What diagnostic tests are recommended to choose a treatment for trachyonychia?

Diagnostic Tests for Trachyonychia Treatment Selection

Nail matrix biopsy is the most definitive diagnostic test to determine appropriate treatment for trachyonychia, as it can identify the underlying cause such as lichen planus, psoriasis, or alopecia areata, which guides specific therapy selection. 1

Understanding Trachyonychia

Trachyonychia ("rough nails") presents as rough, longitudinally ridged nails with a sandy, brittle appearance. It can affect one to all twenty nails and may be:

• Opaque trachyonychia (more common): rough, longitudinally ridged nails
• Shiny trachyonychia (less common): uniform, opalescent nails with pits 2

Essential Diagnostic Tests

1. Nail Matrix Biopsy

• Primary diagnostic test for determining underlying etiology
• Helps differentiate between:
  • Psoriasis (most common finding)
  • Lichen planus
  • Alopecia areata
  • Idiopathic causes 1
• Histological patterns commonly found:
  • Spongiotic pattern (most common)
  • Psoriasiform pattern
  • Lichenoid pattern 1

2. Clinical Examination with Onychoscopy

• Evaluate for specific features:
  • Pitting (present in 80.3% of cases)
  • Koilonychia (45%)
  • Hyperkeratosis (19.6%) 1
• Document number of affected nails (one nail vs. twenty-nail dystrophy)
• Assess for associated dermatological conditions on other body sites

3. Fungal Testing

• Rule out onychomycosis which can mimic trachyonychia:
  • Direct microscopy with potassium hydroxide or calcofluor white
  • Fungal culture
  • PCR-based testing if available 3

4. Bacterial Culture

• If paronychia or secondary infection is suspected:
  • Swab any discharge for culture and sensitivity 3
  • Rule out Pseudomonas (causes green/black discoloration) 3

5. Systemic Disease Evaluation

• Based on clinical suspicion:
  • Immunoglobulin A levels (IgA deficiency association)
  • Atopy evaluation
  • Screening for ichthyosis vulgaris
  • Evaluation for sarcoidosis in adults 4

Treatment Selection Based on Diagnostic Results

For Psoriatic Trachyonychia

• If <3 nails involved: Intralesional triamcinolone acetonide (5-10 mg/cc)
• If >3 nails involved: Consider systemic therapy such as acitretin (0.2-0.4 mg/kg daily) 3

For Lichen Planus Trachyonychia

• Topical steroids ± topical vitamin D analogs
• For severe cases: Intralesional triamcinolone acetonide 3

For Idiopathic Trachyonychia

• In children: Consider observation as spontaneous improvement often occurs within 6 months to 2 years 5
• For cosmetic concerns: Topical steroids under occlusion 1

For Inflammatory Trachyonychia with Paronychia

• Grade 1: Topical povidone iodine 2%, topical antibiotics/corticosteroids
• Grade 2: Add oral antibiotics if infection suspected
• Grade 3: Consider partial nail avulsion in severe cases 3

Important Considerations

1. Pediatric cases: 62% of pediatric trachyonychia cases are idiopathic and often resolve spontaneously, favoring therapeutic abstention 5

2. Biopsy limitations: Nail matrix biopsy may show nonspecific changes even when associated with known dermatological conditions 4

3. Treatment challenges: Many cases remain idiopathic despite thorough evaluation, and treatment may be primarily for cosmetic reasons 1

4. Follow-up: Regular monitoring is essential as treatment response may be slow, requiring 6-12 months for visible improvement

By following this diagnostic approach, clinicians can identify the underlying cause of trachyonychia when possible and select the most appropriate treatment strategy based on etiology, severity, and patient factors.