can significantly impact the quality of life of those affected, as the nail changes are often cosmetically distressing and can be accompanied by pain and functional limitations.

Causes and Risk Factors

Nail psoriasis is caused by a dysfunction of the immune system in which T-lymphocytes (a type of white blood cell) mistakenly attack healthy nail tissue. This leads to excessive cell proliferation in the nail matrix and nail bed.

• Genetic predisposition: Psoriasis has a strong hereditary component. Certain genes, particularly within the HLA system, increase the risk of developing the condition.
• Immunological factors: Overactivity of inflammatory mediators such as TNF-alpha, interleukin-17, and interleukin-23 plays a central role.
• Trigger factors: Stress, infections (e.g., streptococcal infections), nail injuries (Koebner phenomenon), certain medications (e.g., beta-blockers, lithium), and smoking can trigger or worsen flare-ups.
• Psoriatic arthritis: Nail psoriasis is frequently associated with psoriatic arthritis and may be an early warning sign of joint involvement.

Symptoms

Nail psoriasis can present in various clinical forms depending on which nail structure is affected:

Changes Due to Nail Matrix Involvement

• Nail pitting: Small, pit-like depressions on the nail plate – a hallmark sign of nail psoriasis.
• Leukonychia: White spots or discoloration of the nail plate.
• Red spots in the lunula: Reddish discoloration in the half-moon-shaped white area at the base of the nail.
• Crumbling nails: The nail plate becomes brittle, rough, and may crumble.

Changes Due to Nail Bed Involvement

• Oil drop sign: Yellowish-brown discoloration beneath the nail plate, resembling drops of oil.
• Onycholysis: Separation of the nail plate from the nail bed, beginning at the free edge of the nail.
• Subungual hyperkeratosis: Thickening of the skin beneath the nail, causing the nail to lift.
• Splinter hemorrhages: Small, longitudinal bleeding streaks beneath the nail plate.

Diagnosis

The diagnosis of nail psoriasis is primarily clinical, meaning it is based on the assessment of the characteristic appearance by a dermatologist. Additional investigations may be necessary to rule out other conditions.

• Dermoscopy: A magnified examination of the nail that can reveal fine changes such as capillary bleeding.
• Nail biopsy: In unclear cases, a tissue sample may be taken to confirm the diagnosis histologically.
• Fungal culture / mycological swab: To rule out a fungal nail infection (onychomycosis), which can cause similar symptoms.
• NAPSI score: The Nail Psoriasis Severity Index (NAPSI) is a standardized scoring system used to quantify the severity of nail changes and guide treatment planning.

Treatment

Treatment of nail psoriasis depends on the severity of the condition and the presence of concurrent skin psoriasis or psoriatic arthritis. A complete cure is currently not possible, but symptoms can be significantly reduced.

Topical Therapy

• Corticosteroids: Anti-inflammatory creams or solutions applied directly to the nail or cuticle.
• Vitamin D3 analogues (e.g., calcipotriol): Regulate cell growth and reduce inflammation.
• Combination products: Combinations of corticosteroids and vitamin D3 analogues often show greater efficacy.
• Tacrolimus: A topical immunosuppressant used as an alternative to corticosteroids.

Systemic Therapy

In severe cases or when joint involvement is present, systemic medications are used:

• Methotrexate (MTX): A classic immunosuppressive drug that inhibits cell proliferation.
• Ciclosporin: An immunosuppressant used for short-term treatment phases.
• Biologics: Modern antibody-based therapies that specifically target inflammatory mediators (e.g., TNF-alpha inhibitors such as adalimumab, IL-17 inhibitors such as secukinumab, IL-23 inhibitors such as guselkumab). Biologics show particularly good results for nail psoriasis.
• JAK inhibitors: Newer oral agents (e.g., tofacitinib, upadacitinib) that inhibit intracellular inflammatory signaling pathways.

Intralesional Injections

Direct injections of corticosteroids (e.g., triamcinolone) into the nail matrix or nail bed can be locally effective, but are painful and require specialist administration.

Physical Therapy

• PUVA therapy (photochemotherapy): A combination of a photosensitizing agent (psoralen) and UVA irradiation.
• Laser therapy: Pulsed dye laser or excimer laser may be used for isolated nail psoriasis.

General Care Recommendations

• Keep nails short and avoid trauma to the nails.
• Use moisturizing nail products or emollients to protect the nail plate.
• Avoid contact with cleaning agents and harsh chemicals – wear protective gloves if necessary.
• Refrain from nail biting and avoid putting excessive pressure on the nails.

References

1. Crowley J. J. et al. - Treatment of nail psoriasis: best practice recommendations from the Medical Board of the National Psoriasis Foundation. JAMA Dermatology, 2015.
2. Radtke M. A. et al. - Nail psoriasis: clinical features, diagnosis and therapy. Deutsches Ärzteblatt International, 2013.
3. World Health Organization (WHO) - Global report on psoriasis. WHO Press, Geneva, 2016.