Causes and Treatment of Nail Psoriasis
Nail psoriasis is not "caused" by external factors but rather represents a manifestation of the underlying autoimmune inflammatory disease psoriasis affecting the nail matrix and/or nail bed structures. 1
Pathophysiology
Nail psoriasis occurs when the chronic inflammatory process of psoriasis involves specific anatomical structures of the nail apparatus:
- Nail matrix involvement produces pitting, leukonychia (white spots), red spots in the lunula, and nail plate crumbling 1, 2
- Nail bed involvement results in onycholysis (nail separation), oil-drop discoloration (salmon patches), subungual hyperkeratosis, and splinter hemorrhages 1, 3
- Distal nail bed and hyponychium involvement causes onycholysis 3
- Proximal nail fold involvement leads to psoriatic paronychia 3
The inflammatory cytokines and chemokines driving nail psoriasis appear to be the same as those in psoriatic skin lesions, though the pathogenesis is not fully elucidated. 2
Epidemiology and Clinical Context
- Fingernails are affected in approximately 50% of all psoriasis patients and toenails in 35% 1
- Up to 90% of patients with psoriatic arthritis develop nail changes 1, 2
- There is a striking anatomical and pathophysiologic link between nail psoriasis and psoriatic arthritis, particularly involving the distal interphalangeal joint through entheseal inflammation 4
Critical Diagnostic Consideration
Before initiating any immunosuppressive therapy for nail psoriasis, all patients must be tested for onychomycosis (fungal infection), as these conditions frequently coexist and immunosuppressive treatments will worsen fungal infections. 5 The differential diagnosis between onychomycosis and psoriatic nails can be challenging, requiring direct microscopic examination, fungal culture, or PCR testing when fungal infection is suspected. 1, 6
Treatment Algorithm
For Mild Nail Psoriasis (<3 nails involved):
Start with intralesional triamcinolone acetonide 5-10 mg/cc injected into the nail matrix 1
- For nail bed involvement specifically, add high-potency topical corticosteroids with or without topical vitamin D analogs 1
- This approach is beneficial but may be painful and cannot be applied to many nails 3
For Moderate to Severe Nail Psoriasis (>3 nails involved):
Systemic therapy is required, as topical therapy alone is rarely sufficiently efficient 3
First-line systemic options:
- Acitretin 0.2-0.4 mg/kg daily for extensive nail involvement 1
- Apremilast as a second-line oral option that acts directly on pathogenic inflammatory targets 1, 5
For Severe or Refractory Nail Psoriasis:
Biologic agents are highly effective and represent the most evidence-based approach for severe disease:
- IL-12/23 inhibitor (ustekinumab) or IL-17 inhibitors (secukinumab, ixekizumab) are preferred first-line biologics 1
- TNF inhibitors (infliximab, etanercept, adalimumab, golimumab) are effective second-line options 1, 2
For adalimumab specifically (FDA-approved for nail psoriasis): Initial dose of 80 mg followed by 40 mg every other week starting at week 1. At 26 weeks, 49% of patients achieved ≥2-grade improvement with clear or minimal disease on fingernail assessment, and 47% achieved ≥75% improvement in nail severity scores. 7
Additional Systemic Options:
Important Clinical Caveats
Psoriasis of the nails is recognized as a significant therapeutic challenge with limited evidence for topical therapy efficacy. 1, 4 The more extensive the nail involvement, the more severe the destruction and the greater the impact on quality of life, professional activities, and psychosocial functioning. 3, 4
All systemic treatments that clear widespread skin psoriasis will typically also clear nail lesions, but nail improvement lags behind skin improvement due to the slow growth rate of nails. 3
Patient counseling should include avoidance of stress and mechanical trauma to the nail apparatus, as these can exacerbate disease. 3