How should nail fissures be treated, considering possible fungal infection, trauma, or psoriasis?

Treatment of Nail Fissures

For nail fissures, first determine the underlying cause through clinical examination and mycological testing, then treat accordingly: if fungal infection (onychomycosis) is confirmed, use oral terbinafine 250 mg daily for 12-16 weeks for toenails or 6 weeks for fingernails; if psoriasis is the cause, start with high-potency topical corticosteroids with or without calcipotriol, escalating to systemic therapy (adalimumab, etanercept, or ustekinumab) if topical treatment fails; if trauma-related, address the mechanical cause (footwear modification, anatomical correction) and provide supportive nail care.

Diagnostic Approach

Before treating nail fissures, you must differentiate between three primary etiologies:

• Fungal infection (onychomycosis): Obtain nail clippings for potassium hydroxide microscopy and fungal culture before starting any systemic treatment 1
• Psoriasis: Look for nail pitting, oil drop discoloration, subungual hyperkeratosis, and assess for concurrent skin or joint involvement 2
• Mechanical trauma: Examine foot/toe alignment while standing and walking, inspect footwear, and look for anatomical abnormalities (Morton's toe, hallux valgus, flat foot) 3

Critical pitfall: Nearly 50% of nail dystrophy resembles onychomycosis but has other causes 4. Physical trauma is actually more common than fungal infection as a cause of toenail dystrophy 3. Always confirm fungal infection before prescribing potentially toxic systemic antifungals.

Treatment Algorithm by Etiology

If Onychomycosis is Confirmed

For dermatophyte infections (most common):

• First-line: Terbinafine 250 mg daily for 6 weeks (fingernails) or 12-16 weeks (toenails) 1

  • Superior efficacy compared to itraconazole both in vitro and in vivo
  • Requires baseline liver function tests and complete blood count
  • Common adverse effects: headache, taste disturbance, gastrointestinal upset
  • Can aggravate psoriasis (important consideration if psoriasis coexists)

• Alternative: Itraconazole 200 mg daily for 12 weeks continuously, OR pulse therapy 400 mg daily for 1 week per month (2 pulses for fingernails, 3 pulses for toenails) 1

  • Take with food for optimal absorption
  • Monitor hepatic function if therapy exceeds 1 month
  • More drug interactions than terbinafine

For Candida infections:

• First-line: Itraconazole (same dosing as above) for minimum 4 weeks (fingernails) or 12 weeks (toenails) 1
• Alternative: Fluconazole 50 mg daily or 300 mg weekly 1

Adjunctive topical therapy (for mild disease or combination treatment):

• Amorolfine 5% lacquer once or twice weekly for 6-12 months 1
• Ciclopirox 8% lacquer daily for up to 48 weeks 1
• These cure approximately 30% of infections as monotherapy 5

If Psoriasis is the Cause

For isolated nail psoriasis (no significant skin or joint disease):

• Initial treatment: High-potency topical corticosteroids with or without calcipotriol 2
• If topical therapy fails: Consider adalimumab, etanercept, intralesional corticosteroids, ustekinumab, methotrexate, or acitretin 2

For nail psoriasis with significant skin disease:

• Strongly recommended: Adalimumab, etanercept, or ustekinumab 2
• Also recommended: Methotrexate, acitretin, infliximab, or apremilast 2

For nail, skin, AND joint disease:

• Recommended: Adalimumab, etanercept, ustekinumab, infliximab, methotrexate, apremilast, or golimumab 2

If Trauma-Related

Address the mechanical cause:

• Modify or replace ill-fitting footwear 3
• Correct anatomical abnormalities if possible (consider orthopedic referral for Morton's toe, hallux valgus, flat foot) 3
• Keep nails trimmed short 1
• Apply absorbent antifungal powders (miconazole, clotrimazole, tolnaftate) to shoes and feet 1
• Wear cotton, absorbent socks 1

Important consideration: Trauma-induced nail dystrophy predisposes to secondary onychomycosis 3. If mechanical factors are not addressed, nails may remain dystrophic even after treating fungal infection.

Special Populations

Diabetic patients: Treating nail fissures and onychomycosis is crucial to prevent ulcers, osteomyelitis, and amputations 3. These patients are prone to structural foot problems and fungal infections due to hyperglycemia, neuropathy, and vasculopathy.

Immunosuppressed patients: Higher risk of atypical infections and treatment complications. Consider broader differential diagnosis 6.

Monitoring and Prevention

• Assess treatment response at appropriate intervals (e.g., every 6 months for systemic therapy) 7
• For onychomycosis, up to 18 months may be required for complete nail plate regrowth 1
• Prevent reinfection by treating all infected family members simultaneously, disinfecting shoes (naphthalene mothballs in sealed plastic bag for 3 days), and wearing protective footwear in public areas 1
• Recurrence rates for onychomycosis can reach 40-70% without preventive measures 1

Key Clinical Pearls

• Always rule out onychomycosis before treating presumed psoriatic nail disease, as the two conditions frequently coexist and require different management 2, 8
• Nail bed dermoscopy after clipping the detached nail plate can help differentiate psoriatic (thick, white, strongly adherent scales), fungal (yellow-white, moderately adherent, mobile scales), and traumatic (thin, loosely adherent scales) onycholysis 9
• Higher nail psoriasis severity scores (NAPSI) significantly increase odds of concurrent onychomycosis 8
• Terbinafine has lower activity against non-dermatophyte moulds; itraconazole has broader coverage 1